Collets: what's the diff...

[DSL PWR]

... between C, ER, TG,and DA collets?

[ajl6549]

The largest difference is the way the collet is closed or squeezed. Take the DA style for instance, (DA is for double angle) it uses two fairly small angled/tapered ares to squeese the collet against the tool being held. TG collets use one long taper that runs almost the entire length of the collet. ER collets are sort of a mix of a long and a short tapered area. All the collets you mentioned use a nut in front of the collet to close it except for the C style. C collets (similar to R type) are mostly used in machine spindles and attachments and they are typicaly drawn tight the back of the collet. Think of an R8 in a bridge port spindle or the C type used in many tool grinding fixtures.

[Chuck Reamer]

The holding force of different collets is also very different. Double angle collets are a thing of the past.

A TG collet will hold with much more force than an ER style collet, but the ER collets that I have used (kennametal) have up to 1mm of size range.

It depents what you need it for I have never had an ER collet have a tool suck out of it. Then again I dont really want to risk it on a mold will a lot of time and money already into it.

[Willbird]

Most makers of cutting tools I have worked with say for best tool performance it is best to use an ER collet that exactly fits the tool not a "range" collet. It is in fact easier to "feel" that the ER collet is still in good shape if you are using a size/size collet that does not need sprung open or squeezed shut to even grip the tool to start.

To evaluate a collet I was shown to run the nut tight by hand until a slight drag is felt on the tool, if the collet is still in good shape it feels much better and smoother than one where is is sprung or worn into a taper or barrel shape on the ID.

Also thought it is more work, it is better to completely break down the collet from the holder and clean the tapers on both...otherwise stuff can sort of adhere to the collet and the holder tapers because when the collet is loosened, and re-tightened it's orientation to the holder is changed so that the dirt and grit that was on the holder ID taper where the collet slits are gets pressed in between the collet and the holder when it is re-clamped.

The nut seals like Parlec makes are very nice as well for keeping crap out of the collet and holder even if you do not use thru spindle coolant.

http://www.parlec.com/images/pdf/tol__er_collet.pdf

Page 7 and page 8 are the seals I speak of

Bill

[RICHARD ZASTROW]

As willbird says, the ER collets are pretty much the standard. BUT there are differences in quality and precision. Some are refered to as "precision" grade, usually as mentioned above exact size, no range or ".005" collapse" Good quality collet suppliers will state the runout at the collet nose and some distance from the nose. My personal preference for ER collets is Rego-flex. As far as I know, they disclose to the buyer the guaranteed runout tolerance and from these specs appear to have the least runout.