# weight to speed?



## sunnybob (Apr 3, 2015)

Any body here know how to decide what speed a certain router bit should be used at? I'm contemplating buying a large diameter 1/2" bit but my makita router does not have speed control.
The manual just gives a vague "match weight to speed" but no specifics.
Any weight / speed charts out there?
I'd prefer actual charts rather than seat of the pants "feel


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## Stick486 (Jan 4, 2013)

here.....

.


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## sunnybob (Apr 3, 2015)

Bad news week.
My router is non adjustable and the bit i wanted is supposed to run at half my speed.
Back to the xmas shopping lists.
Thanks


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## Stick486 (Jan 4, 2013)

if it isn't a soft start put an external speed controller on it...


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## tulowd (Jan 24, 2019)

I put this HF speed control on my woodpecker/porter cable router table:

https://www.harborfreight.com/router-speed-control-43060.html

Best $20 you can spend IMHO.

They also make momentary or maintained $15 foot pedals on off switches that are awesome for drill press etc.

https://www.harborfreight.com/search?q=foot pedal


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## sunnybob (Apr 3, 2015)

I like the idea of a soft start. But I can not find one suitable outside the USA.
Most of my equipment comes from the UK at 230 volts. My makita takes 13 amps, and the only UK controller i can find is 8 amps.

still not good news.


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## harrysin (Jan 15, 2007)

What type of bit are you contemplating? If it's for raised panel doors, go for a vertical bit, it's far safer than a horizontal one spinning at around 15,000 rpm.


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## sunnybob (Apr 3, 2015)

I found a 2 3/4" bottom cleaning bit, and a lock mitre bit, but they are big boys.


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## harrysin (Jan 15, 2007)

sunnybob said:


> I found a 2 3/4" bottom cleaning bit, and a lock mitre bit, but they are big boys.


I bought this 3 3/4" Forstner bit for a one off project and in the drill press at it's lowest speed it scared me. A 2 3/4" router bit spinning at a suitable speed would also scare me and I'm not easily scared but am accident conscious.


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## sunnybob (Apr 3, 2015)

I cant work this out. In the USA, variable speed controllers for up to 15 amp machines are $20 or less.
In the UK, The ONLY controllers that take 15 amps are $70 and more.
The exact same pictures of the 15 amp on the amrican sites are used on the UK sites, but are then only rated for 8 amps.


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## DaninVan (Jan 1, 2012)

Bob; am I missing something? Isn't that basically the same thing considering the UK voltage is double that of N. America? Assuming the motor wattage is the same on both machines?


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## Cherryville Chuck (Sep 28, 2010)

Bob I thought your standard circuit was 230 volt and 7.5 amps. Is that not correct? If I remember the formula correctly then 7.5 amps at 230 volts should equal 1725 watts which is about what that Makita would be running if it was on a 110 volt 15 amp circuit here. All of our routers will run on a standard branch circuit here. Maybe Harry could respond to that. I know he's more knowledgeable on the subject than I am. If I got all that right then that might explain why you can only find an 8 amp controller.


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## sunnybob (Apr 3, 2015)

Well that has stirred the waters a bit. 
UK (and Cyprus) electricity standard power circuit is 230 volts 13 amps wall socket. All power tools are supplied with a 3 pin socket that contains a 13 amp fuse.
I used an online calculator and input 230 volts and 1800 watts and it told me 15 amps. I believed this untill having read this reply. 

It looks like I was misled.

I have just looked out the instruction book that came with the router and it does not state supply requirements, only that it must be fitted as per the data plate on the machine.
The machine itself is buried inside a fully enclosed router table and I am just too busy to take it all apart at the moment.

I've tried looking it up on ebay.co.uk (which is where I bought it) but it appears to no longer be sold in the UK.

Its a makita RP1800 running on 230 volts 50 cycles. If anyone can work that out please let me know.


