Quote Originally Posted by DIYSwede View Post
Thanks Rick for a very good walk-thru - very methodical and easy-to-follow write-up!

Apologies for probably stating some redundant and/ or undemanded info here:
The resistance contact measuring method is clever indeed, but shouldn't your entire mill be safety grounded?
I. e. The foundation and table should be grounded together with quill and chuck - and thus measure <1 Ohm.
Most chuck mount contact measuring devices I know of use this very fact to even function in the first place.

Having the quill/ chuck ungrounded developing a fault at live voltage, could mean real trouble.

Being a "concerned electrician" (amongst other duties) in a Arts Uni*, I'm on constant vigil in these aspects.

-Have fun and be safe!
Johan

*I could probably start an entire sub-forum with stories of "When Electricity meets Artist's Creative Juices"...
Saved quite a few BAs and even an odd PhD candidate from blind dates with Darwin (and Dunning-Kruger) thru the years.
"Sheer luck" is not a proper Health & Safety practice in any workplace.
Johan,

My mill is grounded. I would NEVER have it any other way.

The resistance measuring device is battery powered and floats. It is just an ohm meter except that it is measuring very small resistances.

If you measure between quill and table with a common ohm meter, you will read zero. But if you are looking with a meter that can read milliohms, it is a different story. You can read more about this subject at https://rick.sparber.org/electronics/ReadMeEEF.pdf.

Rick