Broken router bit Q

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Forum topic by unclearthur posted 04-29-2016 04:49 AM 501 views 0 times favorited 6 replies Add to Favorites Watch
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5 posts in 1208 days

04-29-2016 04:49 AM

I purchased some inexpensive non-brand name “plywood” router bits and was using the 15/64 bit to cut a 1/4” deep dado in some drawer sides (which would be fitting a 1/4” plywood drawer bottom). Was doing the dado in 2 passes on a router table, so each pass was around 1/8” only.

Did a couple cuts through some maple pieces OK then part way through a Cherry piece, the bit broke in half.

Is this common? Bad bit? Or was I doing something dumb?

Seems a bit dangerous.

Thanks for any replies.

6 replies so far

View jerryminer's profile


497 posts in 861 days

#1 posted 04-29-2016 05:52 AM

Yeah. I’ve had that happen and had the carbide fly off of a cheap bit before, too.

I don’t buy “bargain” bits any more.

I use Whiteside, Amana, Infinity, CMT

View joey502's profile


482 posts in 938 days

#2 posted 04-29-2016 08:54 AM

All bits that small can be broken but the cheap ones seem more likely to fail. The cut does not seem excessive. Were you possibly feeding the board too fast? By that did it seem to cut the wood easily at the rate you were pushing it?

I also like the Whiteside bits and Freud. They both provide good quality without breaking the bank.

Do you have a table saw? I cut dados for drawer bottoms at the TS. You can get a very nice fit by creeping up on the width.

View unclearthur's profile


5 posts in 1208 days

#3 posted 04-29-2016 10:23 PM

Yeah, I finished the dados with a table saw which is fine, but I just never broke a router bit like that before and was a bit surprised. If it was a different type of cut it could have been quite dangerous. Don’t think I was going very fast …... anyways, no more discount router bits for me.

View johnstoneb's profile


2104 posts in 1593 days

#4 posted 04-30-2016 12:25 AM

I’ve had several 1/4” bits fail like that one, cheap and expensive. You are probably feeding too fast for the amount of the cut.
That was my problem made 3 passes instead of 2 and cured the problem until the next time.

-- Bruce, Boise, ID

View splintergroup's profile


724 posts in 642 days

#5 posted 04-30-2016 02:37 PM

Had the same thing happen as well, good bits too! (Whiteside).

First problem is the diameter. 1/4” can’t take much of a side load. Even if the bit is only bending slightly, the metal fatigue will accumulate.

Aside from the usual tips about cut depth and feed rate, solutions are to either use 1/2” shaft bits, or use a bit that is much shorter to reduce the leverage.

After my grief with breakage, I started using “stubby” 1/4” end mill bits. 100% satisfaction!

Enco always has free shipping offers and/or 25% off deals (if you are on their mailing list), but there are plenty of other sources. Shorter bits are also much cheaper.

View Ripthorn's profile


1402 posts in 2405 days

#6 posted 04-30-2016 03:01 PM

This is a problem common not just to router bits. What happens is that if it is a carbide tipped bit, the body is hardened steel and the carbide is brazed on to it. Really cheap imports tend to have steel that is overhardened (not properly tempered). This results in the hardened steel being very hard, but also very brittle. That means it can’t take very much lateral deflection before breaking. Same is common in end mills.

-- Brian T. - Exact science is not an exact science

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