I'm making a rack out of several ~ 9" long sections of 2 1/2" PVC pipe.
Each section of pipe is cut square on the bottom, and at a 45 degree
angle on the top end. The idea is to fasten them to a pair of horizontal
rails, using a through bolt on the bottom (which will prevent the objects
from falling out), and a short bolt through the back of the top wall with
the angle cut sloping forward & down. I have the tubes all cut, and now
I need to drill them.

The thing I'm pondering is how to best align the slopes so that I can
drill the holes on my mill. I can clamp the tubes horizontally using a
V-jaw in my vise, but I'd like to come up with a repeatable way of making
sure the holes are "square" to the sloping section. I need to make sure
the two holes in each tube are parallel to mate well with the rails. IF
I could be assured of repeatable rotational alignment, I could drill all
the holes in the square ends, and then all the holes in the beveled end.
This would be a lot faster than clamping each piece & cranking back &
forth 8 inches to drill both holes without removing each piece from the
vise.

The best idea I've come up with so far is to clamp a rod horizontally at
the approximate height of the middle of the tube. If the rod is square
to the mill, the rod can serve as a "stop" to push the tube against, and
it should force the slope to rotate & align correctly. I have one of
these that I could use:

http://www.use-enco.com/CGI/INSRIT?PMAKA=TN337-9322

My only concern is if it's rigid enough & getting it aligned in the first
place.

I have a gut feeling that there ought to be a better way, either simpler
or more accurate, but I'm damned if I can think of one.

Any ideas?

Thanks!

Doug White