Thread: Collet not holding bit properly?

Gday Richard, only thing springing to mind is that the bit shafts should match the collet in your router, ie. 1/4" bits in a 1/4" collet, and 6mm bits in a 6mm collet, but not 6mm bits in a 1/4" collet - the fit would be way too sloppy and the collet would have to be tightened up way too much IMO to be satsfactory or safe.

Pull the collet out of the router, give it a good cleanup, roll up a bit of fine wet & dry sandpaer & spin it in the collet to clean up the inside surfaces, & make sure there is nothng preventing the collet closing up properly, and then just use the correct sized bits. Ensure the bit shafts are free of crud & rust, too, fine w&d is good for this also.


Cheers......................Sean

G'day Richard,
What Sean said is the dead set truth!!
The only additional info I can give after you've done what Sean recommended, is to make sure that the bit is not bottomed out in the collet space.
That is, push the bit in until it can go no further, and then pull it out a bit as you tighten the collet.
For some reason router bite come out of the collet during use if they are "bottomed out"
My two cents worth.

Yeah, good point Noel

Thanks for the advice folks. I re-checked the Dimar bit I mentioned - it is 6 mm cutter dia, not shank, that is 1/4 inch (within 5 tho) so it should be OK. It is actually quite new...still has the name etched on the shank.

Don't think it is bottomed out, but I'll check that too.

I'll clean it all out and try a bit of wet and dry on the collet and make sure everything is seating OK. If it slips again I'll take it to a powertool shop and get them to look at it.

I can do without bits coming loose!!

Following up - I cleaned the collet and more particularly the nut holding the collet down - the thread was full of dust so may have been preventing it tightening down properly. I tried it out with a deep cut and the bit didn't move, so I hope that has fixed the problem.

I usually kep the bits clean with CRC, so perhaps oil on the collet is also a bad idea so I'll clean the shanks with turps before inserting into the collet as well.

New policy - clean and inspect the collet and nut each time I change the bit in future!!

Thanks for your help.

I've had this problem a few times too: very scary. Only solution was to do up the collet REALLY tightly.

Read this earlier and just realized its what happened when making my stone boxes.
scary stuff glad I had a block over the top as I was doing it in the router table and to a depth that left only 3 mm it tore it badly.

I sort of laughed at the fellow a Bunnies when he said buy a few extra collets they do ware.

I am now wondering if the champer on the nuts and collets are allowing them to come loose. If you over tighten this could force the collet to bucke leaving just the tip holding the shaft not the whole grippy part of the collet.

I bought a new collet when it happened to me a while ago, however, the problem I had the other day was with the new collet, hence this thread. I think in my case the original collet was probably OK and I'm just not keeping it clean enough, well, that what I hope. Time will tell.

Not sure about overtightening causing a problem. The new collet I got for my Makita only had a single slit and was very hard to do up (new design) so I had to tighten it with a fair bit of force. The original is much nicer and tightens much more easily.

Hi All,

In my experience, if you're tightening anything with force there is something wrong. I have a lot of routers and a lot of different collets types. Giving them a quick blow out with the air compressor every so often is all the maintenance they require.

Problems with over tightening include the following:

• Bit shaft burring
• Over stressing over spindle lock mechanisms (if present)
• Stress on table mounts (machines with spindle locks)
• Problems when loosening again
• Collet damage

The tip that bits should not be insterted till the end is spot on. The micro vibrations caused by metal on metal work against the clamping force. The same is true of hammer drills (cam plates - not pneumatic). A small spring inserted into the bottom of the collet recess on table mounted machines takes care of this.

I bit of common sense and a good feel for pressure feedback is all that's necessary to prolong the life of any tool.

Damien

Here are the collets. The original has 4 slots. It is easy to do up. The newer version has a single slot all the way through and 2 rebates. It is a devil to do up and doesn't release the bits easily. That is the one that slipped recently, but probably because it wasn't clean.

So, Damien, I suppose , the ''something wrong'' is what I'm trying to get to the bottom of (why is this hard to do up and why wont it release). Any suggestions?

BTW, I like the spring idea.

Hi Richard,

I would be interested in seeing these collets from the side - the reason being the outside diameter of the tops and the angle/length of the taper.

There are two main types of collet. (not counting the full-grip and half-grip slit variations)

Type 1: The entire outside edge (from bottom to nut lip) is tapered

Type 2: Only the top section is tapered.

The clamping force of the type you have (type 2) is wholly dependent on the effectivity of the comparatively small taper length... If you see that there is a difference, you will be able to see why one is clamping better than the other. I very much doubt it has anything to do with the inside tollerances because these parts are precision ground.

Damien
PS. The old Makitas I have work by screwing the tapered collet into the nut and while you need two spanners, the suckers hold on like there's no tomorrow...

Hi Damien

yes my Makita requires the 2 spanner approach.

Here are the side views. Slight depth of field problem! The newer one on the left shows a bit of wear on the side, that was me today removing a slight burr where the collet has been cut with wet and dry. Otherwise, both seem to me to be in reasonable nick. The inside bore isn't heavily scratched on either. The only obvious wear is on top where the nut screws down on the collet. As mentioned the newer one seems to jam in to the router and I have to tap the bit with a piece of wood to release it usually.