# new member - question on avoiding this problem in the future



## hobbywwer (Jun 30, 2012)

Hello everyone,

I'm new here and I have a question. I was routing 1/4" dados across the grain on a set of 5" wide boards for drawer joints, when the 1/4" in bit broke and went into the router, destroying the fan and armature and tripping the breaker. Needless to say the router is ruined (and I just had the bearings replaced). I've broken off bits before but they've never gone inside the router causing all this damage.

I'm scared to use another 1/4" straight bit, so how can I prevent this in the future? I suspect that 1/4" depth was too much for the bit so it overheated and snapped off, perhaps going in 1/16"s or even 1/8"s depth would help?

I had the router mounted on a table where I've had trouble free use for years.

Off to buy a new router now... looking forward to your replies.


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## DaninVan (Jan 1, 2012)

On the bright side, n/a, nobody got hurt, eh? Better a shopping trip for a new router (1/2" collet this time?) than a trip to the ER!
On a much happier note, Welcome!
Cheers,
-Dan


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## MAFoElffen (Jun 8, 2012)

Usual rule of thumb is 1/4 inch a pass on soft wood with a sharp bit. I usually adjust the less for some harder hardwoods.

More important than the rule of thumb for tellling me- is what I feel, what I hear, what I see and what I smell. 

If the feed rate feels like it is dragging.... If I hear it dragging... If I see smoke other than from moisture... If I smell other than the smell of cut wood, such as burning... 

On large diameter bits, I test to see how much I can take off at a time. On knots and burls, I take off less at a time and crawl.

Even after all that, for some reason, after routing often for so long, it still might happen. About 4 times in 20 plus years, routing almost every day. I'll never get used to that sound. I think over half of them was my fault, thinking I could go a few more time with a dull bit, going too deep with too fast a feed rate. 

Next, I use a bit insert ring somewhat close to the size of the bit. The main reason for that is to keep excess sawdust off... Secondary, (has happened with me, so) is far safety. If the bit breaks it'll slow down the pieces as it rips apart the insert ring. 

I can't say that any of my router's exhaust ports have an opening large enough for a 1/4 bit to enter, like your's did.


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## hobbywwer (Jun 30, 2012)

Thanks all. I ended up buying another Porter Cable 690 for $184 + tax. I was using a 1/2" shank, 1/4 straight bit. IMO they make those things too long. If the bit was 1/2" tall only there would be less torque on the metal.


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## Mike (Nov 22, 2004)

N/a, my guess would be the bit may of been dropped creating a hidden defect? Other possibilities are you were trying to feed the bit too fast, hit a knot or started the router in contact with the material? Any of these could cause the bit to break, it sometimes happens.


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## Phil P (Jul 25, 2010)

Hi N/a......

The "square" rule stated above is correct, but there are several other facrors to note: you can generally feed slightly quicker with dust extraction than without (and the bit stays cooler), single flute cutters clear waste better than 2-flute cutters - which is why they were used for production pin routing from the 30s to the 80s (albeit the quality of the cut is not as good as two flutes) and spiral upcut bits clear waste better and can be fed much faster than other designs. Spirals are the one cutter design which may allow you to exceed the "square" rule (i.e. depth per pass must NOT exceed diameter of cutter), but not by much

Regards

Phil


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## jw2170 (Jan 24, 2008)

G’day

Welcome to the router forum.

Thank you for joining us.

That also happened to me, once. I am still not sure why. I was using a 1/4" cutter with 1/2" shank and only taking a 1/4" bite in soft wood.

Mine was an older cutter from a cheap set.

How was your feed rate? Sometime, if we have a few to do, we tend to push through a bit quicker.


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## hobbywwer (Jun 30, 2012)

I started feeding it at a normal pace, but I fed it a bit faster near the end. The wood was hard maple too, something I've never routed before, so you could say these two factors caused it. The bit and router were hot to the touch when the breaker tripped, unlike now that I reduced the depth to 1/8" and reduced my feed rate. That also helped with tearout on exit.

Its 12 drawers with lock joints so its 24 boards with 1/4 grooves for the front and backs.


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## AndyL (Jun 3, 2011)

jw2170 said:


> That also happened to me, once. I am still not sure why. I was using a 1/4" cutter with 1/2" shank and only taking a 1/4" bite in soft wood.
> 
> Mine was an older cutter from a cheap set.
> 
> How was your feed rate? Sometime, if we have a few to do, we tend to push through a bit quicker.


I've done exactly the same, though with a 1/4" shank bit. I suspect I was feeding too fast too, though it didn't feel like it was straining. I guess it doesn't take much excess force to break a cutter that small, so best to err on the side of caution with the feed rate.


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## mgmine (Jan 16, 2012)

I have found that the router takes too long for just the reasons mentioned. When I need a dado I reach for the dado blade and do the job in a fraction of the time on the table saw. I learned the hard way by burning out the speed control on my router.


