On Mar 13, 6:32*pm, Doug White wrote:
I have a project that requires a machining operation that I am puzzling
over. *This particular piece doesn't require great precision, but I would
like to learn and practice an accurate approach to doing this.

I have an aluminum rod, 5/8" in diameter, and 3" long. *Each end will be
counterbored about 1/8" deep to a diameter of 3/8". *I want to mill a
flat bottomed groove 1/4" wide from the bottom of the counterbore to the
outside on both ends, and (here's the tricky part) I want those two
grooves aligned with each other as accurately as possible. *Basically,
there will be a flat keyhole shaped pocket in each end of the rod, and I
want the two keyholes to be vertical.

I can easily mill the groove in one end using a collet block with the rod
sticking up vertically. *The rod is too short to just flip the block
upside down and mill the opposite end with everything aligned. *If I take
the rod out of the block, I lose the alignment, and the rod is also short
enough that I can't really easily reach into the back side of the collet
block with an indicator to align the groove. *Because the groove is only
1/8" long, I'm not going to get much accuracy that way anyway.

I could mill a reference flat on the rod, but that's an extra step, and
if I'm trying to learn here, kind of cheating. *I can certainly conceive
of applications where that wouldn't be kosher.

While writing this up, it suddenly occured to me that I could probably do
both ends with the rod clamped in a Vee block. *I should have a Vee block
that is short enough to hold the rod with good access to both ends
without removing the rod between operations.

Is that the only good way? *Any other clever ideas? *Any good excuse to
buy a new tool?

Thanks!

Doug White

I'd put a 1/4" piece of keystock at the bottom of a milling machine
vise and flank it with two pieces of 3/16" keystock. Drop in the
workpiece in the vise with the 1/4" slot fitting in the middle
keystock. You should be able to clamp everything so that the
workpiece slot is parallel to the vise jaws. (Upside-down
screwdriver) Check for vertical perpendicularity with a machinist
square.