[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 (chair)

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.]

[ZipSnipe]

Ok I know wearing you guys out with questions and I appreciate all answers. With a endmill holder how does this fit onto a spindel the same way a collet does?

[NC Cams]

Yes, an end mill holder fits into the spindle the same as a collet and clamps in the same way.

Look at an end mill holder as a collet with fixed size/diameter hole/housing that the appropriate diameter cutter fits into. It (cutter) is held in place by a set screw or a pair of set screws.

[acondit]

ZipSnipe,

I have had an endmill held in a collet pull down into material I was cutting and ruin the job. I have never had that happen with an endmill in an endmill holder.

Alan

[phil burman]

An end mill holder fits directly in the mill spindle and the end mill then fits in the the holder and is held by a screw through the side of the holder. Hence the name end mill holder.

A collet holder fits directly in the mill, a collet fits in the holder and an end mill fits in the collet, which is specifically designed for that holder (for example an ER collet holder). The collet, which has an external taper, grips the end mill by being compressed by a retaining nut. the collet also has a series of radial slits that allow it to be compressed as it is pushed into the taper of the holder by the retaining nut.

An R8 or MT3 collet, which both have tapers, but different, fit directly into the mill spindle and also have a series of radial slits that allow it to be compressed and grip the end mill when the collet is drawn into the spindle taper by the draw bar.

There you go, clear as mud.

Try googling the following and then read, read, read.

"end mill holder"
"ER collet holder"
"R8 collet"
"MT3 collet"


Phil (chair)

Ok I know wearing you guys out with questions and I appreciate all answers. With a endmill holder how does this fit onto a spindel the same way a collet does?

[ZipSnipe]

Thanl you Gentlemen, Education has been achieved. I just wanted to make sure when I decide to purchase a mill that I get the right stuff to go with it. Once again thanx

[NC Cams]

Reply to Acondit:

Conversely, I've had the same cutter that cut quite accurately in a collet cut with chatter and a lousy finish in a holder.

Each (collet vs tool holder) has it's merits/demerits and you have to use each in the proper circumstances.

Based on the type of questions that were being posed by the noobie machinist in development, he seems to be looking for the proper items to buy to "get started".

In that regard, I'd recommend the purchase of the following in MY order of "getting started priority":

1. A mill fitted with an R8 collet.

2. A nice setof R8 collets (preferrably in 1/32" steps, or ultimately "god I wish I had 1/64" steps") - more accurate from position and runout standpoint.

"Import quality" is fine for getting started, with upgrade to Lyndex at some point later on (IF the mill he buys has a low spindle runout potential, otherwise, don't waste the mondy).

3. An R8 drill chuck for GENERAL purpose drilling/milling.

Due to the tolerance stacks arrising from the use of so many more pieces in a chuck, a chuck does tend to have a higher cutter runout potential than a collet. A drill chuck will come loose easier unless you know how to properly tighten a drill/cutter into position...

4. As needs require for hard core material removal, appropriate sized mill holders.

I use collets for most finish work and general purpose milling.

I save the mill holders for heavy stock removal.

I rarely use a drill chuck when the machine has R8 collet - had too many instances where I was unsatisfied with the results of using a drill chuck as a cutting tool holder.

Once the member takes the time to investigate and understands the definitions of the terms of the equipment he's asking about, the above reply should make sense....

[Halfnutz]

Collets generally have less runout than holders and a set is less expensive than a set of good concentric end mill holders. With a collet holder (the type with a nut) it can be easier and quicker to change tooling also. End mill holders are definately more robust as the the mill is held outside of the spindle in a substantial amount of metal with a set screw, but, like I said, a set can be quite expensive, and cheap ones are sloppy and tend to get worse as they are used. Ive heard of tooling being pulled out of a collet before, but it has never happened to me, yet.

[JRoque]

Ive heard of tooling being pulled out of a collet before, but it has never happened to me, yet.

This did happen to me once. The culprit was a using the more common metric size collets with inch type tools. I changed all of my collets to Rego-Fix brand of true inch dimension and have not seen the problem since. Mounting tools is also easier now as it requires substantially less pressure at the nut to hold the tool in place.

JR