Luthier CNC

[cropwell]

I also wanted to have a Z probe which worked without a crocodile clip.

My tool tip has earth continuity, so this type of touch plate works for me.

Even though your spindle body may be earthed, that may not continue to the tool if you have ceramic bearings, so a switch type would have to be used.

Have you metered the resistance between collet and spindle body ?