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