6L Collet Adapter Use Identification

I recently picked up an auction lot of collets that contained some 6L collets and an adapter that happens to hold a 6L collet and I was hoping someone here may know what its purpose/use is. As can be seen by the pictures, it holds the collet with the threads exposed at the rear and does also have the key to prevent the collet from rotating. The OD of the adapter is tapered with a large OD of 1.660" and a small OD of 1.530" and the tapered section is 3.140" long.

My guess was that this would have gone in the ID taper of a spindle and then used a draw tube and hand-wheel or collet closer system. My guess is also that the large nut would have been used to assist in releasing the adapter from the taper when removing the adapter. The only part of this that doesn't seem to add up is the dimensions I have for the adapter's OD taper don't really seem to correlate to any standard tapers in the machining world that I can find. I am not sure this this adapter is a shop made item or something standard that would have came with a 6L collet system on a LeBlond lathe. The machine that I believe these collets etc. were originally with was an 18"x80 LeBlond Regal with a 1.5" spindle bore and an L1 spindle taper.

If anyone has seen anything like this and knows what it is for I would be very interested in knowing its intended use. I am also open to other ideas as to what something like this could have been used for.

Thanks,
Hunter

As I recall, L1 spindles are almost always either No. 5 Morse (small) or American Standard No. 200 (large) bore. This adapter is too small for both of those. That's not to say that LeBlond didn't choose to do some other bore on the Regal machines.

Sent from my SM-G950U using Tapatalk