On 03/18/2012 10:02 AM, Tim Wescott wrote:
On Sat, 17 Mar 2012 13:41:59 -0700, whit3rd wrote:

On Thursday, March 15, 2012 8:54:15 AM UTC-7, Tim Wescott wrote:
How would one make nice sharp-cornered, clean-sided (I'm not sure of
the surface finish, but mirror-bright would be nice) square holes,
about 0.1" on the sides, off center from the axis of the bar (so not
square to the bar surface), in a round steel bar about 0.75" in
diameter?

Why not mill a square slot in the end of the bar, then attach a cap?
It's certainly easy to do, and the bar is big enough to take a variety
of cap-fastening schemes (weld, rivet, bolt, pin, threaded section).

Because when I'm done making the holes, I'm going to bore the bar into a
tube with 50-mil thick walls.

This could still work. Cut the bar into two pieces, on an angle, mill
your slot at the end of one piece, furnace braze the other piece onto
the one with the square slot, and hone to fit. Probably could get away
with silver solder and a propane torch to join the parts...

Bill