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

3M 19078, E-A-R E-Z-Fit Probed Test Plugs 393-2005-50, 50 EA/Case, 7000127699 