A "test" indicator has a small dial and a small swinging arm with a small amount of travel.
A "dial" indicator has a sliding arm and a large dial and large travel. The test indicator is generally more accurate.
I use a magnetic base to attach the indicator to the table, and indicate against the head of the mill.
Turn off backlash compensation, and then jog by .001" amounts. Count the number of jogs required to get the dial to move the other way when switching directions.
-Jeff |