"Jim Wilkins" wrote in message
...
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.

I'm less concerned with the head being able to spin the chuck as I am my
stepper motor being able to consistently lift it with out skipping steps and
going out of calibration with my software.

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.

The tap is not a bad idea if I could find one with a 3/8 shaft. Given its
nature I'ld probably want to lock it in place with green sleeve locker and
make it permanent. I suspect this is one of those things, I'm just not
going to be able to do to my satisfaction until I already have a lathe.
LOL.