# Peak horsepower vs. real horsepower?



## The Warthog (Nov 29, 2010)

I see the term "Peak HP" on some routers. This term makes me a little suspicious, as I remember that "Peak Music Power" was a misleading figure that used to be used to sell amplifiers when I was young. 

If I want a 2HP router, am I really getting 2HP from a router that says "Peak 2HP?"

I took grade 10 science a half century ago, and I remember that a HP is about 750 watts, so I'm not sure how a 15 amp (1650 watt) motor can generate 3¼ HP.


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## bobj3 (Jan 17, 2006)

Hi Roger

It's not the same , speed = HP in this case but with the new routers they have found a way to get around it by letting the motor pull more amps..to a point..at low rpm.to keep the HP up at any speed.

Think of it like your weed wackier very small motor but will tons of HP when the speed comes up (rpm's) ...i.e. the crotch rocket bikes,new table saws as well. 

=========


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## BigJimAK (Mar 13, 2009)

Roger,

The horsepower ratings on routers are technically true, but misleading. First, lets talk about what 3-1/4 hp means. If there are no electrical losses (resistance, friction, heat, etc.) in a motor it takes 746 watts to generate a horsepower. Thus it would take ~2425 watts to generate that much power. In reality there's about 10% wasted due to friction heat, etc. and about 10% lost due to how motors work on AC (in technobabble, the voltage and current waves not being in sync over time). The combined effect is a motor that's in the 80 percent efficient range. At that efficiency, it takes about 25A at 120V to generate 3-1/4hp.

Induction motors behave much differently than induction motors under load. An induction motor delivers its rated power, and that's it. If the load goes up a bit, the motor essentially stops.

With an induction motor, when the load exceeds the rating the motor keeps turning and just draws more and more current (and provides more and more torque) until the resistance in the wiring eventually outweighs the ability for the router to draw more power. 

As the power consumed goes up the heat generated by the router goes up very quickly, exceeding the fans ability to cool it. Additionall, the electronics is rated for certain amounts of current and, if overloaded, can fail as well.

The 3-1/4hp rating is the peak horsepower the motor can generate, as its generating heat much faster than it can reject it. Essentially, as it is burning itself up.

A side-note for when people here are using routers with speed control. As you are slowing down the router, you are slowing down the cooling fan. Does this mean you shouldn't slow down your router? No. Just keep an eye on how warm your router is or isn't getting when you are spinning a large bit taking heavy cuts at slow speed for a long time, as the router may warm up. The cooling system should be designed to take it but you're definitely loading the router more than normal, for two reasons.

Just my $0.02.


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## xplorx4 (Dec 1, 2008)

That was educational, thanks BJ and Jim for the lesson.


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## allthunbs (Jun 22, 2008)

BigJimAK said:


> The 3-1/4hp rating is the peak horsepower the motor can generate, as its generating heat much faster than it can reject it. Essentially, as it is burning itself up.


Hi Jim:

I have just spent several months working with concrete. I cut 80' of concrete (1 1/2" to 4" thick) with several circular saws. Both of which functioned until the smoke was thicker than the concrete dust. I was using a diamond blade so that's a pretty tall order. Then, I used my heaviest electric drills to mix concrete in buckets to refill the holes. They performed until the smoke was thicker than the concrete dust. I stopped before either of the drills seized or caught fire. No such luck for the circular saws. 

How badly does a motor have to smoke before it becomes unusable? Does "just a little bit" of smoke mean that the drill is still usable at full power? Or, does any smoke = total destruction? Or, let it smoke until it seizes, let it cool and go back at it? Or, somewhere in between?

My collection of smoking tools is increasing so I would appreciate your council. Even relegating them to the non-smoking section doesn't seem to help.


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## istracpsboss (Sep 14, 2008)

+1

Perhaps you could explain for me how the North American system works. Unlike most of the rest of the world you are using 120v. How does say, a DW625, differ in the US version from the one the rest of us use running at 230v? How do you get the power from half the voltage without massively uprated circuits? 
In the UK, for instance, standard circuits are 13amp. For something like an oven, there would be a separate 30amp circuit.
Unless you have a weak heart, brief exposure to 13amps won't kill you (don't ask !) but higher powered circuits presumably would. Is the US domestic electrical system inherently more dangerous than that in the rest of the world?


Vaguely relevant, but a personal anecdote:

I was kitting out a laboratory outside Riyad some years ago. It had been built something like 7yrs before, but never commissioned. Saudi had no national grid and voltages varied from town to town, depending on who had sold them the town's power station. Some places that had expanded quickly even had two power stations delivering different voltages to different sides of town !
I checked the voltage plates on various things that were there prior to ordering up all the kit as 120v. Some weeks later, my installation engineer came on in a panic. They had switched on the a/c and things were blowing everywhere. 
In between building the place and my arrival, the town had got a new power station to replace the old US one. Fortunately, none of our stuff had been unpacked and it all went back to the manufacturers to be replaced with 230v stuff.

Cheers

Peter


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## istracpsboss (Sep 14, 2008)

Hi Ron

I would have thought that any smoke was a death sentence. Isn't it the insulation on the windings burning? The windings are going to short, if not at the first puff, not long after.

Cheers

Peter


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## TwoSkies57 (Feb 23, 2009)

Jim....

Accurate and as well explained as anything I've read anywhere else!!


excellent!





BigJimAK said:


> Roger,
> 
> The horsepower ratings on routers are technically true, but misleading. First, lets talk about what 3-1/4 hp means. If there are no electrical losses (resistance, friction, heat, etc.) in a motor it takes 746 watts to generate a horsepower. Thus it would take ~2425 watts to generate that much power. In reality there's about 10% wasted due to friction heat, etc. and about 10% lost due to how motors work on AC (in technobabble, the voltage and current waves not being in sync over time). The combined effect is a motor that's in the 80 percent efficient range. At that efficiency, it takes about 25A at 120V to generate 3-1/4hp.
> 
> ...


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## allthunbs (Jun 22, 2008)

istracpsboss said:


> Hi Ron
> 
> I would have thought that any smoke was a death sentence. Isn't it the insulation on the windings burning? The windings are going to short, if not at the first puff, not long after.
> 
> ...


That's what I'm wondering. Both drills still work. Wondering if it's worth the time to replace brushes and bearings on the cheap Skil saw. I'm not going to waste money on the Porter Cable.


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## kp91 (Sep 10, 2004)

Depending on what was causing the 'smoke'....

sometimes the smoke could be dirt and oil accumulations on the windings of the motor that have finally gotten hot enough to cook off, but not have damaged the insulation itself. Sometimes the smoke is from the shields or seals in the bearings failing and you're starting to burn off the light portion of the grease as it escapes the bearings. Sometimes, the smoke is the insulation itself, and that's the unmistakable smell of electrical death.

Without seeing the color of the smoke, and smelling the smell, it's hard to determine what the cause was.


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## allthunbs (Jun 22, 2008)

kp91 said:


> Sometimes, the smoke is the insulation itself, and that's the unmistakable smell of electrical death.
> 
> Without seeing the color of the smoke, and smelling the smell, it's hard to determine what the cause was.


It was that "unmistakable smell of electrical death" -- sort of gray, acrid, chemical...


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## Cassandra (Mar 15, 2006)

allthunbs said:


> It was that "unmistakable smell of electrical death" -- sort of gray, acrid, chemical...


Hi Ron:

Personally, I would not use that motor again, at least not until the windings were checked out (hi-pot test.) If the insulation is compromised, then it is only a matter of time before voltage will appear on the motor case, causing all sorts of problems. That includes electrocution.

Cassandra


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## bobj3 (Jan 17, 2006)

Hi 

Just my 2 cents

I think it comes down to using the right tool for the job, a power hand saw is not made to cut concrete, they make concrete saws, most are gas power but they do make some big elec.ones also, it's like hooking up a trailer to your VW, what do you thing going to happen..

=======


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## Cassandra (Mar 15, 2006)

bobj3 said:


> Hi
> 
> Just my 2 cents
> 
> ...


Agreed!!


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## The Warthog (Nov 29, 2010)

I understood most of that. So, if I am looking for the most powerful 110v. motor for my router table, am I to look for a high amperage, and ignore the HP rating on the router? That makes a kind of intuitive sense to me.

Thanks again!


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## allthunbs (Jun 22, 2008)

Cassandra said:


> Hi Ron:
> 
> Personally, I would not use that motor again, at least not until the windings were checked out (hi-pot test.) If the insulation is compromised, then it is only a matter of time before voltage will appear on the motor case, causing all sorts of problems. That includes electrocution.
> 
> Cassandra


Hi Cassandra:

Yup, that sounds about right. As for the "right" tool, the circular saws were. You ever try to use a 14" hand held electric concrete saw? Darn near cut my leg off on several occasions. The Makita has an anti binding feature but the only one available was a Hilti and it didn't. Should see that sucka fly - jump ain't the word. Also, the circular saw cuts a 1 1/2" to 2" deep cut. That leaves the remainder of the 4" thick concrete to be broken out by hand. That leaves a "key" when you pour the new concrete. That helps bond the patch to the old concrete. The four inch cut you have to break away and add bonding agents and additives to the replacement concrete.

And, here I was hoping I wouldn't have to talk the wife into a few new tools. Yeah right!


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## bobj3 (Jan 17, 2006)

Hi

At one time I wanted a new door way in the basement, the wall was 10" thick with rebar in it and I called a guy up that did it day in and day out, he said no big deal he did it in 2 hours or less but he said you will need to break it up and take it out of the basement, it cost me a 125.oo bucks but worth every penny, sometime it's worth calling the right guy with the right tools to get the job done.. 


========


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## BigJimAK (Mar 13, 2009)

Ron,

Let's compare induction motors with universal motors. 

Universal motors have a lot going for them. They've got a great power to weight ratio and a great power to price ratio. Most will run on AC or DC power. The down side on these little powerhouses is their ability to cool themselves. 

The induction motor is a different beast. You'll find induction motors in HVAC systems that are expected to run around the clock, year in and year out. They are heavy for their power but are known for their very long lives.

The phrase "right tool for the right job" applies to the universal motor in your situation, Ron. 

There's no reason a universal motor cannot be used to cut concrete, as you've shown. The achilles heel of universal motor tools is they let you push them too hard... they just get hot. They're not really designed to be used where long continuous service is required.

Eighty feet of concrete takes quite a bit of time, far longer that I'd run a universal motor continuously. Its also easy to push one too hard. While I'd prefer an internal combustion engine or induction motor powered saw, you can get there with a universal motor if you monitor the temperature of the motors and either take cooling breaks or swap saws as soon as one starts getting hot and no later than they first start to "smell hot". The "hot smell" (usually) indicates the insulation is starting to break down. Kept running until they smoke its typically the insulation burning. Then it's time to rewind or replace the saw. A saw with burned insulation is subject to complete insulation breakdown. If/when that happens you hope it shorts directly to ground instead of shorting through your body to ground.

There have been a couple of times when I have conciously chosen to abuse a universal motor-driven tool. Both times were when I was at a remote site and chose to "sacrifice" the tool (once a saw, once a small compressor) and both times they went in the trash heap when I got back, once I cut off the power cords.




allthunbs said:


> Hi Jim:
> 
> I have just spent several months working with concrete. I cut 80' of concrete (1 1/2" to 4" thick) with several circular saws. Both of which functioned until the smoke was thicker than the concrete dust. I was using a diamond blade so that's a pretty tall order. Then, I used my heaviest electric drills to mix concrete in buckets to refill the holes. They performed until the smoke was thicker than the concrete dust. I stopped before either of the drills seized or caught fire. No such luck for the circular saws.
> 
> ...