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## TenGees (Sep 12, 2012)

Dan is right. A similar router running at twice the voltage would require about half the current (amps).


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## sunnybob (Apr 3, 2015)

I cant catch a break here.
just been back to ebay UK, and there are lots of 8 amp speed controllers at very good prices, but they are all rated for 1500 watt.
My router is 1800 watt. How long before the controller burns out on overload?


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## Nickp (Dec 4, 2012)

sunnybob said:


> I cant catch a break here.
> just been back to ebay UK, and there are lots of 8 amp speed controllers at very good prices, but they are all rated for 1500 watt.
> My router is 1800 watt. How long before the controller burns out on overload?



...at 1800W/230V, doesn't that equate to just under 8 amps...?


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## sunnybob (Apr 3, 2015)

Nick, I dont know. I can install (from schematics), repair, and troubleshoot electrics, but I dont have the theory to work things out.
The box states max 1500w, my makita states 1800w, Thats the only maths I can do.


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## harrysin (Jan 15, 2007)

Cherryville Chuck said:


> Bob I thought your standard circuit was 230 volt and 7.5 amps. Is that not correct? If I remember the formula correctly then 7.5 amps at 230 volts should equal 1725 watts which is about what that Makita would be running if it was on a 110 volt 15 amp circuit here. All of our routers will run on a standard branch circuit here. Maybe Harry could respond to that. I know he's more knowledgeable on the subject than I am. If I got all that right then that might explain why you can only find an 8 amp controller.


Yes Charles, that Makita router is rated at 1850 watts and because amps equal watts divided by volts it becomes:
1850 divided by 230 which equals 8 amps. I know that the purists will point out that the formula relates to direct current but it's close enough.


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## Nickp (Dec 4, 2012)

sunnybob said:


> Nick, I dont know. I can install (from schematics), repair, and troubleshoot electrics, but I dont have the theory to work things out.
> The box states max 1500w, my makita states 1800w, Thats the only maths I can do.


Gotcha...I had forgotten that 50Hz draws more current than 60Hz...about 1.2 times the power...

I'm with you...go with the specs on the box for 50Hz machines...


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## harrysin (Jan 15, 2007)

sunnybob said:


> I found a 2 3/4" bottom cleaning bit, and a lock mitre bit, but they are big boys.


I've used the 1 3/4" bottom cleaning bit and the 1 1/4" bowl bits extensively for planing mainly hard wood using the router skis. Using such a large bit that you describe is critical that it is perfectly parallel to the board or lines will be produced. Using skis is very fast so there is little to be gained using HUGE bits.
As for the lock mitre, these two bits cover a big range of wood thicknesses up to a little over 3/4". The small one is 1 1/2" dia. and the larger one 1 3/4".


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## Cherryville Chuck (Sep 28, 2010)

sunnybob said:


> I cant catch a break here.
> just been back to ebay UK, and there are lots of 8 amp speed controllers at very good prices, but they are all rated for 1500 watt.
> My router is 1800 watt. How long before the controller burns out on overload?


It's only pulling that many watts under heavy load and maybe at startup just to get the bit spinning.


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## Cherryville Chuck (Sep 28, 2010)

Nickp said:


> Gotcha...I had forgotten that 50Hz draws more current than 60Hz...about 1.2 times the power...
> 
> I'm with you...go with the specs on the box for 50Hz machines...


I thought it only affected the speed. Changing hertz is how many controllers work these days. I've heard that if you get down too low you can have an issue with torque drop.


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## sunnybob (Apr 3, 2015)

Cherryville Chuck said:


> It's only pulling that many watts under heavy load and maybe at startup just to get the bit spinning.


 But the only time I would use the speed control would be under load with a big cutter, from startup


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## Cherryville Chuck (Sep 28, 2010)

I think we may have a problem Bob in finding anyone with experience using a controller on EU type power. You may have to decide if you want to be the guinea pig. I can tell you from experience that even at recommended speeds listening to one of those very large bits come up to speed is just a bit intimidating.


