Collets? how and why?

[ZipSnipe]

Being the newbie that I am to milling. I had seen several mills that sport a drill chuck and I had at one time thought that I could convert a drill press to a milling machine(i,m kinda givin that idea up). And someone said that the chucks were not made for milling. So my question is these collets which I assume are the mill holders, I can,t tell how you tighten down the mill cutter. With a drill chuck it make sense but the collets, I can see that they clamp around the mill cutter but I can,t tell how they get clamped down. Any one care to educate me on this?

[WhiteTiger]

There's a threaded drawbar down the center of the spindle that screws into the back end of the collet and pulls it up into the spindle. The working end of the collet has a taper on the outside. When the drawbar pulls the taper on the collet into the taper seat in the spindle it forces it to clamp down on the cutter and the spindle, collet and cutter are all friction locked together like a workpiece clamped in a vice.


Tiger

[JRoque]

The drawbar is one method, as explained above. Another method, and the one on mine, uses a nut. Here's how that one works: the spindle has a taper carved on the bottom end (where the tool goes) with a thread on the outside. You insert a matching collet inside this taper and tighten up the nut. The nut pushes the collet up the taper which then squeezes the cutting tool. The more you tighten the nut, the stronger is the squeeze on the tool. I use an ER25 collet system. Collets, by the way, have cuts made along their bodies to allow them to squeeze and shrink their diameter.

A drillpress and chuck is not the best for milling - though I have milled on a drill press when my mill was down and I needed to make some rough cuts. The reasons are that the drillpress cannot generally take the side load needed to mill. Anything more than slight side pressure causes it to rattle and can break the bearings. Drill chucks are also not good at side loads because only 3 jaws hold the tool. There's also the runout which is usually rather large on a drillpress as compared to a mill.

JR

[Geof]

Have you ever used a compression fitting on copper tube? Collets work on the same idea.

The type that uses a drawbar (long bolt from the top of the spindle) to pull a tapered collet into a matching taper inside the spindle can only grip the tool size they are made for. The collet has splits so it can open slightly to allow the tool to be pushed in but because the splits are only at one end as the collet closes up in the taper the sides of the hole will not be parallel if the tool is smaller than the collet is designed for.

The other type that are pushed into a taper by a nut (very similar to a compression tube fitting) often have a taper inside the nut as well as the body of the collet and there are two sets of splits from each end of the collet. This means the sides of the collet gripping the tool are compressed in more or less parallel so these collets can have a range of grip that can be as much as .039".

[ZipSnipe]

Thank you gentlemen, I now stand educated... I could never tell from any pics that seen of them and I figured it might be like the compression fitting idea.
One more question what is an arbor?
Thanx again.

[phil burman]

Try pasting this phrase into Google and then click search:

arbor+definition

Google is a wonderful tool for improving anybody’s education.

Phil

Originally Posted by ZipSnipe Thank you gentlemen, I now stand educated... I could never tell from any pics that seen of them and I figured it might be like the compression fitting idea. One more question what is an arbor? Thanx again.

[ZipSnipe]

Thanx I found it

[ZipSnipe]

Ok just when I was starting to comprehend collets , I was looking thru Grizzly's Catalogue and saw end mill holders. Now can and end mill holder and a collet be used on the same machine or do different machines take collets and some take mill holders?

[acondit]

ZinSnipe,

I have both R-8 collets and R-8 endmill holders for my Grizzly.

Alan

[ZipSnipe]

do they hold the same type of cutter?

[WhiteTiger]

Yes they do. Both have round holes for holding cutting tools with round shanks. The difference is that an endmill holder has a solid nose with a hole in it and a setscrew to lock in the cutting tool.


Tiger

[OwenL]

Weldon Shank endmill holders are built to match the shank diameter of the end mill. IE: 1/4" 3/8" 1/2" 5?8" 3/4" etc etc metric shanks as well. The end mill will have a shouldered flat spot ground on the shank about mid way. This flat spot lines up with a set screw in the endmill holder. After the endmill is installed the set screw is snuged up, the end mill is then pulled DOWN against the set screw and then the screw is tightened up solid. These end mill holders will work on straght shaft tooling of a matching diameter, with out the flat spot, but there is a very minor risk of the tool slipping in the holder [minor depending on the DOC and such similar factors.]