On Dec 21, 4:59*am, Jim Wilkins wrote:
On Dec 20, 11:08*pm, "Denis G." wrote:

On Dec 20, 4:45*pm, Jim Wilkins wrote:
The arbor screws into a 12mm x 1.0 tapped hole in the back of the
chuck.
jsw

I wonder if you could bore out that hole and tap it to mm 22 x1.5.
Then you could use the chuck in place of the ER16 collet nut. *Still
you might have problems turning the chuck. *I'm not sure how robust
the Taig mill head is.

The boss on the back of the chuck is 23mm diameter with a groove for
the snap ring that retains the scroll, the black knurled ring. The
hole is 15.8mm deep to the back of the chuck jaws. The arbor extends
14mm into the chuck.

I'd look for a 12mm-1.0 tap with a shank that fits the ER collet and
use it as the arbor. I doubt you can find or make anything as straight
and concentric as a ground tap, especially without a lathe. Tap the
lock nut, then cut the tap off short to reduce overhang.

jsw

Your solution is probably the best. I understand the difficulty of
getting the threads perfectly straight, but it's much more preferable
to have a thru hole in a lathe chuck and threading the chuck on the
spindle avoids the problems of having the chuck slip. Sherline chucks
have 3/4-16 threaded backs, which is close to the mm 22 x 1.5 size. I
found an odd fact in that both 3/4-16 and mm 22 x 1.5 are both
automotive oil filter threads. Maybe Bob could use oil filter parts
for a faceplate (although tolerences might again be an issue).