# Router bit snapping



## Saw Dusty (Aug 12, 2011)

Help!!!!
I have gone through two 1/4" dia straight 1/2" shank bits trying to rout grooves for drawer bottoms, both bits snapped. I am doing this on a router table. The first attempt was going the full 1/4" depth the second was done at 1/8" deep and bang another snapped bit. Can someone point out what may be causing the failures of both bits. (two different brands of bits). I am now going to set up the table saw to complete my project (11 drawers)
Thanks


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## Phil P (Jul 25, 2010)

Hi Lou

By any chance did the cutters snap at the very top of the carbide flutes, where the shoulder increases in diameter to the 1/2in shank? And how powerful is your router?

I'm asking because I've had more breakages over the years trying to use small diameter cutters on large diameter shanks (mainly low-cost 1/4in and 3/8in straight cutters on 1/2in shanks) than on anything else. My "cure" was to go-over to using 1/4in (or 8mm) collets for tools of 3/8in (10mm) or under. Since changing my approach I've had no issues

Regards

Phil


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## IC31 (Nov 16, 2012)

Probably the only router bits (2) I've had break are those that I 'sank' too deeply into the collet and down to the radius which of course, knew better. I suspect that the 1/2" shank with a smaller diameter cutter would be even more susceptible to breakage at that cut back weak spot


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## Phil P (Jul 25, 2010)

IC31 said:


> I suspect that the 1/2" shank with a smaller diameter cutter would be even more susceptible to breakage at that cut back weak spot


Hi Gave

Yep, that's where they seemed to break for me, too.

Regards

Phil


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## Mike (Nov 22, 2004)

Plain and simple Lou you are putting too much pressure on the bit. You have to allow it time to make the cut and remove the debris. My guess is if you slow down on the speed you are feeding the wood over the small bit your problems will end. It takes about 3 times as long to travel the same cutting distance with a 1/4" bit that it does with a 1/2" bit.


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## jw2170 (Jan 24, 2008)

Phil P said:


> Hi Gave
> 
> Yep, that's where they seemed to break for me, too.
> 
> ...



Me three. The only bit I had break was a cheap 1/4" cutter on a 1/2" shank.


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## bobj3 (Jan 17, 2006)

I will 2nd Mike's post, A user error thing..over working the bit.

==




Mike said:


> Plain and simple Lou you are putting too much pressure on the bit. You have to allow it time to make the cut and remove the debris. My guess is if you slow down on the speed you are feeding the wood over the small bit your problems will end. It takes about 3 times as long to travel the same cutting distance with a 1/4" bit that it does with a 1/2" bit.


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## OPG3 (Jan 9, 2011)

The very few times bits have broken on my projects, it has been operator error. It's kinda like driving a car in bad weather conditions - one needs to have a feel for strain, control and over-exertion. In some cases, it can be as simple as hard spots in workpieces, dull cutters, dirty cutters, motor RPM and feed speed. This is one of the reasons my guys and I always use one router model, which in my case is the PC690. 3- copies of the same router makes expectations very predictable and means I am always up and running, same accessories are easily interchangeable, etc. 
*Note*: this does not mean that one person cannot use tons of different router models, it just means each one may have slight variations that may mess with one's learning curve.
Good luck, Otis Guillebeau from Auburn, Georgia


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## Saw Dusty (Aug 12, 2011)

That is where they snapped.
Thanks for the reply


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## Saw Dusty (Aug 12, 2011)

I would like to thank all who replied. The info and advise is really appreciated. I don't often use this forum but when I do I know everybody has a lot to offer. Thanks again.


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## damnitboy (Mar 3, 2012)

If you can check the material it should be 12L14 a leaded steel. it has flex in it which gives you a little forgiveness if you are feeding to fast. If you are feeding to fast you should get chatter or the cut leaning to one side. Also check your RPM'S you should have around 7200 surface feet, i.e. take your tool circumference multiply it times your RPM'S and divide by 12., that will tell you optimal spindle speed. Adjust to get the 7200 SFM Good Luck.
-Eloy


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## Everend (Mar 15, 2013)

Keep in mind that a 1/4" bit on a 1/2" shank is turning ~2x faster than a 1/4" bit on a 1/4" shank. ... no that's not right... I seem to remember something from high school physics about smaller diameter turning faster. Like a figure skater spinning. What am I thinking of?


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## Mike (Nov 22, 2004)

The larger the diameter of the bit the faster the cutting edge is moving.


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## Saw Dusty (Aug 12, 2011)

Thanks, I went to the table saw and daddo set-up


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