Router Collet Design Question

[wjt]

While keeping the brain cell engaged today I noticed different types of collet designs on routers.

The number of slots / kerfs vary from 1 to 8.

Some with multiple slots / kerfs have them only on one end of the collet. Others have half on each end offset by 90°

Some have the collet and nut as one assembly others the collet and nut are separate.

Is there a minimum distance that a bit should be inserted in a collet? My default approach has been to insert the bit as far as possible then retract it about 1/8" The reason for the question is a new tool in the shop (a CNC router) and some of the bits are short and would not leave much for cutting if I use my default method.

Just out of curiosity could someone explain these design differences and the minimum insertion depth question.

Thanks, Bill

[Turner52]

I have always been told to use your method. Insert fully and then retract 1/8". Have never had a problem. Have no experience with cnc . Hopefully someone that knows can give you thr correct info

[fixtureman]

On my CNC I insert short bits just o the shank is in far enough that the collet has full contact with the shank

[Stwood_]

I put o-rings down into the shaft on most of my routers several years ago. That takes the guess out of pulling the bit back up 1/8"

[Bob Barkto]

While keeping the brain cell engaged today I noticed different types of collet designs on routers.

The number of slots / kerfs vary from 1 to 8.

Some with multiple slots / kerfs have them only on one end of the collet. Others have half on each end offset by 90°

Some have the collet and nut as one assembly others the collet and nut are separate.

Is there a minimum distance that a bit should be inserted in a collet?  My default approach has been to insert the bit as far as possible then retract it about 1/8" The reason for the question is a new tool in the shop (a CNC router) and some of the bits are short and would not leave much for cutting if I use my default method.

Just out of curiosity could someone explain these design differences and the minimum insertion depth question.

Thanks, Bill

You want the shank to fully engage the collet. The closer the cutter head to the collet the better. Never let the cutter shank bottom in the tool shaft.
The number of fingers is not really much of a concern. The more fingers on the collet the better the grip in theory with shanks that are not perfect. But multi-fingered collets are more fragile.
If your cutter is too short, get a longer cutter. No sarcasm intended, just mechanics. Keep in mind, the longer the cutter in relation to the collet length the more chatter you can get.
The collets that seem to be attached to the nut are usually removable, held in with a snap ring. They do this because the multi-finger collets are a bit fragile and it makes damage less likely to keep a nut with the collet on multi sized setups. Also quicker to change sizes.. They can be removed from the nut for cleaning/replacement.

[rahulnaik]

i usualyy put my o ring into my shaft then I would pull it back 1/8th inch