[R-390] Bristol Clamp Screws

[Barry Scott]

Looks like the front panel is about finished and turning my attention to
the knobs, escutcheon, and meter covers.

When I first removed the two large knobs a couple of years ago, I could
tell one of the clamp screws did not have the same spline-drive as the
other one as the socket was slightly larger than the other one.  I thought
someone had replaced the spline-drive with a hex-drive but yesterday, I
discovered that it is a larger spline socket.  Both are six-spline versions
but one is a 0.096" (Xcelite 99-66) and the other is a 0.111" (Xcelite
0.111").

>From what I can tell, they're both #4-40 screws but one is just a few
thousandths larger in diameter (not large enough to be a #5 and possibly
just manufacturing tolerance differences).

Also, one knob has the two ribs in it and the other doesn't.  I didn't
track which one had which screw in it and I don't think that really
matters.  Most likely, somewhere in a repair depot, a knob was installed
from a radio from a different manufacturer.

I'd like for these both to have the same Bristol drive (the 99-66 0.096"
version) so as to match the screws from all the other knobs.  Anyone know
where I could get a proper socket-head screw for this?  I know these are
pretty rare and likely the only place I'd find that is from another
clamp/knob/radio but thought I'd ask.

Thanks,
Barry - N4BUQ