School me on collets for the Atlas lathe, 3c, 3at,or both?

Following along here....

I have a 12" Craftsman lathe and the milling attachment, but no mill cutters. Seeking info on what collet type to settle on as well. Not making any chips yet or any specific project.
 
Well, as stated earlier, you don't need both 3AT and 3C. They are not interchangeable but they have the same capabilities and limitations. If you just want the collets to hold milling cutters, probably the cheapest option is 3MT collets and a 3/8-16 Draw bar. So what do you need to be able to do?
 
Do the ER collets center as well as the 3MT/3AT/3C collets center? I assume that the ER chuck locates on the OD of the collar behind the spindle threads and sits on the flat bottom of that annular surface. It seems to me that this might not be as accurate as the spindle's MT3 socket.
 
Speaking of just what I see available tonight on eBay, the back plate centers up on the register area, which is the unthreaded area between the threads and the flange plus the front flange surface. The back plates are sold oversize on the front part of the OD. You machine the OD down so that it runs concentric to the spindle axis. So it centers up like any of your chucks do. I suppose that it could be off a little as there would be two surfaces involved with the 3MT collet (taper in the spindle and taper on the collet) four with 3AT or 3C and six with the ER. But I would expect that you would have some difficulty measuring the difference. In other words, I really wouldn't worry about it.
 
I will add that the ideal ER collet chuck would be made in two pieces. The body, which holds the collet and which attaches directly to the spindle (in the case of ones for the Atlas lathes and some others this would be threaded). And the nut. The reason that it's the ideal design is that the stick-out from the spindle nose is minimized. However, although the nuts for some if not all ER collet families can be bought, I don't know of anyone making those for sale.
 
wa5cab said:
Well, as stated earlier, you don't need both 3AT and 3C. They are not interchangeable but they have the same capabilities and limitations. If you just want the collets to hold milling cutters, probably the cheapest option is 3MT collets and a 3/8-16 Draw bar. So what do you need to be able to do?
Click to expand...

Robert I am not sure just yet on where I will be going with this hobby. That said, I know I will need collets to hold milling cutters. I just am looking to make the most informed purchase of a collet that will cover the most bases.

I would like to see a sketch of your "ideal ER collect chuck"
 
If I were just going to use the collets for holding milling cutters I would go with the simple MT3 collet that accommodates the cutter shank and the draw bar as suggested. That way you get the minimum overhang, and probably the lowest cost.

David
 
David,

Someone on another list a couple of days ago mentioned having plans (assume he meant drawings) of an ER collet chuck. I just asked him where he found the plans. If he responds and I obtain a copy, I'll put it into Files and let you know. But basically, it would be a hollow cylinder that screws onto the spindle threads. It would be threaded at the open end for the clamping nut, which I'm told can be bought. Probably two pin spanner holes in the middle. With the nut in place, the inside would be a hollow cylinder with tapered ends.
 
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