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

Sounds like you don't have a bandsaw. A tablesaw or chop saw (depending on cut direction)
is perfectly capable of cutting aluminum. Hack saws work too, this is aluminum.

The other day my uncle called me to tell me he stopped over and borrowed my chop saw to
put up some crow molding. I asked him how it cut, he indicated it cut fine, that is when
I told him I've been using the blade on it to cut 80/20 and other aluminum extrusions for
years. Wear ear and eye protection.

The tapping has been addressed by others.

Wes