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## sunnybob (Apr 3, 2015)

Charles, the main problem with me being a guinea pig is that I would have to buy in the UK. That means 3 or maybe 4 weeks before it arrives. then, if it goes wrong, it would cost more money to send it back than it cost in the first place. which would leave me 2 months down the line out of pocket not just for the box but the large bits as well. Thats almost a couple hundred dollars.

I'm going to have to shelve the project untill I can find a definitive answer.


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## Cherryville Chuck (Sep 28, 2010)

Are there any electrical repair shops in the area? They would have a better idea if it would work.


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## Nickp (Dec 4, 2012)

Bob...are there other items that a speed controller could be available for you, for example, a fan or other such device...? Maybe instead of looking for a router controller just a plain ole controller for an 1800W motor...? I dunno...fan, exercise equipment, food blender... just grasping at straws here...

Maybe a call to an electrical supply shop...?


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## DesertRatTom (Jul 3, 2012)

Hi Bob, I notice that in most posts, you give the amps and or wattage, but not the volts. That would clarify the issue somewhat. I think most of the amps or watts are stated for startup. Running takes less unless the bit is large, then the amps will rise because the load is heavier. I think you either need a local electrician or to contact the route maker for their take.


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## Nickp (Dec 4, 2012)

DesertRatTom said:


> Hi Bob, I notice that in most posts, you give the amps and or wattage, but not the volts. That would clarify the issue somewhat. I think most of the amps or watts are stated for startup. Running takes less unless the bit is large, then the amps will rise because the load is heavier. I think you either need a local electrician or to contact the route maker for their take.



Bob did say he was on 230V


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## DaninVan (Jan 1, 2012)

And *50 *Hz...not 60.


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## Biagio (Mar 2, 2013)

@sunnybob,
What you can get is an AC motor controller kit. It may require a very small amount of soldering, which I assume you can manage - there are only a few components (as in 5 or 6).
Locally (also 220/230V country) a 2000W kit costs about 10 Euro (may need an enclosure - small metal box, two grommets, cable in and out). If you want to go big, a 10KWatt kit is around the 30 Euro mark. The kits are based on a diac-triac pair, pretty much like what is built into variable speed machines.
If you feel up to it, you can just get the components, but you might have to fiddle with a mounting board and heat sink.

I made a 1000Watt controller for a small motor to drive a British-made Multisharp drill bit sharpener. Cost about 5 Euro, but I had a case, etc.


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## Biagio (Mar 2, 2013)

Actually, your best bet would be a 4000 W kit - handles 25 amps at max, about 20 Euro.
These kits are probably cheaper in the UK.


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## sunnybob (Apr 3, 2015)

Thank you all, I have finally had everything explained to me by a UK expert.

The controller issue that was concerning me was the apparent mis match between the watts stated on the controller, and the watts stated on the makita.
I seem to have gotten completely misled by doing calculations with online services that could not tell the difference between voltage and cycles.

At 230 volts and 50 cycles, my makita only needs 1400 watts, NOT 1800. so I can now buy the controller with confidence.
Thanks again.


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## Cherryville Chuck (Sep 28, 2010)

I had a feeling that was why you were only able to find 8 amp controllers in 230 volt. This question comes up occasionally so it's good to know the definitive answer.


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## DesertRatTom (Jul 3, 2012)

@Cherryville Chuck I'm trying to work out in my mind why the 50 cycle renders more powr output. Is that because the current is flowing for slightly longer each cycle? The difference in frequency would yield 16% increase in current flow, plus the higher voltage. I'm curious in part because I'm thoroughly familiar with 115 volt, 60 cycle electrical practices and theory, but completely ignorant about 220-230, 50 cycles.


