Jon,

Hmmmmmmm. I had to stop and think about this for a bit. I routinely use a 30000 rev handheld for sculpting aluminum (JIS H 4100). At first thought you think "hey if can do it manually at 30000 than why can't a machine do it slowly at 40000?" ---but-- when I visualized the motion I make with the tool its probably very high rate strokes indeed although I doubt it would approach 100ipm. I think based on his previous posts Whelen is wanting an precision engraving/relief sculpting rig. Much the same as I am trying to figure out. I would assume he will be using tiny ball mill ends with 1/8th collet and not taking more than a few 1000ths at a time with thousands of passes thus chipload and feedrate would not be such a problem although maybe not in theory optimal for CNC in a machinist's context. As I'm new to CNC I think I'm missing something here though so anything you might have to add would be highly appreciated - I'm looking for a tool similar to Whelen's though with more workspace.

--TC