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## BigJimAK (Mar 13, 2009)

The NA residential power standard is 120/240V AC single phase. Technically the 240 is two 120V sources 180* out of phase. This gives you 240V between the two hot legs but only 120 from either hot leg to ground. It was chosen to reduce the risk of electrocution since most "shocks" occur between hot and ground. In the NA home, unless you have a shop, 240V is typically only used for electric stoves, electric clothes dryers, electric water heaters and permanent electric heaters.

Typical home circuit breakers are 20A 120V though some people install 15A breakers to get away with smaller wire (14 vs 12 Ga). 

NA commercial / industrial power is 3-phase, either 120V/208 Wye or 277/480VAC Wye. The power between phases is 120*, which is the reason why the voltage between two 120V hot legs is 208V instead of 240. 

As far as "more dangerous", no... it's arguably safer. What plays in is the rather conservative National Electric Code which is not federally mandated but is typically adopted (with exceptions) by virtually all states.




istracpsboss said:


> +1
> 
> Perhaps you could explain for me how the North American system works. Unlike most of the rest of the world you are using 120v. How does say, a DW625, differ in the US version from the one the rest of us use running at 230v? How do you get the power from half the voltage without massively uprated circuits?
> In the UK, for instance, standard circuits are 13amp. For something like an oven, there would be a separate 30amp circuit.
> ...


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## Cherryville Chuck (Sep 28, 2010)

The Warthog said:


> I see the term "Peak HP" on some routers. This term makes me a little suspicious, as I remember that "Peak Music Power" was a misleading figure that used to be used to sell amplifiers when I was young.
> 
> If I want a 2HP router, am I really getting 2HP from a router that says "Peak 2HP?"
> 
> I took grade 10 science a half century ago, and I remember that a HP is about 750 watts, so I'm not sure how a 15 amp (1650 watt) motor can generate 3¼ HP.


You are correct. Any audiophile wants power measured in watts RMS (root mean square) which is more of an average. Router manufacturers get their machines spinning as fast as they can go and then measure how much energy it takes to stop them (essentially brake HP). The crunch is that power is the ability to do work over time so if you shorten the time to make the armature stop it makes the HP level look good. Watts is a more accurate measure. The only other factor involved then is efficiency which is power out/power in x 100 = % efficiency. A 3 1/4 HP router would have to use over 2200 watts of power which the standard North American circuit cannot deliver. A 15 amp circuit can deliver about 1800 watts of power (line voltage x amps= watts i.e. 15 amps x 120 volts = 1800 watts). I too would like to see a little more truth in advertising.


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## bobj3 (Jan 17, 2006)

Hi

If I run my 3 1/4 HP on a 15amp. breaker it will pop it every time on a full load ,I need to run it on a 20 amp. breaker that is a standard in the states for equipment in the home shop.
15 amp.is for light circuits in the states...

====== 



Cherryville Chuck said:


> You are correct. Any audiophile wants power measured in watts RMS (root mean square) which is more of an average. Router manufacturers get their machines spinning as fast as they can go and then measure how much energy it takes to stop them (essentially brake HP). The crunch is that power is the ability to do work over time so if you shorten the time to make the armature stop it makes the HP level look good. Watts is a more accurate measure. The only other factor involved then is efficiency which is power out/power in x 100 = % efficiency. A 3 1/4 HP router would have to use over 2200 watts of power which the standard North American circuit cannot deliver. A 15 amp circuit can deliver about 1800 watts of power (line voltage x amps= watts i.e. 15 amps x 120 volts = 1800 watts). I too would like to see a little more truth in advertising.


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## crquack (Oct 10, 2008)

> Unless you have a weak heart, brief exposure to 13amps won't kill you (don't ask !)


You must be talking milliseconds! In defibrillation which lasts about 10 milliseconds currents of close to 100A are not unusual.

However, for a longer exposure even 60 mA can induce ventricular fibrillation.

To have 13 A passed through your body, assuming an average impedance (arm-to-arm) of 1500 ohm one would have to be exposed to something like 20,000 volts!


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## harrysin (Jan 15, 2007)

bobj3 said:


> Hi
> 
> If I run my 3 1/4 HP on a 15amp. breaker it will pop it every time on a full load ,I need to run it on a 20 amp. breaker that is a standard in the states for equipment in the home shop.
> 15 amp.is for light circuits in the states...
> ...


Isn't that a good-enough reason for the US to follow most of the rest of the world and change to between 220 and 240 volts. It can be done, in England up to the early fifties, large areas were on DC! Here in Western Australia up to about the eighties voltages ranged between 190 and 260 volts, the latter if you lived close to a sub-station. In those days most equipment had input transformers with adjustable tappings at 200, 220, 240 volts and some 260V. VCR's brought in by holiday makers from Hong Kong and Singapore were for 220 volts and most didn't require step-down transformers in order to perform correctly. Gradually distribution equipment was replaced and now we have a fairly steady 240 volts.


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## BigJimAK (Mar 13, 2009)

I couldn't agree with you more on the 20A breakers, BJ. That router's doing it's "Energizer Bunny" routine. Load it up and it just keeps drawing more and more power and going and going... <g>

As for 15 amp circuits even for lighting, it'd take some special circumstances for me to not run 20A instead. The 15A and 20A breakers sell for the same price, so all it costs extra to run a 20A circuit is to move from 14 ga to 12 ga wire... and the cost of that is chump change... and we're not chumps! 



bobj3 said:


> Hi
> 
> If I run my 3 1/4 HP on a 15amp. breaker it will pop it every time on a full load ,I need to run it on a 20 amp. breaker that is a standard in the states for equipment in the home shop.
> 15 amp.is for light circuits in the states...
> ...


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## bobj3 (Jan 17, 2006)

Hi Jim

I got one for you,,, many of the motors have a plate on them , they show how to rewire the motor for 110/120 or 220 , and some list a 205 hook up ,I have always used the 220 wiring setup..what's with the 205 deal... is it a 50/60 cycle thing.

================= 



BigJimAK said:


> I couldn't agree with you more on the 20A breakers, BJ. That router's doing it's "Energizer Bunny" routine. Load it up and it just keeps drawing more and more power and going and going... <g>
> 
> As for 15 amp circuits even for lighting, it'd take some special circumstances for me to not run 20A instead. The 15A and 20A breakers sell for the same price, so all it costs extra to run a 20A circuit is to move from 14 ga to 12 ga wire... and the cost of that is chump change... and we're not chumps!


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## allthunbs (Jun 22, 2008)

BigJimAK said:


> I couldn't agree with you more on the 20A breakers, BJ. That router's doing it's "Energizer Bunny" routine. Load it up and it just keeps drawing more and more power and going and going... <g>
> 
> As for 15 amp circuits even for lighting, it'd take some special circumstances for me to not run 20A instead. The 15A and 20A breakers sell for the same price, so all it costs extra to run a 20A circuit is to move from 14 ga to 12 ga wire... and the cost of that is chump change... and we're not chumps!


Not all of us are millionaires either. What you might consider "chump change" others might consider the difference between hobby and not. 12/2 is 25% more than 14/2. Also consider that line would be dedicated to that tool and that loop not shared across the shop. Given the number of tools, that's a lot of dedicated lines and a lot of expense, not to mention, upgraded service. 

I have a luxurious shop. I have four power feeds, dust collection, lighting, heat and one 20A tool line. But, my heating costs can be $1,000 in a year. I keep the temperature just above freezing so the tools won't get damaged. I work in that temperature. 

How many guys here run an extension cord out the back door, pull their stuff out of the garden shed and start to work. Those are the guys you don't hear from. How can they compete with their "Saturday shop" against some of the luxurious fully equipped tool collections sometimes represented here. But, those guys are the most creative. Necessity being the mother of invention. It's easy to drop a buck on something. It's a lot harder to craft something from scraps or firewood to save that buck for something more important.

It bothers me when the only solution is to spend money on the latest widget or gadget just because it is easy. It's nice to know, once in a while that a particular tool exists, but a constant stream of it is sometimes quite sickening. 

Not all of us draw the huge salaries some of you fellows do. Some of us had our living stolen from us by people hiding behind guns or national boundaries, or both. So, when you talk about "chump change" consider someone may resent it.


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## Cherryville Chuck (Sep 28, 2010)

bobj3 said:


> Hi
> 
> If I run my 3 1/4 HP on a 15amp. breaker it will pop it every time on a full load ,I need to run it on a 20 amp. breaker that is a standard in the states for equipment in the home shop.
> 15 amp.is for light circuits in the states...
> ...


The standard circuit here in Canada is 15 amp. I had the biggest Freud, until it died, and now am running a Hitachi M12V. I can run the router, and possibly a light bulb or 2, and never blow a breaker even with the router under heavy load. I am not sure why you aren't able to do that with a 15 amp circuit there.

I know you like to say that speed equals power but that really isn't the case. Speed only has to do with momentum where momentum= mass x velocity . Momentum is a measure of stored energy. Because a router armature is relatively light and has a small diameter, it is incapable of storing any meaningful amount of energy. The definition of power is the ability to do work (move a mass over a distance) in a specified time interval, or, the energy that is capable of doing the work. There is no provision for speed in that. For that you need HP which is the ability to move 33,000 lbs x 1foot in one minute or a watt which is 1/746 HP.


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## BigJimAK (Mar 13, 2009)

Let me put my use of "chump change" in perspective. A 25' roll of 12/2 sells for $10.48 at HD.

Southwire 14-2 Romex SIMpull NM-B 25' - 56753321 at The Home Depot

Based on Ron's "25% more" it would cost an extra $2.62 for a one-time investment in upgrading your wiring. 

No offense was intended; perform your own cost/benefit analysis and come to your own conclusion, folks. Your mileage may vary.

I ask that anyone who took offense to my post please PM me (except Ron, who has already expressed himself) as I'd appreciate the opportunity to apologize personally.




allthunbs said:


> Not all of us are millionaires either. What you might consider "chump change" others might consider the difference between hobby and not. 12/2 is 25% more than 14/2. Also consider that line would be dedicated to that tool and that loop not shared across the shop. Given the number of tools, that's a lot of dedicated lines and a lot of expense, not to mention, upgraded service.
> 
> I have a luxurious shop. I have four power feeds, dust collection, lighting, heat and one 20A tool line. But, my heating costs can be $1,000 in a year. I keep the temperature just above freezing so the tools won't get damaged. I work in that temperature.
> 
> ...


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## BigJimAK (Mar 13, 2009)

bobj3 said:


> Hi Jim
> 
> I got one for you,,, many of the motors have a plate on them , they show how to rewire the motor for 110/120 or 220 , and some list a 205 hook up ,I have always used the 220 wiring setup..what's with the 205 deal... is it a 50/60 cycle thing.
> 
> =================


I haven't seen a 205 before, Bob. Could it be a scratched-out 208? I've seen that plenty. The 208 would be what you'd find in your typical commercial property / strip mall.

Of course it could be the 110V - 115V - 120V thing... ???


