In article ,
Ernest Christley wrote:

Smitty Two wrote:

Anyway, I can see you like the bolts. You could make your own clamping
fixture, a combination of the V-block idea and the two by four idea. If
you have a table saw, you could cut stepped grooves in two 6 or 8 inch
long wood blocks. The inner step has a width and depth of 1/2". The
outer step has a width of 1" and a depth of 1/2." Drill some holes for
drill bushings, available at the industrial hardware store, press them
in, clamp the two halves around the three tubes, and drill.

If you're going to do all that cutting on a table saw, then just set the
blade at a 45 degree angle and run a block through twice so that it cuts
a nice V. If you use a 2x4 block, set your fence at about 2.25" from
center and you'll get a 1/2" wide V. Drill a couple holes to bolt it to
the drillpress table. It won't be a permanent tool, but it'll work
perfectly to build one bike.

A further enhancement, I welded a short piece of angle to a C clamp.
Makes holding the tube much easier.

It seems you're talking about a fixture to drill one piece of tubing at
a time, while I envisioned a fixture to drill all three pieces at once,
while clamped together. I don't have the patience to draw in ascii, and
I know my written description was somewhat lacking.

I think having access to a machine shop has made me more particular
about how things fit, probably too particular. If it were my project, I
wouldn't drill mating holes in any two pieces of anything ever, unless
they were either clamped together, or dialed off to the 0.001 on the
mill. I'll freely concede that that may be overkill for this project.