I had a chuck that didn't bottom on the spindle threads. I got an
ordinary steel washer that had a hole slightly too small to fit on the
spindle, and then I did some hand machining to get a perfect fit and to
true up the face. I used a piece of scrap wood on a faceplate, turned a
slight recess for the washer, glued it in with epoxy, and then turned with
with ordinary hss scrapers. I used a slowish speed (500 rpm?) and used 30
weight oil since I don't have any official machinist's cutting oil. The
washer was glued in solid, so I had to part it off to reverse it in a
friction fit recess to turn off the glue. I have also trued up one of my
homemade steel faceplates on the wood lathe and done some other small
scale machining when I needed a special part for something. Turning steel
on a wood lathe takes some patience and makes a mess, but it works, it
doesn't hurt your tools, and you'll be done faster than spending a lot of
time looking for some special part that might work.

-mike paulson, fort collins, co