"Jim Stewart" wrote in message
news
I just finished a cast iron adapter plate that
mounts a plain-back 5C collet chuck to the 2"-8
tpi spindle of my lathe. I can easily dial in
the mounted chuck to .0005" runout, the limit
of my measuring capability.

When I remove and reinstall the chuck/adapter
plate assembly and check the runout, it varies
from .0005" to .004". It only takes a couple
of minutes to mount the indicator, loosen the
bolts and recenter the chuck, but I was hoping
for a little more repeatability.

Am I asking for too much here?

You may have made the same error I did by expecting a snug thread fit to
align a chuck. I found out that the thread was supposed to be fairly loose
and the position should be established by the spigot and its recess.

Don Young