On Fri, 18 Jun 2010 14:40:33 -0500, Ignoramus13320
wrote:

Finally I need to make something to good precision, which is to make a
mounting plate for a US Digital encoder. The spec says shaft
misalignment should be under 0.01", which means that the individual
mounting holes need to be even more precisely placed, so as the
cumulative error will stay within spec.

Anyway, step number 1 is to cut a 4x1/4"x12" aluminum flat into three
pieces. I would like to do this on a Bridgeport and to use a thin
endmill, so as to keep as much material as possible. Should I use
carbide or HSS and what speed would you recommend for, say, a 1/8"
endmill?

Second question, I will need to tap #4-40 holes in same aluminum. How
risky is this as far as tap is concerned and should I use lubrication?

i

Look at
http://www.use-enco.com/CGI/INPDFF?P...MITEM=319-6567

tap guide, 325-5179. The pin is spring-loaded and reversable, the
other end is pointed. It says for #10 thru 1" taps but I've used mine
with taps down to 00-80. I use it both at the mill and at the lathe.
I about never tap a hole without it.

For lube on ally, try Goo-Gone. I'm not kidding!