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## Cherryville Chuck (Sep 28, 2010)

Tom I was only aware of it affecting rpm. A standard 110 volt 60 cycle motor of the most common rpm should turn 1800 rpm. Most are rated at 1725 or occasionally maybe 1750 and that's because the armature slips a few times a minute in the rotating magnetic field. Notice that 1800 is a perfect multiple of 60. I think the same motor on 50 cycle should turn 1500 rpm (with zero slippage).


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## Biagio (Mar 2, 2013)

@cherryvileChuck,
Take this from where it comes - I am a psychiatrist, not an engineer. I would much appreciate being corrected where misguided, by someone more knowledgeable.

My understanding is that in an induction motor, speed is directly proportional to frequency, and inversely proportional to the number of poles.
Routers have universal motors - they could run on DC, in fact better than AC, i.e. not frequency dependent. As far as I know, there is no theoretical limit to the speed of a universal motor, the limits are set by electrical losses (commutator), bearings and other friction.
Regarding power, the drawn amperage depends on the winding design and the load. At no load, there is very little amperage, as load is applied (voltage being held constant), more current is drawn through the windings, and could exceed the design maximum (burnt coil) under some circumstances. 
The speed of the motor is proportional to the voltage. One way of controlling speed (DC or AC) is with a rheostat - would also limit the current draw under load. The other, with a triac, introduces “frequency” again, in that the two halves of the sine-wave AC cycle are “chopped”, i.e. the pulses from the positive and negative cycles occur at different trigger points on the cycles. The maximum speed is at full sine-wave. The triac allows almost full current draw - the manufacturers phrase it as “full power under load - the speed control supplies more power when needed”. Actually, all it does is not inhibit the current that is normally drawn through the coils under load.
In summary, my understanding is that the power (volts X amps) is a function of the universal motor’s design ( e.g. coil wire gauge), and not related to the AC frequency.
Please “rectify” my misunderstandings.


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## Stick486 (Jan 4, 2013)

@Biagio...

will any of this help???

.


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## radios (Sep 30, 2009)

sunnybob said:


> Thank you all, I have finally had everything explained to me by a UK expert.
> 
> The controller issue that was concerning me was the apparent mis match between the watts stated on the controller, and the watts stated on the makita.
> I seem to have gotten completely misled by doing calculations with online services that could not tell the difference between voltage and cycles.
> ...


that's not how it works. 230 Volts at 8 Amps is actually 1840 Watts regardless of the frequency. P=E x I which is the power in Watts is equal to the Voltage times the Amperage.. routers use brushed motors.. btw, an induction motor designed for 60 Hz will get too hot at 50 Hz because it don't have enough inductance, which is why a motor for 50 Hz. is larger, more iron.. a motor designed to draw 1800 Watts at 230 Volts at 50 Hz. WILL draw 1800 Watts. btw, that's peak wattage, not average!.. from an MSEE..:wink:


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## radios (Sep 30, 2009)

DesertRatTom said:


> @Cherryville Chuck I'm trying to work out in my mind why the 50 cycle renders more powr output. Is that because the current is flowing for slightly longer each cycle? The difference in frequency would yield 16% increase in current flow, plus the higher voltage. I'm curious in part because I'm thoroughly familiar with 115 volt, 60 cycle electrical practices and theory, but completely ignorant about 220-230, 50 cycles.


 yes!. except that 60 Hz is 20% higher than 50 Hz...


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## Cherryville Chuck (Sep 28, 2010)

That's my understanding too Biagio that hertz and the number of poles in the motor is what determines the rpm. At no load the motor draws almost no power. It is running almost entirely on voltage. As you put drag on the armature it slows down and the magnetic fields of the armature begin running out of phase with the magnetic fields of the field coils (slippage). When this happens current draw increases to get the armature to catch back up again. The more slippage the higher the current draw.

That's about as much as I learned about motor theory. I had to learn it to get my power engineering ticket and it wasn't part of the physics I studied at university and the PE curriculum only had a couple of chapters out it. It sounds like Martin is far more capable of answering the questions than I am.