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## bobj3 (Jan 17, 2006)

Hi Chuck

I also have the Hitachi M12V tank and out of the 8 tank routers I have the Hitachi M12V will pop the breaker every time if I ask it to run at top speed and pull a full load, I did replace the breaker in the panel box thinking it maybe the breaker but no luck it will still pop the breaker, I think it's bad design in the motor winding I guess , I took the router to a mates house and it did the same thing..as you can see I'm not real big fan of the Hitachi M12V.. if I plug it into a hotshot 20amp.line out of the breaker panel it will let the router at full power but that's a PITA the norm..
Like many shops I have other things plugged in the normal 20 amp. line all the time i.e. radio,chargers,light or two,remote control, all pulling a little bit,etc.

======



Cherryville Chuck said:


> The standard circuit here in Canada is 15 amp. I had the biggest Freud, until it died, and now am running a Hitachi M12V. I can run the router, and possibly a light bulb or 2, and never blow a breaker even with the router under heavy load. I am not sure why you aren't able to do that with a 15 amp circuit there.
> 
> I know you like to say that speed equals power but that really isn't the case. Speed only has to do with momentum where momentum= mass x velocity . Momentum is a measure of stored energy. Because a router armature is relatively light and has a small diameter, it is incapable of storing any meaningful amount of energy. The definition of power is the ability to do work (move a mass over a distance) in a specified time interval, or, the energy that is capable of doing the work. There is no provision for speed in that. For that you need HP which is the ability to move 33,000 lbs x 1foot in one minute or a watt which is 1/746 HP.


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## bobj3 (Jan 17, 2006)

Hi Jim

I think it is a 208 thing, I was just using my recall of seeing it the last time I had the cover off , 5 or 6 years ago on a 5HP compress motor..some small things don't stick that well as you get older  but I do recall seeing the little metal tag on the wire saying 208 line..

==========
'


BigJimAK said:


> I haven't seen a 205 before, Bob. Could it be a scratched-out 208? I've seen that plenty. The 208 would be what you'd find in your typical commercial property / strip mall.
> 
> Of course it could be the 110V - 115V - 120V thing... ???


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## bobj3 (Jan 17, 2006)

Hi

Wire size in the shop, I used 10/3 for most of my wiring in the shop, this is one place you don't want to go cheap but you don't want to get your wire from HD/Lowes, I always buy that type of stuff from Cash Way Elec.Supply or some other Elec.Supply outlet the place that HD/Lowes gets it from went they run out or short.

That's a little tip always read the box that they have in the stores you will sometimes see it on the box where they got it from...

=====

=======


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## Cassandra (Mar 15, 2006)

bobj3 said:


> Hi
> 
> Wire size in the shop, I used 10/3 for most of my wiring in the shop, this is one place you don't want to go cheap but you don't want to get your wire from HD/Lowes, I always buy that type of stuff from Cash Way Elec.Supply or some other Elec.Supply outlet the place that HD/Lowes gets it from went they run out or short.
> 
> ...


"A chain is as strong as its weakest link."

Nothing wrong with oversizing the wire. It reduces the voltage drop along the wire, for a given load. Less voltage sag when a heavy electrical load starts (such as a 3-1/4 HP router.)

However, one needs to consider where the weakest link is. If one runs power from the main power panel to a sub-panel ("pony panel"), best to oversize the run between the panels, in addition to the individual loads on the pony panel.

Cassandra'


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## Cassandra (Mar 15, 2006)

BigJimAK said:


> Of course it could be the 110V - 115V - 120V thing... ???


It's that annoying historical "nominal" rating crap. I have seen the nominal rating at 110, 112, 115, 117, and 120. Fortunate the electrical code I have to follow specifies that the engineer is to use 120V for calculations. 

The one thing that keeps me happy with using the 120V rating is measuring the line voltage with a peak reading meter and it says 169V. Calculation then shows me that the line voltage is close to the 120Vrms, assuming a sine wave.

Cassandra


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## BigJimAK (Mar 13, 2009)

The biggest obstacle with that, Harry, is that most US electrical appliances are not dual voltage. Tools aside, it's only the ones serving dual markets (US and elsewhere) and even then only voltage insensitive products or those expensive enough to warrant dual voltage transformers. Even for those insensitive devices, people would have to change the plug on all of their existing appliances to protect people from unsafely plugging a 120-only device into 240.



harrysin said:


> Isn't that a good-enough reason for the US to follow most of the rest of the world and change to between 220 and 240 volts. It can be done, in England up to the early fifties, large areas were on DC! Here in Western Australia up to about the eighties voltages ranged between 190 and 260 volts, the latter if you lived close to a sub-station. In those days most equipment had input transformers with adjustable tappings at 200, 220, 240 volts and some 260V. VCR's brought in by holiday makers from Hong Kong and Singapore were for 220 volts and most didn't require step-down transformers in order to perform correctly. Gradually distribution equipment was replaced and now we have a fairly steady 240 volts.


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## bobj3 (Jan 17, 2006)

HI Cassandra

My shop power comes in right off the power pole no sub panel..  it has it's own meter that I use to get the bottom line to do the workup on a job now and than like welding jobs.  that can get the meter going right off the wall 



=========





Cassandra said:


> "A chain is as strong as its weakest link."
> 
> Nothing wrong with oversizing the wire. It reduces the voltage drop along the wire, for a given load. Less voltage sag when a heavy electrical load starts (such as a 3-1/4 HP router.)
> 
> ...


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## Cassandra (Mar 15, 2006)

bobj3 said:


> HI Cassandra
> 
> My shop power comes in right off the power pole no sub panel..  it has it's own meter that I use to get the bottom line to do the workup on a job now and than like welding jobs.  that can get the meter going right off the wall
> 
> ...


Obviously you're not in Ontario. Getting a second metered point on a property can be a royal pain in the proverbial here.


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## bobj3 (Jan 17, 2006)

HI Jim

Talk about the Metic night male how about every appliance in the states going pop ,we don't have the fire departments to take care of all the homes going up in smoke...


==========



BigJimAK said:


> The biggest obstacle with that, Harry, is that most US electrical appliances are not dual voltage. Tools aside, it's only the ones serving dual markets (US and elsewhere) and even then only voltage insensitive products or those expensive enough to warrant dual voltage transformers. Even for those insensitive devices, people would have to change the plug on all of their existing appliances to protect people from unsafely plugging a 120-only device into 240.


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## bobj3 (Jan 17, 2006)

Hi Cassandra

No big deal in the states, Many homes have them just for the asking.
Just about all apartments have them...  my meter is listed by the address and the 1/2 . i.e. xxxxx street address , xxxx1/2 street address...


=========



Cassandra said:


> Obviously you're not in Ontario. Getting a second metered point on a property can be a royal pain in the proverbial here.


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## crquack (Oct 10, 2008)

> I know you like to say that speed equals power but that really isn't the case.


Quite right. Power = speed (rpm) x *torque* x constant (unit-dependent).


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## harrysin (Jan 15, 2007)

BigJimAK said:


> The biggest obstacle with that, Harry, is that most US electrical appliances are not dual voltage. Tools aside, it's only the ones serving dual markets (US and elsewhere) and even then only voltage insensitive products or those expensive enough to warrant dual voltage transformers. Even for those insensitive devices, people would have to change the plug on all of their existing appliances to protect people from unsafely plugging a 120-only device into 240.


My memory tells me that when the changeover from DC occurred in England, the government paid for modification where possible or replacement of appliances. Here in Australia not many years ago in an effort to remove guns from the streets, the government introduced a buy-back scheme whereby they paid market value for guns handed in. As we lead up to the analogue TV switch-off, the government is supplying Digital set top boxes for free and when the time arrives, will pay for a technician to make a house call where necessary.
I therefore see no reason why the US government couldn't pay for whatever was necessary for such a changeover, and if lack of money is quoted as an excuse, then I doubt that there are many American citizens who wouldn't be able to tell your President how and where to find not only enough for changeover to 220 volts, but also enough to solve many other problems, not the least of which I gather is the health care system.
The above paragraph is in no way intended as "America bashing" and as for governments finding money, ours is no different, we find money to give immediate housing to so called refugees whilst thousands of Australians have to wait years for a state rental home. Our government is about to introduce a new tax to help pay for re-building flooded Queensland instead of reducing the billions of dollars given each year to far away countries, and I wonder how much of it actually reaches the people it's intended for.


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## Cherryville Chuck (Sep 28, 2010)

crquack said:


> Quite right. Power = speed (rpm) x *torque* x constant (unit-dependent).


I think the formula you are refering to is Power= torque x 2pi x rpm/60. Your formula does pass the test for power, i.e. work/time. To put the importance of rpm in perspective try the following test. Turn on your router and get it revved up as fast as it will go. Now shut it off. It stayed in motion under zero load for about 3 to 5 seconds. Once the power was turned off torque went to zero. The 3-5 seconds that the armature kept spinning (under zero load) is the power that was still available due to rotational energy (stored energy or inertia). The formula you quoted is for total energy in the system (i.e. torque, which is constant under a constant load, and rotational energy, which was imparted to the armature by the initial torque that was applied to it.) As I already pointed out, a router armature is too light and has too small a moment arm (diameter) to be able to store any significant amount of energy. If you want power, you need input watts. RPM has almost nothing to do with it no matter how fast you can spin the armature.


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## crquack (Oct 10, 2008)

> Power= torque x 2pi x rpm/60.


2pi/60 being the constant which has to be modified further depending on the units.



> If you want power, you need input watts.


Yes, that is true of any system that converts one form of power to another.


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## Joesf (Nov 27, 2010)

"With an induction motor, when the load exceeds the rating the motor keeps turning and just draws more and more current (and provides more and more torque) until the resistance in the wiring eventually outweighs the ability for the router to draw more power. "

Assuming excellent 80 percent efficiency there is no way you can get more than 2.57 HP out of a 20 amp circuit since the circuit blows at 20 amps. So where is the 3.25 HP? It is not possible.


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## bobj3 (Jan 17, 2006)

Hi Joe

You and some of the members on the north side of the border think the same way , maybe you should tell the mfg. of the 3 1/2HP routers and some 3HP table saws ,they have got it wrong ,they sure sale a ton of them..I don't recall anyone suing for false advertisement  many of the 3HP routers items are rated 15amp. by the way..

My table saw as a sticky on it and that states , developing 3 HP., and it's rated at 12 amp.maybe it's the 10" saw blade mass ..

======



Joesf said:


> "With an induction motor, when the load exceeds the rating the motor keeps turning and just draws more and more current (and provides more and more torque) until the resistance in the wiring eventually outweighs the ability for the router to draw more power. "
> 
> Assuming excellent 80 percent efficiency there is no way you can get more than 2.57 HP out of a 20 amp circuit since the circuit blows at 20 amps. So where is the 3.25 HP? It is not possible.


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## walowan (Jan 21, 2011)

The scientific formula for horse power vs electrical energy is:

1 horsepower = 745.699872 watts

that may or may not be what manufacturers are using for thier ratings.

watts = volts x amps , what are the manufactureres using for amps? A locked rotor?


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## Cherryville Chuck (Sep 28, 2010)

Joesf said:


> "With an induction motor, when the load exceeds the rating the motor keeps turning and just draws more and more current (and provides more and more torque) until the resistance in the wiring eventually outweighs the ability for the router to draw more power. "
> 
> Assuming excellent 80 percent efficiency there is no way you can get more than 2.57 HP out of a 20 amp circuit since the circuit blows at 20 amps. So where is the 3.25 HP? It is not possible.


