I was just out drilling PVC pipe for a direction-finding antenna, and I've never had any
problems. But I use a high-speed twist drill rather than a spade drill. After the drill
passes through the first side of the pipe I stop, plumb the drill, and start into the far
side slowly (just as I do when starting the first side.) I've never had problems with
this - except that I never get the hole quite straight. In some cases it is actually
better to drill a separate hole from each side, but you can't always get a bolt to
fit though it properly.
But on re-reading your description, I see the difference - I rarely drill anything
larger than 1/8" in the PVC pipe or fittings. For a 13/16" hole I'd drill a pilot hole
about 1/8", then go in from each side with a larger bit. A twist drill at fairly low
speed should work, but first I'd experiment with one of the new-fangled step
bits and see if that does the job. (It might not, since the step drill is designed
for drilling flat plates.) If you drill too fast then the plastic will melt rather than
being cut, and will stick to the drill when it cools.
However, this really shouldn't matter - I wouldn't bother using such an approach
for a tape-measure yagi. I've built at least 6 or 8 of them over the years I suppose.
While the first one followed the original WB2HOL dimensions, since then I've adapted
other yagi designs to use tape measure elements with better results. The original
was designed for a sharp rear null, but I never use that when I'm hunting, so I
choose yagis for good gain and half-power beamwidth. However, if you are using
an unmodified HT without an external Offset attenuator, the null might be the only
way you can take bearings on stronger signals.
I have seen folks using 3/4" PVC pipe for the whole frame, then put the elements
THROUGH the Ts and crosses and insert small pieces of 3/4" PVC pipe to hold them
into place. (This may require filing out part of the fitting, depending on the thickness
of the tape.) My approach, however is simply to secure the elements to the outside
of the croses and Ts with fiberglass strapping tape: cheap, simple, and light-weight
compared to using hose clamps. For the driven element I use a wrap of tape plus a
sheet metal screw through the tape and into the PVC fitting on each side as it lacks
the structural integrity of the continuous element. You can't really drill the tapes,
so I punch a hole in the tape with a small nail. mark the location on the PVC, and
pre-drill a hole slightly undersized for the screw. (I used to use the screw for the
connection to the element, but that isn't very reliable over time.)
The tape also appears to overcome one of the primary causes of failure for tape
measure yagis - stress either at the screws or the hose clamps where they are
attached to the boom. The tape has enough "give" to it that it helps to keep
the stress from focusing at a sharp edge.
Actually I usually the 3/4" or 5/8" tapes from a dollar store - each is long enough
to build a 2m yagi with some extra reinforcing in the center of each element. This
is lighter and more convenient than the heavier 1" tape, and the reinforcing helps it
to snap back into shape faster.
Meanwhile, here is another method of attaching the tapes that might work for you:http://www.open-circuit.co.uk/tape.php