Vic,
FWIW – I have a faint idea that this one was described in Model Engineer many years ago, perhaps in the 60's. A round cutter (e.g. a piece of broken drill bit) is inserted into the left hand end and pokes out as per the illustrations in the links above.
Other than making a couple of stainless steel handles (for a six-way turret and a rear tool post, oh and an aluminium ball on the end of the handle which I carelessly cropped off in the photograph), I hardly ever used it.
Capacity? About 50 mm max.

One extravagance was the bronze body, a left-over from another job.
The bronze body was made to be clamped in the normal (ML7) tool post.
I seem to recall making the lead screw with a 40 tpi thread. It allowed very fine adjustment.
Cheers,
Sam 
Edited By Sam Stones on 12/10/2021 20:01:28