I posted this to the Clausing group on Yahoo, but figured I'd copy it
here for anyone who might find it useful. Someone was looking for
ER-style collets that they could use in the MT-2 quill of a Clausing 8520
mill, which uses a 3/8-16 internal drawbar thread.

------------------------
It took some digging, but I found the info on my collets. They are from
Centaur Precision Tools, Inc. in Miami. (1-800-COL-LETS)
(http://www.centaurtools.com/). The key piece is the collet
holder/chuck. They manufacture an ER-25 Collet holder with a MT-2 taper
with the internal 3/8-16 drawbar thread. It's not a regular catalog
item, but they OEM them for somebody, and they were readily available in
July 2001. The guy from the factory that told me about them was named
Greg, in case somebody denies they ever existed. They also sell collets
in a couple of accuracies, the wrench for the chuck, and even a nice
wooden box to hold all the pieces. Because the collets cover a wider
range than a normal MT-2 collet, in theory one could get an entire set
and be able to hold drill bits of any size. I've listed the pieces I got
below, with 2001 prices. They had to be ordered through a local
distributor.

#525-117 MT 2 RD25 Inch Thread collet chuck $95.00

#22125 Rd 25 E Wrench $15.50

#WBXRD25 Wooden Box RD 25 (15 collet cap.) $30.00

#250-503 1/8" collet $24.15

#250-505 3/16" collet $24.15

#250-507 1/4" collet $24.15

#250-511 3/8" collet $24.15

#250-515 1/2" collet $24.15

#250-519 5/8" collet $24.15

There are two different collet precisions, standard and high
precision. According to the catalog, the TIR for standard precision
collets below 0.394" is 0.0006". Above that, it goes up to 0.0008".
The high precision collets have half the runout. The catalog lists only
standard precision part numbers for the inch collets, but claims that
high precision ones are available. I tried to order high precision
collets for 1/4" & above, but the dealer shipped (and charged me for)
standard precision. I suspect the high precision ones are special order.

You can shop around and get collets cheaper elsewhere, but I was so
thrilled at finding some place that would sell me a chuck for my 8520, I
decided to reward them with the extra business.

The bad news is that I haven't had time to install the chuck and use it.
I got engaged, married and moved since then, and am only now getting my
shop set up again.

Doug White

Doug White wrote:

I posted this to the Clausing group on Yahoo, but figured I'd copy it
here for anyone who might find it useful. Someone was looking for
ER-style collets that they could use in the MT-2 quill of a Clausing 8520
mill, which uses a 3/8-16 internal drawbar thread.

------------------------
It took some digging, but I found the info on my collets. They are from
Centaur Precision Tools, Inc. in Miami. (1-800-COL-LETS)
(http://www.centaurtools.com/). The key piece is the collet
holder/chuck. They manufacture an ER-25 Collet holder with a MT-2 taper
with the internal 3/8-16 drawbar thread. It's not a regular catalog
item, but they OEM them for somebody, and they were readily available in
July 2001. The guy from the factory that told me about them was named
Greg, in case somebody denies they ever existed. They also sell collets
in a couple of accuracies, the wrench for the chuck, and even a nice
wooden box to hold all the pieces. Because the collets cover a wider
range than a normal MT-2 collet, in theory one could get an entire set
and be able to hold drill bits of any size. I've listed the pieces I got
below, with 2001 prices. They had to be ordered through a local
distributor.

#525-117 MT 2 RD25 Inch Thread collet chuck $95.00

#22125 Rd 25 E Wrench $15.50

#WBXRD25 Wooden Box RD 25 (15 collet cap.) $30.00

#250-503 1/8" collet $24.15

#250-505 3/16" collet $24.15

#250-507 1/4" collet $24.15

#250-511 3/8" collet $24.15

#250-515 1/2" collet $24.15

#250-519 5/8" collet $24.15

There are two different collet precisions, standard and high
precision. According to the catalog, the TIR for standard precision
collets below 0.394" is 0.0006". Above that, it goes up to 0.0008".
The high precision collets have half the runout. The catalog lists only
standard precision part numbers for the inch collets, but claims that
high precision ones are available. I tried to order high precision
collets for 1/4" & above, but the dealer shipped (and charged me for)
standard precision. I suspect the high precision ones are special order.

You can shop around and get collets cheaper elsewhere, but I was so
thrilled at finding some place that would sell me a chuck for my 8520, I
decided to reward them with the extra business.

The bad news is that I haven't had time to install the chuck and use it.
I got engaged, married and moved since then, and am only now getting my
shop set up again.

Doug White

You could forward on to the guys looking for these that they should
broaden their horizons. :-)

These MT2- ER series collet holders are pretty available from the
suppliers to the Modell Engineering trade in England.

A useful list of same can be found here.

http://easyweb.easynet.co.uk/~chrish/links.htm

Cheers
Trevor Jones