Dave
I have 2 Hit30's that run Siemans 840D. Both were bought used.When I went to for a pre-buy inspection on the older one(1999),I noticed that the switch on the spindle was replaced.Part# 6FX2001-8AA05 R6/B3126M.The shop foreman told me that they were having trouble with rigid tapping.I assume that since this switch sits atop a toothed reluctor ring,It must have something to do with position.Hope this info can help you.Also try siemans
https://support.automation.siemens.c...p6mcvepEO6rLYX
Ted