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## Dmeadows (Jun 28, 2011)

I have to agree with Art. In most cases, I prefer to do dadoes on the table saw. Or sometimes the RAS if the boards are less than 16" wide.


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## DaninVan (Jan 1, 2012)

Art; heh...I was keeping my lip zipped, being how the topic was routers... 
...but yeh.


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## hobbywwer (Jun 30, 2012)

mgmine said:


> I have found that the router takes too long for just the reasons mentioned. When I need a dado I reach for the dado blade and do the job in a fraction of the time on the table saw. I learned the hard way by burning out the speed control on my router.


I had considered using the wobble dado blade to run the cuts, but a) im too lazy to change the blades on my TS and b) if I remember correctly this dado blade produces a lot of fuzz and tearout across the grain, not that the router was better at it. At least going in 1/8 increments with the router it reduced the tearout.


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## hobbywwer (Jun 30, 2012)

Here is the cabinet for the drawers I'm making...


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## DaninVan (Jan 1, 2012)

Phil; wobble dado blades leave a channel wider at the bottom than the surface. That can leave a loose joint when the mating piece is inserted. Also be really careful with it; a buddy's radial arm saw with a wobble dado nearly took my hand off...many stitches but thank G*d , no tendons or nerves were permanently damaged. Grabbed the piece I was working on and fired it clear across the basement, stopping only long enough to rip into my paw. Haven't used one since. (That's my worst accident work related. Tearing my Achilles tendon, moving boulders, was just my body telling me that I'm not 25 anymore...


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## hobbywwer (Jun 30, 2012)

DaninVan said:


> Phil; wobble dado blades leave a channel wider at the bottom than the surface. That can leave a loose joint when the mating piece is inserted. Also be really careful with it; a buddy's radial arm saw with a wobble dado nearly took my hand off...many stitches but thank G*d , no tendons or nerves were permanently damaged. Grabbed the piece I was working on and fired it clear across the basement, stopping only long enough to rip into my paw. Haven't used one since. (That's my worst accident work related. Tearing my Achilles tendon, moving boulders, was just my body telling me that I'm not 25 anymore...


One of the reasons I don't use my wobble dado is because it "feels" unsafe, so you got it right there.


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## AndyL (Jun 3, 2011)

hobbywwer said:


> Here is the cabinet for the drawers I'm making...


Looks like a really elegant cabinet Phil, I look forward to seeing the completed result.


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## tdacon (Jun 20, 2012)

*Stubby bit*



hobbywwer said:


> Thanks all. I ended up buying another Porter Cable 690 for $184 + tax. I was using a 1/2" shank, 1/4 straight bit. IMO they make those things too long. If the bit was 1/2" tall only there would be less torque on the metal.


LeeValley has a stubby straight bit that might be what you're looking for. It's cutting length is only 3/8". Unfortunately they only offer the bit with a 1/4" shank, but it might still be pretty good for what you're using it for.

I can't post URLs here yet but just search the Lee Valley site for "stubby straight bit".


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## TRBaker (Jul 5, 2012)

Back in 1979 I shredded a Crapsman router with a broken off 1/4" shank straight bit that broke. Since then, I use a regular dado blade for dados and if I have to cut anything with a straight cut bit, I use 1/2" shanks. I too was using a table mounted router and the bit dropped straight down when it broke. Sure made it exciting for a moment.

Troy


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## Jerry Bowen (Jun 25, 2011)

I have not experienced tha excitment you is being discussed on this subject and hope that I never do. The odds of my not having the experience of breaking a quarter inch straight bit have been greatly reduced due to reading about what has happend to you guys that replied to this thread. Thanks for the lesson. I am going to be much more careful with all of my routing and/or other work for that matter.

Jerry


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## hobbywwer (Jun 30, 2012)

AndyL said:


> Looks like a really elegant cabinet Phil, I look forward to seeing the completed result.


Here she is...


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## dustmagnet (Jul 24, 2012)

Very nice Phil,
Have you considered using a slot cutter, but you do have to remeber, in woodworking, patience, patience, patience, and then some more.


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## walowan (Jan 21, 2011)

The only router bit I have broken was a keyhole bit, since then I use a straight bit first, then the keyhole bit.
I always use a table saw for rabits and dadoes........


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## davcefai (Aug 3, 2009)

There was a time when I considered setting up a fund to buy 1/4" bits but instead I learned patience.

The "square" rule mentioned earlier seems to me to be optimistic when it comes to 1/4" or smaller bits. I personally limit my cut depths to 4mm in softwood and 2-3 mm in harder woods.

I do woodworking because I enjoy it so the longer it takes, the more fun I'm having. (one day I'll actually start to believe that!)

Incidentally dado blades are illegal in Europe* so we have to learn patience.

*No law saying this specifically but the tablesaw safety rules rule out their use.


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