Pete Keillor wrote in
:

On Thu, 15 May 2014 11:19:15 GMT, Doug White
wrote:

I have a small part I need to modify slightly. It is steel, but with
a polished finish, and I don't want to scratch it up. It's difficult
to tell, but it may have a very thin epoxy or some other protective
coating. It's hard (RC ~ 52), and I will be using a sharp carbide end
mill and light cuts. I only need to remove 5 to 10 mils in one area.

I don't want it to slip in the vise, and I'm wondering what's the best
way to hang onto it while protecting the finish. I could use tape,
but Scotch tape is a bit slippery, and the adhesive on masking tape is
thick enough I'm concerened it might creep. I could ue thin cardboard
shims, or maybe even aluminum, but that might mar the finish.

Comments? Recommendations?

Thanks!

Doug White

I've heard plain paper to prevent slipping. Might protect the polish
as well. I haven't tried it. Good luck.

I used this approach. It gave me a good grip, and didn't scratch the
part. That's the good news. Either the part is a lot harder than they
claimed, my carbide is softer, or (more likely), my little Clausing mill
isn't rigid enough to make small cuts in hardened material.

I haven't figured out what was flexing or slipping (the end mill in the
collet is another possibility), but the end mil barely scratched the
surface. I finally ended up grinding it down freehand with a Dremel.
It isn't as pretty as I would like, but it worked.

Sorry about the firestorm about "mills". The spare "l" was a typo on my
part. I have worked in the aerospace electronics arena since the early
70's, and was taught machining by a friend's father with a similar
background.

"Mil" is a VERY common term in microwave circuit work, electronics, and
printed circuit design. All the machinists I've talked to (in & out of
that field) in the Boston area recognize it. I also worked at HP in
silicon valley in the early 80's, and no one there had any issues with
it, so I don't think it's regional. It may be that if you do metalwork
for the electronics industry, it's a common term. I can see where large
manufacturing outfits that generally deal with bigger dimensions might
not use it as much. I just find it easier to say & type than "thou".
Verbally, "thou" works well, but when typed, I start wondering when
"thee" is going to join the fray.

Doug White