Bits coming loose?

I have a Shapeoko XXL and I’m loving it. I use the carbide router. I’ve done about 20 projects with no issues, until now.

Mid-project, I heard a noise change to I hit pause and somehow the 1/4" spiral downcut bit had somehow pulled out a little and my Z was all messed up. So I restarted, and sure enough about 30 seconds in, the bit pulled out again.

The bit looks fine, the collet looks fine to the eye.

Is it possible I’m tightening TOO much? I put the wrenches on and give it a good snug tightening. I could go harder if I wanted to break the little wrenches they ship with the machine, but is it possible that if you tighten TOO much, it can let go? I’m trying to figure out if I’ve been tightening right. The fact I hadnt run into issues til now made me think it was tight enough. But if I had to say, I’d say I tightened it a bit extra these 2 times.

I’m 99% sure I backed the bit out 1/8 to 1/4" out before tightening, but honestly who knows.

The bit gradually pulled out both times. I can feel what was supposed to be a straight flat cut and it drops very smoothly. I’m cutting MDF so the bits shouldn’t have any issue.

Just wondering if there’s some troubleshooting I can do before I replace the router part.

I have an extra collet I can try. (the one Ive been using has 4 ‘grabbies,’ my spare only has 3, although I can’t see that being an issue. Any other ideas? Tightening tips? Things to check/clean?

Are you positive you have a 1/4" bit? I have a few 6mm bits that the collet can grab onto but not tight enough. Had to go out and get a 6mm collet for them to work properly. Ran into this buying bits off ebay.

Also make sure that the collet, collet nut, and the collet holder are completely clean. Saw dust build up could cause it to not fully seat into the collet holder and not make a good grip even if you snug it down.


Yeah, it’s been the same bits I use on all my projects. It fits so perfectly into the collet that it almost makes a suction, haha. I will check out to make sure it’s fully clean in there. Honestly I don’t check that often. I assume a can of air shot up into the holder would probably do

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I would take it off the machine so you can look down in there, but yeah canned air should get it out if it is dust build up.

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A collet should be clean with no lubricant at all. If you have some brake cleaner you can spray the collet out with that. The brake cleaner will de-grease the collet and the nut and you can puddle the brake cleaner and dab a qtip in and clean your router shaft inside. My understanding of the Makita and C3D router is the collet is not captured by the nut. So when you put the collet and nut in the router you put your bit in and tighten by hand until our bit will stay in and then use your wrenches to tighten. So when you loosen the nut the collet will try to spring out and will slip down and the bit will come loose. The inside of the router shaft is an inclined plane, larger at the bottom getting slightly smaller towards the top.

Measure your overall collet length and make a mark on your bits with a black marker. Your bit should be seated up to the black mark for best grip of the bit. If you do not have the bit seated enough it can come loose and if you have it seated too far up inside that can cause the bit to run out of round and rough causing it to come loose. So lets say the collet is one inch long. Your bit should be inserted at least one inch into the collet but not much more. You never want a bit to bottom out. The collet when tightened pushes the collet slightly up inside the router shaft and if the bit was already bottomed out there would be nowhere for the bit to go.

Collets do go bad and may need to be replaced occasionally . I like the collets from Make sure you find your model router as they have a lot of models to choose from.


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