Ignoramus6780 wrote:

I am still struggling with making an encoder adaptor that would go
into the top of my spindle (spindle is hollow, with a 26mm hole), and
have a 3/8" shaft protruding on top to mount the encoder disk.

After a few things that did not work, I am settling on simply making
this adaptor out of 12L14. It should be easy to make on a lathe. I am
thinking how to avoid making it "expand" but just stay in place
without expanding.

Whet I would like, I think, is make it fit the spindle precisely, yet
without any significant force involved (that is, not press or
interference fit), but use some weak glue to hold it in place. This is
so that I would pull it out easily when necessary.

Would anyone have any suggestions as to the glue.

Thanks

Can you post some close-up pics of your mill head from all accessible
locations, access ports, etc? I'm pretty sure we can come up with a
better solution if we can see in detail the possible options.

I'm pretty sure that you would be better off with an inductive pickup of
a gear than messing with a shaft encoder. You don't need a lot of
resolution, and even if the gear you pickup from has different ratios in
high/low ranges, you can easily account for that on the software end.