You are absolutely correct Joe. I believe that the figures they give are for "brake horsepower" the amount of work required to stop the router once it is in motion. Since work is measured over time, if you shorten the amount of time to stop the arbor, you may be able to quote the HP ratings they give.


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## Cherryville Chuck (Sep 28, 2010)

bobj3 said:


> Hi Joe
> 
> You and some of the members on the north side of the border think the same way , maybe you should tell the mfg. of the 3 1/2HP routers and some 3HP table saws ,they have got it wrong ,they sure sale a ton of them..I don't recall anyone suing for false advertisement  many of the 3HP routers items are rated 15amp. by the way..
> 
> ...


If you have a 3 HP table saw, it is working on 220v which would be the equivalent of 24 amps at 110v which will get you into that 3HP wattage range. The saw blade is stored energy and only applies if they are doing a brake horsepower measurement because the spinning blade retains energy. Unlike a router armature and bit, the 10" saw blade has a much longer "moment arm" and much greater mass and is capable of storing quite a bit of energy and therefore able to do some work before the energy drops to zero. That's why the manufacturers put brakes on them.


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## allthunbs (Jun 22, 2008)

Cherryville Chuck said:


> If you have a 3 HP table saw...


As usual Charles, your response is knowing and insightful. Thank you for the clarity.

Is there a real relationship between actual horsepower and "brake horsepower" or is it totally relative to the time and effort needed to stop the armature?

Michael:

Thanks for the HP formula. I've always used 750 watts per HP as a general rule of thumb but the actual number is nice to have handy.


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## bobj3 (Jan 17, 2006)

Hi Charles

Thanks.. But it's 120 volt table saw..and can't be rewire for 220v. 120 volts only, no brakes on my saw that I know about..

=========



Cherryville Chuck said:


> If you have a 3 HP table saw, it is working on 220v which would be the equivalent of 24 amps at 110v which will get you into that 3HP wattage range. The saw blade is stored energy and only applies if they are doing a brake horsepower measurement because the spinning blade retains energy. Unlike a router armature and bit, the 10" saw blade has a much longer "moment arm" and much greater mass and is capable of storing quite a bit of energy and therefore able to do some work before the energy drops to zero. That's why the manufacturers put brakes on them.


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## paduke (Mar 28, 2010)

Harry
I dont want the goverment messing with anything!!!!! I receive few benefits and pay more taxes. Anytime goverment does something it alwasy costs more than if they just left it alone So rgarding power transmissions they already have it overregulated and now you want to give them more control. Wake up goverment takes your freedom everytime you take a handout 

God Bless
Bill


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## BigJimAK (Mar 13, 2009)

*A Clarification on Brake Horsepower*



bobj3 said:


> no brakes on my saw that I know about..
> 
> =========


None on mine either, BJ... <g>



According to the Encyclopedia Brittanica: "Horsepower at the output shaft of an engine, turbine, or motor is termed brake horsepower or shaft horsepower, depending on what kind of instrument is used to measure it."

brake horsepower (engineering) -- Britannica Online Encyclopedia


According to the Engineering Toolbox (a well regarded reference on the engineering comminity): "
*Shaft or Brake Horsepower*

The brake horsepower is the amount of real horsepower going to the pump, not the horsepower used by the motor. In the metric system kilowatts (kW) is used.
"

Pumps, Fans and Turbines - Horsepower


According to Wikipedia: "Brake horsepower
Brake horsepower (bhp) is the measure of an engine's horsepower before the loss in power caused by the gearbox, alternator, differential, water pump, and other auxiliary components such as power steering pump, muffled exhaust system, etc. _Brake_ refers to a device which was used to load an engine and hold it at a desired RPM. During testing, the output torque and rotational speed were measured to determine the _brake horsepower_. Horsepower was originally measured and calculated by use of the indicator (a James Watt invention of the late 18th century), and later by means of a De Prony brake connected to the engine's output shaft. More recently, an engine dynamometer is used instead of a De Prony brake. The output delivered to the driving wheels is less than that obtainable at the engine's crankshaft.
"

Horsepower - Wikipedia, the free encyclopedia

According to WiseGeek: "
Brake horsepower (BHP) is the amount of work generated by a motor without taking into consideration any of the various auxiliary components that may slow down the actual speed of the motor. Sometimes referred to as pure horsepower, brake horsepower is measured within the engine’s output shaft. Depending on the configuration of the engine, the point on the output shaft that is the focus of the measurement is the engine dynamometer. 
The reference to this type of horsepower measurement as brake horsepower has its origins in the braking systems that were used on some of the first automobiles in the early twentieth century. In many instances, cars were equipped with a hand brake that would slow the forward projection of the vehicle. This same hand brake was also used in the manufacturing process to gauge the amount of torque created within the motor, making sure the output was within acceptable limits."

What Is Brake Horsepower?


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## Cherryville Chuck (Sep 28, 2010)

Thanks for the explanationation on that Jim. I had grown up using perhaps the wrong term to describe what I was attempting to convey. It may have been a regional difference. I know that when I took my air brake course many years ago in British Columbia, we were told that an air brake system was required to produce a stopping force of 50 brake horsepower per wheel. This type of definition is more in line with what I was describing. In the meantime, I have found an excellent article on the web that explains this whole issue of Peak HP vs Actual HP very thoroughly and explains what I was trying to describe. It can be found at

http://www.kevinsbrady.net/motors.pdf

In the article there is a chart that shows real horsepower according to amperage draw and motor efficiency. 

Bob,
If your saw is only 110-120vac then it is only a true 1hp according to the above article. My Unisaw is rated at 3 hp and it can't be run on anything but 220-240vac so one manufacturer is lying (actually maybe they both are, one just less than the other). By the way, my Unisaw must have some kind of brake as it stops much quicker than the old Rockwell Beaver 10" I have.


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## crquack (Oct 10, 2008)

> http://www.kevinsbrady.net/motors.pdf


This is a good article which re-states much of what has been said here already.

It is instructive to actually measure the current drawn by the various power tools in the workshop:

Kill A Watt™ P4400 Energy Meter - Lee Valley Tools

With this gizmo I have not been able to measure anything approaching the stated HP on the tools I checked so far with the exception of my metal lathe.

One of the more amusing tests was on a Foredom knock off I bought in a local shop: It turned out to be weaker than my Dremel!


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## walowan (Jan 21, 2011)

crquack said:


> This is a good article which re-states much of what has been said here already.
> 
> It is instructive to actually measure the current drawn by the various power tools in the workshop:
> 
> ...




If you are ever running your tools at peak HP you are really overloading them. Normal use will not even come close to peak HP.


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## allthunbs (Jun 22, 2008)

Induction motor, universal motor -- if I remember correctly somewhere on the forum is an item showing the different types of electric motors. How does the type of motor relate to the way their "strength" is rated? I have a 3/4 HP motor on my bandsaw. It's absolutely huge, weighs a ton and looks like it could winch in a lake freighter and not work up a sweat. How does it compare with my 3HP Hitachi M12V router that's less than 1/2 the size?


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## bobj3 (Jan 17, 2006)

Hi

It's sounds like you and I don't have 3HP routers just 1HP to 1 1/2 HP routers :sarcastic::jester: maybe someone should tell Hitachi,Freud,Porter Cable,DeWalt,Triton,Trend,etc. that we want a refund..now that we know Chuck and others are right and they are All wrong,they must know something we don't, now I wonder if my new T4/Colt/DeWalt 1.25hp router is just a 1/4HP router,,...:shout::stop::big_boss:

========



allthunbs said:


> Induction motor, universal motor -- if I remember correctly somewhere on the forum is an item showing the different types of electric motors. How does the type of motor relate to the way their "strength" is rated? I have a 3/4 HP motor on my bandsaw. It's absolutely huge, weighs a ton and looks like it could winch in a lake freighter and not work up a sweat. How does it compare with my 3HP Hitachi M12V router that's less than 1/2 the size?


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## Cherryville Chuck (Sep 28, 2010)

allthunbs said:


> Induction motor, universal motor -- if I remember correctly somewhere on the forum is an item showing the different types of electric motors. How does the type of motor relate to the way their "strength" is rated? I have a 3/4 HP motor on my bandsaw. It's absolutely huge, weighs a ton and looks like it could winch in a lake freighter and not work up a sweat. How does it compare with my 3HP Hitachi M12V router that's less than 1/2 the size?


The following link has the motor descriptions you are referring to as well as an actual HP chart like the other website has.

Electric Motor Basics

I suspect the 3/4 hp motor has a lot more torque than the 3hp router motor has. 

It is too bad manufacturers don't put input power and output power ratings on their products or input power and efficiency. Having the efficiency rating would tell you a bit about how well made the motor is as I would think the quickest way to get more efficiency would be to put better bearings in it.


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## BigJimAK (Mar 13, 2009)

Good link, Charles.. and it's straight-shooting about the amps/horsepower relationship. His ratings for 50%/60%/70% efficient is accurate and probably accurate in a lot of true "industrial" motors (big, heavy, live-forever tanks). Newer motors, even the industrial models run towards the 70% and the lighter-duty industrial induction motors are inching towards 80%. 

In response to the PC Speedmatic 3hp (and any other manufacturers like-rated router) are pure balderdash. I say that and I own (and really like) my Speedmatic.
As for the smaller routers, BJ, yep.. They scale down in HP too... both our Colts are closer to 1/2hp. That said, a horse is pretty strong!! <g>


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## crquack (Oct 10, 2008)

> I have a 3/4 HP motor on my bandsaw. It's absolutely huge, weighs a ton and looks like it could winch in a lake freighter and not work up a sweat. How does it compare with my 3HP Hitachi M12V router that's less than 1/2 the size?


Size is not necessarily related to power. It *may* be related to efficiency which has a lot to do with how the motor is constructed. I suspect the band saw motor is induction, Hitachi is universal. The "3HP" has been covered here several times as well as in the article linked.


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## Cherryville Chuck (Sep 28, 2010)

BigJimAK said:


> Good link, Charles.. and it's straight-shooting about the amps/horseaccurate in a lot of true "industrial" motors (big, heavy, live-forever tanks). Newer motors, even the industrial models run towards the 70% and the lighter-duty industrial induction motors are inching towards 80%.
> 
> power relationship. His ratings for 50%/60%/70% efficient is accurate and probably In response to the PC Speedmatic 3hp (and any other manufacturers like-rated router) are pure balderdash. I say that and I own (and really like) my Speedmatic.
> As for the smaller routers, BJ, yep.. They scale down in HP too... both our Colts are closer to 1/2hp. That said, a horse is pretty strong!! <g>


Thanks Jim,
I agree with you, a good honest horsepower is pretty powerful. 
I think the best idea is just to use a factory hp rating to gauge against other size models and pick something in the range you need. I suspect that there isn't that much difference between your Powermatic and my big Hitachi in what they can rout. I would certainly tell someone now not to bother picking one router over another just because it is supposed to be 1/4hp stronger. I would be more concerned with features and durability.
The Colts you and Bob bought will still do the jobs you bought them for no matter what the actual output is. If it is any consolation, at least it appears that all the manufacturers appear to be lying to us equally.


