This is beyond frustrating. I tighten the heck out of my router bit in the colette and it slides mid cut. How do I prevent this?

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Also, how come they don't make routers with the SDS+ system of locking bits in the chuck/colette so there is no way for them to slide? Like hammer drills.

  • 1
    What is the size of the collet and the advertised size of the bit shank?
    – Jason C
    Commented Dec 22, 2015 at 21:49
  • 1/2" both colette and bit
    – amphibient
    Commented Dec 22, 2015 at 21:56
  • 1
    Does this happen with multiple bits or have you only observed it with one?
    – Jason C
    Commented Dec 22, 2015 at 22:01
  • 1
    (BTW, minor nit picking: in hammer drill chucks SDS provides rotational locking but intentionally allows axial movement; although in rotary drill chucks it provides both. Source, SDS US Patent)
    – Jason C
    Commented Dec 22, 2015 at 22:03
  • 8
    Take the collet fully apart and clean out all sawdust and other debris. In past I have had this be the cause for exactly what you have happening here. Commented Dec 23, 2015 at 13:33

3 Answers 3


If your router bit slips, there are several possibilities:

  1. The bit is improperly installed. When installing the bit, let it drop in as far as it will go, then lift it about 1/8". On most bits, there is a small angled collar where the head meets the shank. If you tighten the collet around this, the collet will inevitably lose its hold and the bit will slip out during operation.
  2. The collet or bit is damaged and the collet cannot tighten properly around the bit. It's possible you've overtightened the collet in the past, but collets can also wear out with use over time.
  3. The collet and/or bit shank needs to be cleaned.
  4. You are taking too heavy a cut (this can be compounded by cutting too fast or using a dull bit). Remember to take small bites with a router.
  5. You are not tightening the collet as much as you think you are. (Though, as previously noted, it's also possible to overtighten the collet and damage the collet and/or the bit.)
  • The only time I had this happen to me was taking a full cut on a very hard wood. The cut is in cross grain oak, and an ogee sill profile, a lot of wood flying.... I see no evidence of multiple passes.
    – Jack
    Commented Dec 26, 2015 at 18:49
  • #1 is critically important and in my experience the major cause of slipping bits (well, given normal care and cleanliness to avoid #3 and spot #2 )
    – Ecnerwal
    Commented Mar 26, 2017 at 14:46
  • For point 3, see also Nick Engler's youtube.com/watch?v=GAuOV4IpHMk&t=2s
    – peter a g
    Commented Apr 17 at 1:16

If this is a new router, perhaps it is possible that you have a defective machine with a damaged collet, or a piece of debris is jammed in the collet. If you have only observed this on a single bit it's also possible that your bit has a defective shank or another quality issue.

Be sure to also obey the minimum insertion depth marking on your bit if it has one (or insert it all the way and then pull out maybe 1/8" tops if it doesn't).

Be sure you are using the correct size as well, e.g. don't use a 6mm bit in a 1/4" collet.

Your collet should be locking your bit in place, even without you having to crank as hard as you can when tightening it.

  • 2
    This is pretty much what I was going to say. That shouldn't happen and since it obviously does, either the parts don't match correctly, or there is a defect.
    – bowlturner
    Commented Dec 23, 2015 at 14:17

If the collet is worn, replace it. They can wear out through usage (although that is uncommon). They are often damaged by mishandling and accidents to the router. Check with the router manufacturer to get a replacement.

If the collet isn't worn, then you need to follow the manufacturer's instructions on tightening to properly hold the bit.

Lastly, if the bit isn't the correct size for the collet, you should switch to a bit that is the correct diameter. You could have significant safety issues by not doing so.

  • 1
    The router is pretty much brand new
    – amphibient
    Commented Dec 22, 2015 at 21:37

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