Steve Walker wrote in
:

On 3/13/2013 19:32, 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

Keyseat cutter. Square block , sticking above vise jaws, hole through
block horizontally. Set screw to lock.

If I have the right sized keyseat cutter, that would also work with the
Vee block. I'll have to check my stash of cutters. It will have to be
samll enoungh in diameter to only cut one side of the rim of the
counterbore, but that could work.

Thanks.

Doug White