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## RJM (Apr 11, 2010)

The Warthog said:


> I see the term "Peak HP" on some routers. This term makes me a little suspicious, as I remember that "Peak Music Power" was a misleading figure that used to be used to sell amplifiers when I was young.
> 
> If I want a 2HP router, am I really getting 2HP from a router that says "Peak 2HP?"
> 
> I took grade 10 science a half century ago, and I remember that a HP is about 750 watts, so I'm not sure how a 15 amp (1650 watt) motor can generate 3¼ HP.


Back to the original question which wasn't really answered completely.

Peak HP just means that the Peak Voltage was used to calculate it. Peak voltage for a 120 volt wall socket is about 170 volts (i.e. 120*sqrt(2)= 120*1.414).

Equation for electrical power: P=VI, P = 170v*15a = 2550 peak watts.

There are 746 watts in 1 horse power, so 2550/746 = 3.42 HP but this is the no load HP. Assuming 5% loss in the bearings and brushes (i.e. 95% efficiency) give:

3.42 * .95 = 3.25 HP.

Induction motors turn much slower than universal motors and have higher torques. this makes them much bigger and heavier.

Small, light weight, high speed, low torque universal motors can have the same power rating (HP) as big, heavy, slow, high torque induction motors; however, the useful power of a universal motor is much lower than for an induction motor, so, although they're rated the same, an induction motor will supply greater useful power than a universal motor. Working efficiencies for unversal motors are around 60-70%; for induction motors, they're around 80-90%.


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## crquack (Oct 10, 2008)

If, for a 120V RMS, the current is 15A RMS, then for the peak 170 V the peak current will be also 15A x 1.414 = 21.2A. Thus the peak power (given a constant load) will be 3604W (4.83HP) at 100% efficiency.

3.25 HP output would then represent 67% efficiency which is perhaps more realistic figure than 95% for any motor.

I think it unlikely though that this is what the manufacturers mean when they refer to "peak power".


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## allthunbs (Jun 22, 2008)

So, if I'm to understand all of this correctly, it is quite possible that 3.25 HP (peak) is indeed a valid method of stipulating the power of a motor. In essence it is saying that a 3.25 HP motor can continue to function (albeit for a short time) at 170V. Given that our power fluctuations (here in Québec) routinely hit 170V+ it is comforting to know that my M12V isn't going to blow up in my hands!

Now, I read in...

Electric Motor Basics and 
http://EzineArticles.com/640680

layman's language of universal and induction motors compared. Everything that has been said in this thread seems to apply only to universal motors. 

I have several induction motors in my shop -- bandsaw, tablesaw etc. how do their ratings compare to their labels? Do only induction motors have NEMA ratings? 

How is it that induction motors are stuck at 1750 rpm and universal motors can easily hit 30,000 rpm and more?

I'm trying to broaden the scope of this a bit so I can put it into a summary for myself. It helps when I write it out.

Thanks all for the discussion and the contributions.


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## crquack (Oct 10, 2008)

> So, if I'm to understand all of this correctly, it is quite possible that 3.25 HP (peak) is indeed a valid method of stipulating the power of a motor. In essence it is saying that a 3.25 HP motor can continue to function (albeit for a short time) at 170V.


Not even remotely IMHO. Your motor functions at 170V 120-times a second (60 Hz alternating current, 60-times +170V, 60-times -170V). 120-times a second it sees zero voltage (and current). The effective power, however, (i.e. the power that would be delivered by a direct current of the same voltage) is related to root-mean-square voltage which is 120V, give or take a few volts in Quebec


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## BigJimAK (Mar 13, 2009)

+1 on "Not even remotely"...

CR.. This is way too deep but even if you're delving down into the difference between peak voltage and peak current, they don't occur at the same time (power factor) due to the inductance in the coils. 

It's only 3.25hp through the "Miracle of Modern Marketing". They're not *totally* lieing but it's so deceptive that it should be banned. The sad truth is that if any one company acted responsibly and advertised their "3-1/2hp" router as 1 or 1-1/2hp while everyone else claimed 3-1/2hp they wouldn't sell.


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## allthunbs (Jun 22, 2008)

crquack said:


> Not even remotely IMHO. Your motor functions at 170V 120-times a second (60 Hz alternating current, 60-times +170V, 60-times -170V). 120-times a second it sees zero voltage (and current). The effective power, however, (i.e. the power that would be delivered by a direct current of the same voltage) is related to root-mean-square voltage which is 120V, give or take a few volts in Quebec


Ok, roll it back here. I have a fundamental understanding of Ohm's law. Well that is to say that I can work out watts = voltage * amperage. When I say that Quebec Hydro delivers 170V periodically, I'm referring to something akin to a power surge where we get an overvoltage condition. I don't know about where you are but we are guaranteed power - not power of a specific voltage or current level. That said, where does "root-mean-square" come into it. I can understand that ideal voltage is delivered akin to a sine wave as electrons get pushed back and forth across the wire. (Semiconductor 101 - square voltage rise and drop) Does that mean that if you "average" each wave in a sine wave you come out with "root mean square?"

Sorry to belabour this guys but I've got a thick skull and things don't go in easily and I really need to understand this.


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## Cassandra (Mar 15, 2006)

Hi Jim:

Okay, the peak rating isn't of much technological validity. However, isn't the real problem that there isn't _one_ truly good definition of "peak power" that all manufacturers use in stating the peak power? After all, if there was _one_ definition that all manufacturers used then consumers could compare routers with. For example, one definition would mean that a Ryobi 3-1/4 HP peak power router would have the same power rating as a Porter Cable 3-1/4 HP peak power router, and a Bosch 3-1/4 HP peak power, and . . . We consumers need a specifically defined rating, with which to compare router powers. 

This situation happened in the audio electronics market decades ago. That industry set to the task of defining standard tests for measuring performance. The power tool industry needs to do the same. 

Hey, power tool manufacturers: we consumers need and want a standard test methodology by which all the tools of one class (e.g. routers) can be rated with _one_ industry-accepted rating system.

Cassandra


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## Cassandra (Mar 15, 2006)

Hi Ron:

Your question addresses a basic electrical engineering concept. Hopefully, I can clarify the matter.

Assumption: clean power (Don't you just hate assumptions?)

With clean power, the voltage delivered to the wall outlet by the power supplier is a sine wave, with a *peak* voltage of about 170 Volts. So, the voltage swings between +170 Volts and -170 Volts. 

Now, peak voltage doesn't really tell us how much work that that voltage can do. When the voltage is near zero (120 times per second), the voltage cannot do much work. So, do we use the peak voltage? Well, ah, no. The sine wave is at the peak voltage very briefly twice during each cycle. So, we need some way to measure the voltage to determine the capacity of that voltage to do work. 

Also, if our waveform was a square wave, oscillating between +170 Volts and -170 Volts, it would have a greater capacity to do work than a sine wave. We need some way to compare the capacity to do work for different waveforms.

Scientists (researchers and engineers) determined a mathematical formula to determine the work capacity of different waveforms. That formula is the Root Mean Square method, or RMS. 

In its true form, RMS is a integration equation (Calculus.) (Sorry, I am not up to entering here the mathematical formula in graphical form. Please see http://en.wikipedia.org/wiki/Root_mean_square.) To determine the RMS value mathematically, one takes the integral of the square of the waveform (voltage in our discussion here) and then takes the square root of that integral. This can be quite an involved process, especially when the wave is complex.

For a sine wave, the RMS value equals the peak value over the square root of 2.

For DC and square waveforms, the RMS value equals the peak value. 

For other waveforms, one needs to do the Calculus (yech!!!!) (Can one tell that I'm not keen on this?)

The value of the RMS rating is that one can compare the effective value of one waveform (e.g sine wave) to that of another completely different waveform (e.g. triangle wave.) The RMS methodology allows us to generate an "apple" value for each waveform and thereby avoid comparing apples to oranges.

Cassandra


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## allthunbs (Jun 22, 2008)

Cassandra said:


> Okay, the peak rating isn't of much technological validity. However, isn't the real problem that there isn't _one_ truly good definition of "peak power" that all manufacturers use in stating the peak power?


Hold on a minute. Are you telling me that everything that (I think) I've learned to this point is techno-babble and of questionable validity?



> After all, if there was _one_ definition that all manufacturers used then consumers could compare routers with. For example, one definition would mean that a Ryobi 3-1/4 HP peak power router would have the same power rating as a Porter Cable 3-1/4 HP peak power router, and a Bosch 3-1/4 HP peak power, and . . . We consumers need a specifically defined rating, with which to compare router powers.


That's what I thought I was learning about. Look, there's one electron that flows in a wire. Put 10^16 electrons on a wire and you have a Couloumb. Put some force behind the Coulomb and push them down the wire like beads across a string and you have a volt. Push 1 coulomb hard and fast enough past a given point in one second and you have 1 ampere. Put a detour in front of them and you have a resistor. Put a hurdle and you have a capacitor. Put up a one-way street and you have a diode. Push all of the electrons one way until they get to the end then push them all back again and you have alternating current.

This is the simplistic level that my brain functions on. If I took those electrons and pushed them through a coil of wire to create a magnetic field, I could create a motor. The characteristics of the motor would be dictated by how many turns of the wire, how big the magnetic field, how big is the wire I'm connecting to and, how hard the electrons are being pushed. Surely engineers can't turn this into quantum physics ;-)



> This situation happened in the audio electronics market decades ago. That industry set to the task of defining standard tests for measuring performance. The power tool industry needs to do the same.


So, what forced the audio engineers to find common ground? We should do the same!



> Hey, power tool manufacturers: we consumers need and want a standard test methodology by which all the tools of one class (e.g. routers) can be rated with _one_ industry-accepted rating system.


My vote too!

My head hurts


----------



## allthunbs (Jun 22, 2008)

Lovely. Well done. Very nicely put. 

Now let's go back to the tool motor descriptions. The wattage/horsepower rating should then be at the RMS of a voltage value commonly available to all machines. So, in order to stipulate a 3.5 HP motor we also have to stipulate at what voltage (or standardize the terminology to assure that everyone is talking about 120V RMS) when they say their router is 3.5 HP? Is it possible that is what is being done now? Is it possible that we just don't know their assumptions? But, then if I were a router manufacturer and I stipulated that my motor generated 3.5 HP but I used cheap elliptical bearings that swallowed 1/2 the output of the motor, how would that need to be documented? Do we need to use only Brake HP ratings as opposed to Peak HP ratings?

Fora are fantastic. What other medium would allow so many minds to transfer a concept so proficiently and with so many different contributions. I've known more than a few University Professors in my time and none could have done this any better that you guys (and gals) did. (sorry Cassandra, generic terminology not sexist) 

Thank you all! 

Now, what is "Electro Motive Force" as in a radio wave is "EMF"? I assume (I hate assumptions) that it is like light but not of the visible spectrum? But how do I convert electrons to photons without a light bulb? A radio antennae doesn't glow. When I was studying for my HAM licence I got stuck at this and I've been trying for more than 50 years to get past it.

Ron



Cassandra said:


> Hi Ron:
> 
> Your question addresses a basic electrical engineering concept. Hopefully, I can clarify the matter.
> 
> ...


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## harrysin (Jan 15, 2007)

Now, what is "Electro Motive Force" as in a radio wave is "EMF"?


