On Tue, 16 Jan 2018 01:52:09 +0100, Emanuel Berg
wrote:
Today there was a guy with a MTB and on the chain stay there was a
small drilled hole, maybe 5mm in diameter. The hole didn't go out on
the other side so it was just one entry point. It looked completely
undramatic to me but he insisted it reduced strength. Well, of course,
but not to a degree where the tube would fail, right? I'd estimate the
tube diameter to 2cm plus change. It was an old MTB, 90s or the
Millenium, so does that mean most likely steel and possibly aluminium?
BTW, are carbon frames like horror story glass-fiber boats in the
sense that a crack thru micro-vibrations can make steady but all but
undetectable progressions before the whole thing come crashing down?

Metal bikes joined by welding, brazing, lugs, etc., often have vent
holes drilled into the tubes near the heating site. The reason for this
is that the heat expands the air inside the tube and the vent hole gives
it a controlled place to go- instead of, say, sputtering out through the
molten brass at the joint. Usually this hole is about 1-2 mm, but some
are larger.