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gearedloco
05-23-2008, 02:31 AM
There's a locating pin in the rear of the 3C collet adapter I bought to use on my Logan lathe. How long should this pin be?

I started collecting 3C collets for my Logan 10" lathe some time back. About a year and a half ago I purchased the necessary spindle adapter from one of the HSM/MW/LS advertisers. I didn't get around to trying it until a few days ago and discovered that the indexing pin is too long. It won't let the collet seat in the adapter.

I sent email to the vendor and he shipped me a new adapter with astonishing speed, requesting I return the original. The problem is that the new adapter has exactly the same problem. We're talking grossly to long, not just a teeny little bit to long. The pin is shorter, but not short enough. It would be nice to know what the correct dimension is before I contact him again.

I'll try to measure a couple of collets, but it would be nice to know the "specified" length.

I've done a fair amount of searching and, although I've found every other dimension, that one remains a mystery.

Thanks!

-bill

JCD
05-23-2008, 08:18 AM
I don't have a clue, but I do know that a lot of the less expensive off-brand collets have a shallow keyway. You might look in Machinery's handbook for collet dimensions. I just shortened the pin in adapter with a file until all collets would fit.
It's your project, this is only my opinion.
Have fun

gearedloco
05-23-2008, 03:40 PM
I don't have a clue, but I do know that a lot of the less expensive off-brand collets have a shallow keyway. You might look in Machinery's handbook for collet dimensions. I just shortened the pin in adapter with a file until all collets would fit.
It's your project, this is only my opinion.
Have fun

Thanks for your reply. I've checked several collets - some labeled simply "Germany" and others marked "Hardinge." The keyway seems consistent on all of them.

My copy of M.H. is, I think, the 20th edition. I looked in it but couldn't find the information I'm looking for.

For some reason, I had the idea the pin was hardened and never thought of taking a file to it. Duh! That may well be the most straight-forward way to take care of the problem. At worst, I could end up with a shiny file.:o

moldmonkey
05-23-2008, 09:25 PM
Sorry the collet chart on SHOPSWARF (http://shopswarf.orconhosting.net.nz/sindex.html) doesn't show depth of key way but I thought I would post this link anyway because there is a lot of good information.

piniongear
05-23-2008, 09:49 PM
This won't help you with the groove size for the pin, but this is the onlycollet size chart I have ever come across. From South Bend Lathes.........pg

http://i12.photobucket.com/albums/a214/piniongear/10K%20South%20Bend%20Lathe/ColletDimensionsMedium.jpg

moldmonkey
05-23-2008, 10:07 PM
I just looked in my hardinge catalog and they don't give it either.:confused:

lane
05-24-2008, 03:02 PM
Don`t know for sure. But went and measured some Hardinge 3c collets the key ix .125 wide by .040 deep so that leads me to think the pin in the collet adapter should stick out about .030-.035 know more you don`t want it rubbing on the bottom of the key slot. hope this is of some help

J Tiers
05-24-2008, 09:29 PM
Another option is to lose the pin.....

All it really does is make it easier to seat the collet sometimes.

But, it also offers ideal means to burr-up the threads if you are ham-handed inserting, or at worst (although not very likely) spin the adapter in the spindle, which is not good. Usually that isn't going to happen, since the part will slip first.

If you make the adapter, odds are you won't put in a pin. I didn't, and it has never caused me any trouble not having one.

oldtiffie
05-24-2008, 09:39 PM
As I understand it, the sole purpose of the pin is to stop the collet rotating in the adaptor when the draw bar is being tightened or loosened. That being the case, the size is not (too?) important.

gearedloco
05-25-2008, 01:36 AM
I took the advice and filed down the pin. Problem solved. Best of all, my file didn't get polished. When I'd finished that, I discovered that the closer I'd bought is almost 2" too long for my 10" Logan.

Since it's not clear how the threaded fitting that holds the hand wheel is joined to the closer tube, I made a spacer out of a chunk of 3/4" schedule 80 (I think:o ) plastic pipe. Not a great solution, it's what was on hand, and it works for now.

After cleaning the spindle taper with brake cleaner, paper towels, and a little WD-40 it looks pretty good. My first measurements indicate a T.I.R of about
.0005 close to the chuck. Out an inch or so it appears to be worse, but I need to play with it a bit more. I'm using a 5/16 dowel pin for measurements.

I suspect I may need to do a tad more file work on the pin. We'll see.

Thanks for all the comments and advice!