# HELP! My router bits keep breaking...



## trinibiker (Nov 12, 2009)

Hello all! 
I purchased a Porter Cable Router about 4 months ago and have been doing lots of dovetails with many domestic woods.
I have broken 5 router bits – ¼ inch shank 14 degree ½ inch
They are breaking at the shaft just above the bit itself – everybody I have talked to so far is stumped...

I am not forcing the cut
I make sure that the bit is not bottomed out
I am using a Rockler Dovetail Guide
I have used Rockler Bit s and Freud Bits
Any suggestions?
Thank you in advance for your time and input!


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## Marv (Nov 30, 2008)

Excessive runout in the router or a defective/worn collet can cause bits to break so you may want to check those.


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## sweensdv (Mar 3, 2008)

Maybe try a ½" shank bit.


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## Brian_Hinther (Sep 13, 2009)

+1 on ½-inch shanks. They're something like 4 times (or more) less likely to break than ¼-inch.


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## Leo G (Oct 16, 2006)

I had the same problem when cutting 9 ply plywood. Lots of glue. What happens is the bit is getting hot enough to remove the temper and then the bit shears at the weakest point. Look at the break. Is it crystaline looking?

WHat I did to solve the problem is to cool down the bit after every full pass of the drawer. It became habit. You do the pass, cutting the full edge, put the router down (turned off) and blow out the chips on the drawer. Then take the air and blow on the bit (close, almost touching) for 10-15 second. 

After I started doing that I got so many more drawers per bit. At one time I was getting about 6 drawers per bit using quality bits (whiteside, CMT, PC) After I started cooling the bit down I was about to get mor than 30 drawers per bit before breakage. Average was probably about a 5 1/4" drawer.


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## Jacktoo (Oct 8, 2009)

I've used the same bits you are and have never broken any, I agree with the 1/2" shank, other wise my advice is to contact John at wooddjam.com and ask him. He will find the answer.


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## Marv (Nov 30, 2008)

A 1/2" diameter 14 degree dovetail bit with a 1/2" shank has about the same diameter "weak point" as a 1/2" diameter 14 degree dovetail bit with a 1/4" shank (the area where the flute meets the shank) so I don't think that will solve the problem. If the router and collet are OK I'd have to agree with Leo that excessive heat is the issue.


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## GeorgeC (Jul 30, 2008)

trini, do you do any other routing besides using the dovetail bit. If so how do the other bits perform? Do you use any of the others as much as you do the dovetail?

Getting a new router may be nice but it is also costly. Hopefully you can find a root cause of this problem.

George


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## Leo G (Oct 16, 2006)

Marv said:


> A 1/2" diameter 14 degree dovetail bit with a 1/2" shank has about the same diameter "weak point" as a 1/2" diameter 14 degree dovetail bit with a 1/4" shank (the area where the flute meets the shank) so I don't think that will solve the problem. If the router and collet are OK I'd have to agree with Leo that excessive heat is the issue.


The larger mass of the bit will slow the heating down and provide more area for head dissipation.


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## trinibiker (Nov 12, 2009)

*Thanks for the suggestions...*

Thanks for all of your input. 

The collet is good - I had the whole router replaced by the manufacturer just incase of defect a couple months ago, but that didn't change anything.

Heat - I only do 4 cuts (and they are small boxes - so that is not very much) and then the router has a long break in between uses - it will be a bummer if that is the problem as it will really slow up my production

I am going to try just a straight bit on just some scrap and see what happens - I will let you know the results


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## Charles M (Dec 10, 2007)

It is often advisable to use an appropriately sized straight bit to plow the slot before using the dovetail bit. If you hear the bit "scream" in the cut it is likely overworked and a stress fracture can occur. By removing some of the material with a straight bit you reduce the stress and provide a better path for the chips.


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## Leo G (Oct 16, 2006)

What happens if you heat the bit up and let it cool slowly is the metal will lose its temper and it will break easier. If you cool it quickly it will remain hard.

Make you cuts, let the bit spin down to a stop and then use compressed air and cool the bit down for 10-15 seconds, every time. Solved my problem


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## skymaster (Oct 30, 2006)

Sir Charles, you hath stolen my comment ROFLOL.
Oh by the way Congrats to all the folks at Freud I do really like your products.


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## nicewood (Sep 15, 2009)

Don`t allow the bits to get blunt this puts pressure on them


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## Marv (Nov 30, 2008)

Leo G said:


> The larger mass of the bit will slow the heating down and provide more area for head dissipation.


My comment was directed towards the possibility that deflection was the issue due to a faulty router or collet. :smile:


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## Jacktoo (Oct 8, 2009)

You may want to try what porter cable recommended years ago with their omnijig. Make a skim cut from right to left and then move the router left to right around the template guide. Move the router slow and easy and let it do the work. I agree with the straight bit only if you have two routers otherwise you may have a continuous set up issue.


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