3 PN collets

i just purchased a jefferson horizontal milling machine and it requires the above size collets. i know that i can order them from hardidge but at a extreme cost when the entire machine only cost me 200.00.
if any one has one i would like know.
thanks ken kuban

ken,
As you know, if you find a lead on them, let me know too!! I have the same machine and the same dilemma. Also, send me some pics of yours if you don't mind.--Grant

If you find some 4PN collets in your travels, that's what I'm looking for. I'll let you know if I find any 3's.

I'm at the point where I'm looking at making an adaptor to fit MT2 into it (buy an MT2 sleeve and turn/grind the outside to 4PN).

Maybe there's a market for a 3PN to 3C adaptor?

Steve

Are you sure it's 3PN? 3C collets are exactly the same diameter (.650) and the threads are only two TPI different (.645x26 for 3C and .645x24 for 3PN).

Check the threads on your drawtube.

Also, the 3pn is a bit shorter (2-1/16 vs 2-11/16 for 3c).

Maybe you could make a sleeve that looks like the taper on a 3pn on one end with a 0.650 hole and an internal taper of the 3pn on the other end? Might be less work / cost than trying to find 3pn.

You would have to make a new drawtube (assuming the drawtube really is 3pn).

For the 4PN adapter, I would start with:
http://www.use-enco.com/CGI/INSRIT?PARTPG=INSRAR2&PMAKA=214-8705&PMPXNO=945794

then machine the outside (probably have to grind, as it is hardened, but I have a tool post grinder). The OD of 4PN is 1.000" and the taper, I think is 12-1/2 degrees, so not insurmountable, even for a novice like me.

Steve

I "think" the best alternative to actually finding some 3pn would be to make a collet chuck holder that would hold some small TG or ER collets.
The little Jefferson mills cannot handle big cutters by any stretch. A small collet chuck holder would be ideal, IMO.--Grant

You could start with one of these:
http://www1.mscdirect.com/CGI/NNSRIT?PMPXNO=4467450&PMT4NO=10042628
and then turn the shaft down from 0.750 to 0.650 and then make a drawbar and you'd be all set.

Would have to be done accurately, probably ground between centers.

I like the idea of the morse taper adapter, as I can get collets, end mill holders and other tooling in that size. It would also eliminate one potential source of accumulated error if I had to make a collet chuck fit, and then have have the collet chuck and collet and then an end mill holder.

4PN is bigger, so I have more options.

Steve

3 pn collets

I have over 20 3 PN collets that you may be interested in with approx. 18 different sizes (all are round )

You can use 3C collets in place of 3PN collets, but you have to change out the draw bar from 24tpi to 26tpi. The throat angle is 20 degrees for 3PN collets where 3C is 12 degrees.
Here is a picture of 3PN collet dimensions.