I know that it's a long time ago but in my school days EMF was defined as "the electrical pressure which causes electricity to flow in a CLOSED circuit. The practical unit of EMF being the VOLT, which is the EMF required to cause 1amp to flow through a resistance of 1ohm.
I've never heard of EMF being referred to when discussing radio waves but ERP, effective radiated power, certainly.


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## crquack (Oct 10, 2008)

> A radio antennae doesn't glow


Mine did...I stuck to the legal limit after that.
As for the rest of it - what Cassandra said!


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## allthunbs (Jun 22, 2008)

crquack said:


> Mine did...I stuck to the legal limit after that.
> As for the rest of it - what Cassandra said!


I couldn't afford a transmitter so I tried to make one from scraps. I overfed the power tube and it glowed purple, almost iridescent green and bright red before I chickened out and pulled the plug. I could never figure out what I did wrong. I think somehow I'd managed to mix up common and ground. That's the only thing I can figure. Ain't it too bad that youth is wasted on the young. Today, I'd get a real hoot out of that experience and look to do it again.


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## Cherryville Chuck (Sep 28, 2010)

I totally agree with Cassandra about a standardized method of measuring power output, and I stress the word output. I am not sure that the tool industry would want that to happen as it might put a few manufacturers out of business. Maybe someone in the States could redirect that Congressman that wants to have all new table saws built with a saw-stop.


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## bobj3 (Jan 17, 2006)

Hi

Just my 2 cents

I'm going to take the manufacturers word for it, when I pay for 3 1/4HP that's what I'm getting and not all the mambo jumbo in this thread.. 
http://www.youtube.com/watch?v=PKpQRjj_WbU&NR=1&feature=fvwp

===========


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## Cassandra (Mar 15, 2006)

bobj3 said:


> Hi
> 
> Just my 2 cents
> 
> ...


Actually, I don't take the manufacturers' words for it! I take the word of fellow woodworkers (like all our good buddies here) and the reviews in the magazines and on the web. At least one can find reviews where they compare routers on the same basis -- not on the whims of the manufacturers.

Cassandra


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## Cassandra (Mar 15, 2006)

Cherryville Chuck said:


> I totally agree with Cassandra about a standardized method of measuring power output, and I stress the word output.


Thanks for being agreeable!

You made a very good point! There should be a standard test, used by all tool manufacturers, measuring the power that the tool puts onto the bit, blade or whatever. Not the power taken from the receptacle. 

Cassandra


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## allthunbs (Jun 22, 2008)

Cassandra said:


> Actually, I don't take the manufacturers' words for it! I take the word of fellow woodworkers (like all our good buddies here) and the reviews in the magazines and on the web. At least one can find reviews where they compare routers on the same basis -- not on the whims of the manufacturers.
> 
> Cassandra


Hi Cassandra:

Examine some of the information I posted on planers. One "publication" evaluated 11 functionally identical planers, all with the same problem. I wonder who "won?"

Of all of the web sites, only Matthias Wendel clearly and correctly defines the problem with the "portable" benchtop planer. I'm sorry that I don't share your optimism when it comes to magazines, books, TV programs etc.

However I do concur with your opinion of fellow forum members. The members of this forum and similar fora on the net, provide far more accurate information than any book, TV star or web site. I have long held the opinion that if you want a router expert, this is the only place to find one. I've even seen dangerous practices on TV programs. So much for the "experts."

It is common for users to know more about a product than the manufacturers. But, rarely do manufacturers actually tap into that resource.


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## allthunbs (Jun 22, 2008)

Cassandra said:


> Thanks for being agreeable!
> 
> You made a very good point! There should be a standard test, used by all tool manufacturers, measuring the power that the tool puts onto the bit, blade or whatever. Not the power taken from the receptacle.
> 
> Cassandra


Ok, what should be in that test?


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## Cassandra (Mar 15, 2006)

allthunbs said:


> Ok, what should be in that test?


Oh, I don't know. Maybe something along the line (for routers):

Maximum Torque at 16000 RPM, 120 Vac input, sustained for a minimum of 30 seconds
Maximum Torque at 18000 RPM, 120 Vac Input, sustained for a minimum of 30 seconds
Maximum Torque at 20000 RPM, 120 Vac Input, sustained for a minimum of 30 seconds
. . .
Maximum Torque at 25000 RPM, 120 Vac Input, sustained for a minimum of 30 seconds

Maximum continuous torque at 25000 RPM, 120 Vac Input, sustained for a minimum of 30 minutes operation at that torque

*Hey, Jim:* What are your thoughts on this issue?

Cassandra


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## bobj3 (Jan 17, 2006)

Hi Cassandra

Well when the good buddies here put a router out one with their name it, I will stick with guys that do and the 1000's and 1000's of people behind them..must be something behind it, so many put one out..and call it 3 1/4 HP at 15 amp's. to 20 amp's.

Heavy Duty
Speed Control
20 Amp.
#9410 • $35.95

http://www.mlcswoodworking.com/shopsite_sc/store/html/smarthtml/pages/speed_control.html

==========
=====



Cassandra said:


> Actually, I don't take the manufacturers' words for it! I take the word of fellow woodworkers (like all our good buddies here) and the reviews in the magazines and on the web. At least one can find reviews where they compare routers on the same basis -- not on the whims of the manufacturers.
> 
> Cassandra


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## crquack (Oct 10, 2008)

> Actually, I don't take the manufacturers' words for it! I take the word of fellow woodworkers (like all our good buddies here) and the reviews in the magazines and on the web. At least one can find reviews where they compare routers on the same basis -- not on the whims of the manufacturers.


+1
Also common sense and understanding basic science helps.


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## Ralph Barker (Dec 15, 2008)

To me, the HP ratings claimed by router manufacturers is completely meaningless, except in a relative sense - that is, a 3 1/4 HP model will have more power than a 2 1/4 HP model, etc. This is especially true if one considers a typical 3HP table saw drawing 14 amps on a 240v circuit. That would be 28 amps on 120v. Would everyone who runs their routers on 15 and 20 amp circuits please raise your hands? 

I like the idea of torque ratings better. Cordless drill manufacturers are starting to use inch-pound torque ratings, and I think that makes more sense.


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## RJM (Apr 11, 2010)

A couple of things I dug up.

1. I read that motor utilization voltages are based on multiples of 115±10% (Cowern Papers http://www.baldor.com/pdf/literature/PR2525.pdf, p53 [acrobat p59])

2. The current rating (e.g. 15A for a "3.25 HP" router) must be the maximum current drawn under normal operating conditions. As a result, it includes all losses (i.e. accounts for efficiency) and also something called "reactive power". This is the power used to create the magnetic fields in a motor winding but is not consumed to do work. It get's returned to the power company each time the current alternates; however, since it flows in the windings, they must be designed to handle the resulting heating from the current. The bottom line is that effects from motor power factor and efficiency are included in the rated amperes of the motor (page 80 of same reference as above - note that page numbers are the printed numbers on each page, not the acrobat page number, which is 6 pages higher). This number is on the motor plate along with the voltage rating (which is for supply voltage - i.e. multiples of 120). 

Taking these 2 bits of information into account, along with what I believe is meant by peak horsepower on something like a router (i.e. a power tool with a universal motor):

115V(rms)*1.414~163V(peak)

163V(peak)*15A(max)=2445W(peak)

2445Wpeak/746W/HP=3.27 HP(peak)

I believe this is what the manufacturers are doing. They round to the nearest 1/4 HP because it's more meaningful to the average person to advertise 3-1/4 HP instead of 3-9/32 HP. Of course, as soon as the first company does this, everyone else must follow, or get left behind.

Note that this takes into account the voltage of the motor and the maximum current rating, so a motor made for some place that uses a different voltage will also have a different current rating.

I also went and looked at the 3HP induction motor on my planer. Its plate says "OUTPUT 3.0 HP". It's also rated at 230/240 V and 18 amps. Working with these values, you get the following:

230V-10%= 207V

207V*18A(max)=3726W

3726W/746W/HP=5.0 HP

Now take into account motor efficiency and power factor. Assume the following:

Efficiency = 80% and PF = 75% (typical for induction motors)

Now, 5.0 HP*.80*.75 =3.0 HP

So although consumer product manufacturers use total input power (including non-useful reactive power) along with peak AC voltage to artificially boost the advertised HP of a small power tool, it seems that commercial motor manufacturers must use output power on their motor plates. By the way, I bet if you look at your drill, router, or circular saw motor tag, you will only find voltage and current ratings (no HP on these tags).

Going back to the 3.25 HP universal motor, assume a power factor of 75% and an efficiency of 70%. I read somewhere that universal motors are less efficient than induction motors but I can't find any data on them. I did find a paper about developing a high efficiency universal motor of 77%, so I think the 70% I assumed here is about right.

120V(rms)*15A(max)=1800W(max input)

1800W*.70*.75=945W(output)

945W/746W/HP=1.27 HP (output)

So, our 3.25 HP routers are actually putting out about 1-1/4 HP. The good thing is that everyone rates them the same way, so there is a quasi standard and you can compare one router to another by the HP rating since most universal motors all behave the same way.

One more thing, since brake horsepower measures output power, there's no way that's what is meant by the HP rating of a router (i.e. universal motor). Also, while induction motors can put out quite a bit more power than they're rated for, the behavior of a universal is different. The maximum power for a typical universal motor occurs at about 60% to 70% the rated maximum speed. Since torque and power drop off with increased speed, this cannot be the explanation for peak HP of these motors either.

Note that maximum torque for a universal motor occurs at shaft lock (i.e. speed =0). This is also where maximum current occurs and is much higher than the rated current (that's why the motor burns up).


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## BigJimAK (Mar 13, 2009)

Cassandra said:


> Oh, I don't know. Maybe something along the line (for routers):
> 
> Maximum Torque at 16000 RPM, 120 Vac input, sustained for a minimum of 30 seconds
> Maximum Torque at 18000 RPM, 120 Vac Input, sustained for a minimum of 30 seconds
> ...


I like where you're going here with this Cassandra. My tweak would be to try to be more real-world for the 30 second test mine would be a series of 30 second tests with, say, 30 seconds running without load between to permit cooling and simulate repeated cuts. 

My thinking here is for it to avoid someone loading it so heavily it'll take 30 minutes to cool.


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## allthunbs (Jun 22, 2008)

Hi RJM60:

Are you saying that you're content with the status quo? Do you consider 3.25 HP on 120V line to be a realistic evaluation of a universal motor then?



RJM60 said:


> A couple of things I dug up.


Your explanation is valid, as far as I can figure -- I'll await the comments of the jury. In which case, can we turn your explanation into something more palatable for the non-electric router user? I'm just now managing to get my head around RMS.

Thanks for taking the time and trouble to prepare your comments.


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## allthunbs (Jun 22, 2008)

Cassandra said:


> Oh, I don't know. Maybe something along the line (for routers):
> 
> Maximum Torque ...


Ok, torque is relative on a universal motor -- isn't it? The more you demand of the motor the more it responds and the result is heat? How are you going to consider the heat factor?



> BigJim: My thinking here is for it to avoid someone loading it so heavily it'll take 30 minutes to cool.


Remember that the purpose of 3.25HP is to provide some sort of number that illiterates like me can easily sink their thick skulls into and say "this router is better than that one because it has more horsepower." It is indeed oversimplification but could it be the least of evils? Could the EU method of watts be more valid? 

