Breaking bits over tightening?

I have broken a quite a few bits they always seem to break off 4mm at the tip (not the cutting end) I think it a result of over tightening the collet, because I really keep my travel speed to a minimum for this exact reason. I find it difficult to determine the amount of pressure applied to the collet, because I have also had issues with the bits coming loose. Does anyone have any suggestions? They are much needed, and much appreciated! Thank You

i don’t think you can over-tighten the collet tbh.

would be the first I hear of it anyways.

what are you cutting at what speeds? and which endmills?

Try changing out your Collet Adapter.

When I first started with my X-Carve I broke a lot of bits too. I changed my collet adapter. I bought one from for something like $8 and I have not broke a bit since. May be worth a try.

Try a search on the forum… There is one specific Collet that is highly recommended but I do not remember the name.

Please post a picture of some of your broken bits.

I am curious about how deeply you are setting the bit into the collet.
Typically the bit should be inserted “bottomed out” into the collet and then withdrawn by about 1/16 " before final tightening. the reason for this is, as the collet grips down on the bit, the action of the collet nut pushing the collet deeper into the router/spindle shaft tends to take the bit with it. If the bit is too deep, the collet wont tighten properly, too shallow and the possibility of broken bits rears it’s ugly head.
But the part about a consistent 4mm break point has me scratching my noggin…

If you’re using a collet adapter, stop and buy an Elaire collet or at least, as suggested by another, get a new adapter. Those collet adapters do make it easier to break bits. I’ve found that an actual collet is worth any additional cost.

As for the 4mm part, is that where the cutting edge stops and it goes to the shaft of the bit?


I am using a collet adapter, and I fact I have replaced it with a new one. I was unaware of any issues with these adapters, I will check out Rockler and the Elaire collet as Justin said. Thanks for the help everyone!

Make sure you’re pushing the bit all the way thrue adapter. It will be out of balance and break it half if bit half way in the adapter. Common problem.

Thanks everyone for all the help. I ordered a Elaire collet it is $13.00 more than the replacement adapter, to bad that Inventables didn’t include this with the Xcarve. I would have gladly paid an extra $13.00 at the time. To save all the broken bits and messed up projects.

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Brian can you post the elarie collet part number you ordered. I’m having the same issue