On Dec 16, 11:53*pm, "
wrote:
Last night on my little Rockwell 21-100 mill, I was changing the radius on the underside of rifle scope base with a boring head.

As I raised the knee, there was cutting close to me, and then as I lowered the knee there was a new .001" of cutting on the mill side.

Is my vise too heavy? are the knee gibbs loose?
What is going on?

TIA

You may well do better to do your Z-axis motion with the quill rather
than the knee. Use the kne to position the work, then lock it in
place, then use the quill to make your cut.