Next, 120VAC input is a median voltage. If you do your evaluation on 120V (RMS?) and manufacturers rebuild their motors to that test, how will they (the motors) handle overvoltage and greyouts?

I classify routers based on horsepower. It is an indication to me of what kind of work a router can do and what kind of performance I can expect from it. I have to accept Ralph's comment that it is all relative.

That said, this discussion has real value in the real world. The method of evaluation of universal motors is indeed overdue.


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## allthunbs (Jun 22, 2008)

I went digging and came up with this explanation of the different types of motors. Perhaps other non-electric types will find it useful...

http://www.howeverythingworks.org/supplements/electric_motors.pdf


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## allthunbs (Jun 22, 2008)

Actually the "good buddies" would have nothing to do with it. Standards are now set by committees of interested users and producers. Since this forum represents interested users in quantity and quality it speaks with a loud voice. This discussion, should it arrive at some sort of conclusion, will be well known to those standards bodies.



bobj3 said:


> Hi Cassandra
> Well when the good buddies here put a router out one with their name it, I will stick with guys that do and the 1000's and 1000's of people behind them..must be something behind it, so many put one out..and call it 3 1/4 HP at 15 amp's. to 20 amp's.
> 
> Heavy Duty
> ...


Actually, there would only be a few "people" behind those "standards" since few people actually understand them. I would think much of the current "standards" are just plain arbitrary assignment of "rough" numbers. If there were actually a standard it would be prefaced by "ISA" or some other standard. Do not confuse standard with "UL" or "CSA." Those standards only state that "they don't think the product will burn your house down."

BTW, "heavy duty speed control 20 Amp." may, or may not, work with any specific motor. I have learned that there are 5 different types of motors and this speed control only works with one type. 

That said, the status quo must also be considered no matter how it is delivered.


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## Ralph Barker (Dec 15, 2008)

Robert - I'm pretty sure that you are correct in how the manufacturers are calculating HP. I've seen that mentioned before, but couldn't remember the formula. 

Since they all use the same calculation method, I suppose it satisfies the purchaser's need to judge relative power, even if it's a bogus measure of true HP. Maybe. 

Where the calculated HP may fall down is with comparisons of similar tools from different manufacturers. Personally, I have more trust in the relative measure regarding tools intended for industrial use (e.g. the PC 7518), but less trust with respect to tools intended for home/consumer use (e.g. Ryobi tools). 

What the calculated HP rating doesn't address is efficiency and durability. That is, does Tool X deliver the power needed for the intended task, and does it stand up under continued use? Since there aren't any industry standards for tool testing, magazine reviews tend to be all over the place in terms of reliability. Thus, we're back to relying on testimonials from users whose judgement we trust.


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## harrysin (Jan 15, 2007)

I'm sure that any routing beginners reading this thread must be totally miffed.
I, and I think Bj have been using routers extensively for over 35 years and as has been mentioned, it's only necessary to know the rated horse power to use as a comparison, 2 hp being a more powerful tool than a 1hp. I don't think that it matters one iota whether these figures are accurate or not. Anyone reading through my past threads will see that I have always advocated a "big" router, even for the first time buyer because once one has grasped the finer points of routing, the sky will be the limit of what that "big" router can achieve, unlike starting with a small 1/4" machine. Until not all that long ago, air-conditioners in Australia were rated by horse power which made comparisons simple, but now we use the more accurate BTU's but laypeople that I've spoken to get confused with the large figures compared to single digits. I really don't see the necessity to find a new unit for routers that could potentially cause similar confusion.


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## bobj3 (Jan 17, 2006)

Hi

Now I will 2nd Harry's post on this thread..the rest of the posted items are just so much hog wash..hill of beans..

=====



harrysin said:


> I'm sure that any routing beginners reading this thread must be totally miffed.
> I, and I think Bj have been using routers extensively for over 35 years and as has been mentioned, it's only necessary to know the rated horse power to use as a comparison, 2 hp being a more powerful tool than a 1hp. I don't think that it matters one iota whether these figures are accurate or not. Anyone reading through my past threads will see that I have always advocated a "big" router, even for the first time buyer because once one has grasped the finer points of routing, the sky will be the limit of what that "big" router can achieve, unlike starting with a small 1/4" machine. Until not all that long ago, air-conditioners in Australia were rated by horse power which made comparisons simple, but now we use the more accurate BTU's but laypeople that I've spoken to get confused with the large figures compared to single digits. I really don't see the necessity to find a new unit for routers that could potentially cause similar confusion.


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## Phil P (Jul 25, 2010)

Thanks for that, Bob......

Seen from a European perspective all this seems a bit odd. In the EU router manufacturers generally quote rated input and rated output in watts. By that measure a deWalt DW625EK (1/2in) plunge router has an input rating of 2000w and an output of 1400w whilst its' bigger brother the DW626 is rated at 2300w/1560w respectively. Interestingly the DW618 equivalent over here (the snappily named D26204K) is rated at 900w/620w (input/output) whilst the older DW615 (successor to the mighty Elu MOF96) shows at 900w/590w, so maybe there's something in modern motors being more efficient.

Any of our electrically savvy contributors care to explain what these figures mean in real terms?

Phil


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## allthunbs (Jun 22, 2008)

harrysin said:


> I'm sure that any routing beginners reading this thread must be totally miffed.


Actually I would think that anyone not interested in this thread just wouldn't read it. It's a bunch of people having fun with the absurdity of non-standardized measuring systems. If a newbie wishes to read it and ask questions and learn, what's the harm in that? Are we actually hurting someone by discussing something of interest to us?



> I, and I think Bj have been using routers extensively for over 35 years and as has been mentioned, it's only necessary to know the rated horse power to use as a comparison, 2 hp being a more powerful tool than a 1hp. I don't think that it matters one iota whether these figures are accurate or not.


Isn't that for the reader to decide? Perhaps a simple discussion could lead to a more meaningful value being applied to a router. Perhaps that value could compare Brand X 3.5 HP to Brand Y 3.5 HP and provide meaningful information as to which is better designed and/or built?



> Anyone reading through my past threads will see that I have always advocated a "big" router, even for the first time buyer because once one has grasped the finer points of routing, the sky will be the limit of what that "big" router can achieve, unlike starting with a small 1/4" machine.


So, what does that have to do with an effective and valid system of measurement? Is a Ryobi 3.25 HP router "bigger" than a Makita 3.25HP router? How do you know?



> Until not all that long ago, air-conditioners in Australia were rated by horse power which made comparisons simple, but now we use the more accurate BTU's but laypeople that I've spoken to get confused with the large figures compared to single digits.


Yet it is far more simple to use a 6,000 BTU air conditioner to cool a space requiring 6,000 BTUs of cooling.



> I really don't see the necessity to find a new unit for routers that could potentially cause similar confusion.


For the same reason that you're pushing the use of metric. Metric is a reasonable system of measurement. Why can't we have a world-wide standard for routers? In North America we use HP which means little. In Europe they use watts which means a little bit more but is still subject to prevarication or "interpretation." I'm not sure what they use in the orient but I'll bet it's no more reliable than HP. There is no method of allowing the comparison of one router to another. In this day and age of managed information and wordsmiths constantly putting a spin on something we, the buying public, are fed up with the mistruths -- they're not lies but on a balance of truth they would be. It would be nice to have real meaningful information for once.

Ron


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## Mark (Aug 4, 2004)

Lets keep it friendly in here guys , remember to respect each others opinions.


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## Cassandra (Mar 15, 2006)

BigJimAK said:


> I like where you're going here with this Cassandra. My tweak would be to try to be more real-world for the 30 second test mine would be a series of 30 second tests with, say, 30 seconds running without load between to permit cooling and simulate repeated cuts.
> 
> My thinking here is for it to avoid someone loading it so heavily it'll take 30 minutes to cool.


Thanks, Jim! Maybe all of us can come to some consensus on how to rate the tools and then put it to the manufacturers to comply with the users' expectations.

I can dream, can't I?

Cassandra


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## TwoSkies57 (Feb 23, 2009)

I've actually found most of this thread interesting! I do appreciate the time and expertise many have contributed to it, if just to make their point and to further the discussion.


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## Cherryville Chuck (Sep 28, 2010)

Phil P said:


> Thanks for that, Bob......
> 
> Seen from a European perspective all this seems a bit odd. In the EU router manufacturers generally quote rated input and rated output in watts. By that measure a deWalt DW625EK (1/2in) plunge router has an input rating of 2000w and an output of 1400w whilst its' bigger brother the DW626 is rated at 2300w/1560w respectively. Interestingly the DW618 equivalent over here (the snappily named D26204K) is rated at 900w/620w (input/output) whilst the older DW615 (successor to the mighty Elu MOF96) shows at 900w/590w, so maybe there's something in modern motors being more efficient.
> 
> ...


I would love to see that system applied over here. The input power power tells you how much the power company is charging you to use it, the output power tells you how much work it will actually do, and the ratio of the latter to the former is how efficient it is with the power it receives. The math on those mentioned puts them in the 65.5% to 70% range, a difference of only about 6 1/2%. I think those figures, a manufacturers reputation, and the limit to which they are willing to warranty the tool would give a prospective buyer some useful information to make a decision with.


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## RJM (Apr 11, 2010)

allthunbs said:


> Hi RJM60:
> 
> Are you saying that you're content with the status quo? Do you consider 3.25 HP on 120V line to be a realistic evaluation of a universal motor then?
> 
> ...


Yes, I'm okay with the status quo. The main difference is that the manufacturers are calculating total input power instead of net output power. As long as everyone does it the same way, it's probably still a pretty good comparison. Also, there are so many other things to compare when it comes to power tools, I don't think the small differences in useable power between manufacturers will amount to much. A 3.25 HP router is still 50%+ more powerful than a 2HP, etc.

****************************************
Here's a copy of an email I received from a pump design engineer:

Date: Mon, 11 Apr 2011 15:47:35 -0700
Subject: Re: Universal motor peak HP

Hi Robert, retail takes advantage of customer's lack of knowledge. Usually HP over rating is not as bad as this one. Usually they do the calculation at RMS and assume 100% efficiency. I think you have it right in that they used peak voltage and also assumed 100% eff. There is no way they could come up with that HP otherwise. The retail pump industry also does this but in the opposite direction. They will label a residential water pump at 1/2 Hp but it will have a service factor of 1.6 so it is actually 3/4 Hp. That way one manufacturer can advertise that their 1/2 Hp pump provides the same performance of the competitors 3/4 Hp model. Regards, Joe


==============
On Sun, Apr 10, 2011 at 11:17 PM, Robert wrote:
Found you're website (http:*[FONT=Arial,Arial][FONT=Arial,Arial]//**[/FONT]*[/FONT]www.PumpEd101.com ) and thought you might be able to help with this question.

The question of peak HP advertised on power tools like routers and shop vac’s came up and I was wondering if you could shed some light on what manufactures are basing claims of 3.25 peak HP on for a router rated at 120V supply and 15A max current.

The only thing I can come up with (after a couple days of research) is that they are basing it on peak voltage (i.e. 115*1.414) rather than an RMS value (115, or 120) and using the max current rating which includes losses and reactance (i.e. max apparent power).