I'm not sure how much rheostats are still in use. They altered the resistance in a circuit and I remember the really old ones got pretty hot at times since they were essentially a heating coil. They may still be common in low voltage gauges. The fuel gauge on my fishing boat went and I took it apart to see if I could repair it and that's all it was.


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## Nickp (Dec 4, 2012)

radios said:


> that's not how it works. 230 Volts at 8 Amps is actually 1840 Watts regardless of the frequency. P=E x I which is the power in Watts is equal to the Voltage times the Amperage.. routers use brushed motors.. btw, an induction motor designed for 60 Hz will get too hot at 50 Hz because it don't have enough inductance, which is why a motor for 50 Hz. is larger, more iron.. a motor designed to draw 1800 Watts at 230 Volts at 50 Hz. WILL draw 1800 Watts. btw, that's peak wattage, not average!.. from an MSEE..:wink:



I seem to remember (and probably not that well) that frequency does affect power. Isn't there a frequency component in determining impedance in an AC circuit...? Impedance = 2 pi f L...? Frequency goes up, Impedance goes up, Current goes up, Power goes up...?


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## radios (Sep 30, 2009)

Nickp said:


> I seem to remember (and probably not that well) that frequency does affect power. Isn't there a frequency component in determining impedance in an AC circuit...? Impedance = 2 pi f L...? Frequency goes up, Impedance goes up, Current goes up, Power goes up...?


(current goes down, power goes down). that depends on what frequency the motor is designed for. a motor designed for 50 hz will draw more power, because of core losses, and deliver less horsepower at 60 hz, but will get very warm doing that, most likely way too hot. because you need to increase the voltage to get the same power. a motor designed for it's proper operating frequency will work at it's nameplate rating without drawing too much power and overheating. impedance works this way, increase the impedance on an AC circuit, and that decreases the current, so in in an AC induction motor, increasing the frequency requires a higher voltage to get the same power, because the inductance acts like a resistor at AC.. let's not get too involved in AC motor design, as not all the requirements are taught, but are developed by experimentation by motor designers, and kept as secret..


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## Nickp (Dec 4, 2012)

radios said:


> (current goes down, power goes down). that depends on what frequency the motor is designed for. a motor designed for 50 hz will draw more power, because of core losses, and deliver less horsepower at 60 hz, but will get very warm doing that, most likely way too hot. because you need to increase the voltage to get the same power. a motor designed for it's proper operating frequency will work at it's nameplate rating without drawing too much power and overheating. impedance works this way, increase the impedance on an AC circuit, and that decreases the current, so in in an AC induction motor, increasing the frequency requires a higher voltage to get the same power, because the inductance acts like a resistor at AC.. let's not get too involved in AC motor design, as not all the requirements are taught, but are developed by experimentation by motor designers, and kept as secret..



Thanks...ya gotta love secrets...


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## radios (Sep 30, 2009)

Nickp said:


> Thanks...ya gotta love secrets...


 you have to consider the time and effort that goes into motor design, including the salaries of Electrical Engineers, Mechanical Engineers, and Physicists, who have to work together.. an AC motor is not just a big pile of iron, the type of steel, the dimensions of the plates to reduce eddy currents, and maintain the needed inductance all matter, and the motor has to be able to withstand the heat, and desired mechanical forces desired.. all the while not making it too expensive.. it's a big expence, and if someone can make a copy easily, and sell it cheaper, it's all lost!..


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## radios (Sep 30, 2009)

btw, I doubt the OP has a 4.6 HP router.. 230V at 15 amps/740 watts.. that would have to be a huge and heavy router for that HP. the 15 amp rating is what would be used on 115 volts nominal.. at 230 volts, you only need half that amperage for the same power!.. 2.33 HP!..


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## mkoukkgou333 (Feb 21, 2020)

if it isn't a soft start put an external speed controller on it...


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