The shank is electrically conducted to the metal workpiece through the chuck and table,
the LED lights up and the beeper sounds(only for 6566-3E),
when the ball touches the workpiece
Not suitable for rotary use. Hardened shank and contact ball
Hardened shank and contact ball

Insize 4131-9D2, AMERICAN STANDARD THREAD PLUG GAGE, 9/16-18UNF, 6928640359033 