Thanks,
Robert
​


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## RJM (Apr 11, 2010)

Cherryville Chuck said:


> I would love to see that system applied over here. The input power power tells you how much the power company is charging you to use it, the output power tells you how much work it will actually do, and the ratio of the latter to the former is how efficient it is with the power it receives. The math on those mentioned puts them in the 65.5% to 70% range, a difference of only about 6 1/2%. I think those figures, a manufacturers reputation, and the limit to which they are willing to warranty the tool would give a prospective buyer some useful information to make a decision with.


I don't know .. I'm kind of a HP guy ... "more power, arh, arh".


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## crquack (Oct 10, 2008)

> Interestingly the DW618 equivalent over here (the snappily named D26204K) is rated at 900w/620w (input/output)


Compare with the North American DW618 advertised at 2-1/4 HP "maximum motor power" and 12A (???). The EU figures seem much more realistic and honest, although it still isn't clear how these figures are measured (at what load).

It is interesting because the Europeans have the capacity to produce much more powerful tools given the mains voltage of 220-240V (at 240V and 15A that is 3600W or 4.8 HP). At least in UK I recall household circuits wired for 15A.


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## BigJimAK (Mar 13, 2009)

Phil P said:


> Thanks for that, Bob......
> 
> Seen from a European perspective all this seems a bit odd. In the EU router manufacturers generally quote rated input and rated output in watts. By that measure a deWalt DW625EK (1/2in) plunge router has an input rating of 2000w and an output of 1400w whilst its' bigger brother the DW626 is rated at 2300w/1560w respectively. Interestingly the DW618 equivalent over here (the snappily named D26204K) is rated at 900w/620w (input/output) whilst the older DW615 (successor to the mighty Elu MOF96) shows at 900w/590w, so maybe there's something in modern motors being more efficient.
> 
> ...


Phil,

The input / output rating in watts is a truer rating for power, as long as the manufacturer plays fair and uses an output value based on a realistic test.

More to the point, a Horsepower is 746 watts watts, so the DW626 is 1560W / (746 watts/HP) = 2hp and a hair. <g>

I'm with Harry in that router horsepower ratings have little true meaning... and (from what is commonly available in the US) I believe that Amps provides a better comparison than HP... at least its tied to something more real.

FWIW, I suspect that the 15 Amp Bosch MRC23EVSK, rated at 2.3hp, would test comparable to other 15Amp routers claiming 3 or 3-1/4hp. Whether you love or hate Bosch, they are a reputable manufacturer of tools and I do not believe that their new router is really only 70% as efficient as their competition.

Whether you're talking ShopVacs or routers, I for one use Amps as a better measure of power. Just as with small air compressors I use air delivered at a certain pressure over "peak horsepower".

I have a 60 gallon Ingersoll Rand compressor with a 5hp Induction motor that delivers 14.7 CFM at 175psi. It also draws 20+A at 240VAC. 

You will see other companies with "5hp" compressors that run on 120V, 15A and guess what... they deliver *much* less air at lower pressure... a good measure of the "work" performed.


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## bobj3 (Jan 17, 2006)

HI Jim

Just to add some more wood to the fire 

"I have a 60 gallon Ingersoll Rand compressor with a 5hp Induction motor that delivers 14. CFM at 175psi. It also draws 20+A at 240VAC. "

I have one also and it pulls 35 to 40 amps. 26.5 CFM,240V ,it's on a 50 amp. breaker, just like my mig welder...



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BigJimAK said:


> Phil,
> 
> The input / output rating in watts is a truer rating for power, as long as the manufacturer plays fair and uses an output value based on a realistic test.
> 
> ...


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## BigJimAK (Mar 13, 2009)

bobj3 said:


> HI Jim
> 
> Just to add some more wood to the fire
> 
> ...


LMAO, BJ.. What can I say.. yours is bigger than mine!!! :haha:

That means you've got more hot air than...  No...no...I can't go there..  


:jester:


I was *wondering* where you got all that air for your pneumatic router!!


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## harrysin (Jan 15, 2007)

"Actually I would think that anyone not interested in this thread just wouldn't read it. It's a bunch of people having fun with the absurdity of non-standardized measuring systems. If a newbie wishes to read it and ask questions and learn, what's the harm in that? Are we actually hurting someone by discussing something of interest to us?"

My point was that beginners look to this forum as an aid to deciding what router to buy, particularly regarding horse power, so any thread that mentions horse power would be relevant to such members, hence my remark that they would be miffed. Had this thread been in the lobby, that would have been different, but it was in "general routing". Why this remark drew the response that it did from you I can't imagine.


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## bobj3 (Jan 17, 2006)

Hi Jim

For the routers,floor jacks,bottle jacks,bench press,sand blaster cabinet,spray jobs, drills motors,hold down devices,nailer,grinders, etc. I use a lot of air tools..I think I have more air lines than drop cords in the shop...hard and soft ones..


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BigJimAK said:


> LMAO, BJ.. What can I say.. yours is bigger than mine!!! :haha:
> 
> That means you've got more hot air than...  No...no...I can't go there..
> 
> ...


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## Ralph Barker (Dec 15, 2008)

harrysin said:


> My point was that beginners look to this forum as an aid to deciding what router to buy, particularly regarding horse power, so any thread that mentions horse power would be relevant to such members, hence my remark that they would be miffed. Had this thread been in the lobby, that would have been different, but it was in "general routing".


But, isn't it helpful for beginners to recognize that the HP ratings are useful only in a relative sense, Harry? And, that the relationship may not be accurate across brands? (That is, one manufacturer's tools may be more efficient than those of another manufacturer.)

In photography, a similar "issue" exists with respect to electronic flash units designed for studio use. Most manufacturers state ratings in terms of input watts (power consumption), but say nothing about output. But, there can be significant differences in actual light output between units having the same power consumption. 

In the '50s, when I started using routers, a certain amount of faith in the manufacturers was probably justified. I'm not sure that is still the case these days. 

On the other hand, I'm reasonably sure that the conversation here isn't going to convince manufacturers to change the rating system they use.


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## allthunbs (Jun 22, 2008)

harrysin said:


> My point was that beginners look to this forum as an aid to deciding what router to buy, particularly regarding horse power, so any thread that mentions horse power would be relevant to such members, hence my remark that they would be miffed. Had this thread been in the lobby, that would have been different, but it was in "general routing". Why this remark drew the response that it did from you I can't imagine.


Then, they will learn a tremendous amount. If I can understand the content of this thread, anybody can.


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## allthunbs (Jun 22, 2008)

Ralph Barker said:


> But, isn't it helpful for beginners to recognize that the HP ratings are useful only in a relative sense, Harry? And, that the relationship may not be accurate across brands? (That is, one manufacturer's tools may be more efficient than those of another manufacturer.)
> 
> On the other hand, I'm reasonably sure that the conversation here isn't going to convince manufacturers to change the rating system they use.


Hi Ralph:

My thinking with this thread is that if we can come to some sort of consensus the standards organizations can be made aware of that consensus. It will then go into their committee for universal motor evaluations and techniques where it will be examined in full over time. Our forum is probably one of the best you can get for such a discussion since we cover the gamut from electrical engineers to craftsmen and everything in between all discussing a common point. 

What we've accomplished to this point is a suggestion that torque be a method of evaluation. We've also heard that watts in and watts out might also be a valid standard of measure. These are all well thought out proposals and standards organizations are constantly on the lookout for "interested parties" to contribute to the discussions.

It's not the manufacturers per se but the lack of a standard. Nothing is going to change manufacturers until they're forced to change. There's nothing better than the status quo. However, standards organizations (ISA, DIN etc.) will quickly pick up on something in the public interest and begin the process of evaluating how a standard could be created. Once a standard becomes available, manufacturers will fall into line. It is in their better interest.


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## harrysin (Jan 15, 2007)

" But, isn't it helpful for beginners to recognize that the HP ratings are useful only in a relative sense"

Certainly Ralph, IF it was stated in non-technical terms rather than AC theory!


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## Ralph Barker (Dec 15, 2008)

harrysin said:


> " But, isn't it helpful for beginners to recognize that the HP ratings are useful only in a relative sense"
> 
> Certainly Ralph, IF it was stated in non-technical terms rather than AC theory!


_All_ of my theories are AC, Harry. Alternating consistency.


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## harrysin (Jan 15, 2007)

Don't sell yourself short Ralph.


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## oldrusty (Mar 31, 2011)

One sure fire way of knowing that the smoke is burning varnish in the motor windings is that it invariably smells slightly sweet and fruity. Having smelt it once you will never forget that distinct smell. Old rusty


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## RJM (Apr 11, 2010)

arjibakoh3 said:


> Just got a note back saying that there isn't much left since they are liquidating. And I should go to the US Factory Outlet page of their site and try for something there..


 
Let us know what happens ....


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## garycurtis (Sep 17, 2007)

My background with power tools was automotive restoration. Sears, along with other companies, used the Developed Horsepower rating for air compressors. (Induction motors) Owners learned to grow very suspicious of power ratings claimed by Sears. Here's why. 

The irony (and maybe a truth pill) is the fact that air compressor output can be measured independent of power input at the motor. PSI and CFM of the pump output. Sears more or less shot themselves in the foot because they sold similarly sized air compressors with either an induction electric motor or a gas engine. And for some strange reason, a 2.5hp Gas compressor would put the out same PSI and CFM as an identical unit with a 4 or 5hp electric motor. Now they were dealing with Induction motors, not Universal motors. But a guy running a compressor for 2 hours typically ran into the same limitation as a guy with a router. The electric motors overheat badly in either. (not nearly as bad as in a router because of the poor fan cooling on a universal motor).

Now here is a bizarre twist of technology that might enter the router world. I own a few Festool tools, including their 1400 router. It looks and feels like a 2 1/4 hp unit, but is rated in Watts. So, who knows how Americans would rate that?

But I also have one of their portable drills. The model (the C-12) drill with a 3-phase, brushless motor. It is essentially an Induction motor running on batteries. 3-phase, to boot. 

I don't understand this too well, but the 3-phase aspect gives it incredible torque. Scary torque. And relatively moderate current draw, so battery charge is extended. And it is light as a feather. And since it has no brushes, they tested one a unit on an automated fixture and were able to drive 1 million screws. They then tore the drill down and found no appreciable wear nor any damage. Less moving parts to wear out.
I wonder how long before Festool releases a brushless router (wired of course). As someone stated, Festool is European- made. They rate their tools in watts. Battery, whether plug in or batter operated.


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## Joesf (Nov 27, 2010)

BigJimAK

I read your response on the HP rating and it is good. I think we can agree that the HP ratings are nonsense for some tools . For instance Bosch advertises their contractor 4100 series table saw as being 4HP. Now we all know what a real 3 or 5 HP table saw looks and preforms like.


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## Mike (Nov 22, 2004)

Perhaps the best idea is to use the power ratings to simply get an idea of the tool's power. Performance varies greatly between different brands and models. Anyone who uses a PC 690 series router will be amazed at the difference in cutting when using a PC 890 series or my weapon of choice the Bosch 1617. Rating for the 690's is 1-1/2 HP; the 890's and the 1617 is 2-1/4 HP. Rather than worry about how accurate the rating is' just know that there is a difference in performance. This will help you in your purchasing decisions.


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## dgcutter (Dec 25, 2012)

I had a new Dewalt drill that smoked. I changed the brushes and no more smoke.


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