Collet Diameter vs tool

So I have been having issues where the tool pulls out of the collet during a job.

I have measured a few tools and all the collets, here is the problem.

Collet that came with the router - 6.32mm ID
2 Precision collets purchased from C3D - 6.38mm & 6.4mm ID

Collet 3.11 & 3.14mm ID

My tools from C3D measure.
6.3, 6.28, 6.28, 6.26mm

So the collets are large and tools run small.

The collet that came with the router gives me a tight fit when the tool is inserted, all the others the tool falls out.

Not sure what to make of this other than the “precision” isn’t very precise.

Anyone else measure collets and have the same slippage problem?

I had same issue
The collet that came with router was not an issue
I got the precision ones and had issues with the tools coming lose, especially when using a down cut
I got over it by not pushing the tool too far into the collet seems like the collet squeezes better onto the tool

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I also had problems, made several changes and something in this mix worked for me.

  1. Whenever I change bits, I take the old one out then use my dust collection hose to suck out/clean the collect (while it is still in the router). I started doing this when I noticed the quantity of dust that builds up within and on top of the collect. Enough dust that it was possible I was not getting the clamping force I needed because of the dust filled into the gaps.

  2. I retired a 1/8th collet after I mistakenly used it to clamp a metric bit. I blamed myself for over squeezed it, and decided it was better to punish my credit card rather than risk future bit slipping.

  3. I switched to Elair Collects but I don’t really think they are better… just took the mindset that these wear out just like bits do.

  4. @WillAdams once used the phase “monkey tight, not gorilla tight” when describing clamping bits within collets and that just kind-of stuck in my head.


when I change bits of any length, when inserting into the collet I hold the bit about .75, or a little less for .125 bits from the end, and allow my fingers be the stopping point.

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