You need a ring gage for calibrating it, they come with a .600" ring, something similar to this:

https://www.zoro.com/mitutoyo-ring-...zgJFEAQYAyABEgJchPD_BwE&gclsrc=aw.ds

You can replace the dial indicator with another.


Firearms imports, consignments


[Linked Image from i.imgur.com]