[R-390] R390 knob set screw

[Dan Merz]

Hi,  I ran into a minor problem.  The set screw in one of the larger knobs
(on the ant trim on R390) doesn't want to tighten against the shaft and I
see that the threads in the knob are damaged in the area near the shaft and
the screw likes to just ratchet back at the critical point of tightening.
It's the knob not the set screw that's the problem.  I think a longer set
screw of 3/8 length would solve the problem.  What is the thread size/pitch
on these set screws? I make it to be 8-36, an unusual size these days.   Are
there some screws longer than the standard 1/4 inch length in somebody's
pile?  The other alternative is to drill and tap it for the next larger size
set screw but who wants one knob to have a different size wrench, hi?  I
guess I could shove a piece of solder or piece of plastic in front of the
short one and hope for the best.  The trimmer shaft looks like phenolic so
I'd like to treat it nicely.  Any advice on fix appreciated,  more later,
Dan.