[R-390] Tightening shaft connection?

[Dan Merz]

Hi,  is there a good trick to tighten the bandwidth shaft coupler if the
shaft coming out of the i.f. chassis seems a bit small.  The shaft
coupler worked ok on the 390a i.f. chassis but when I put the 390 i.f.
chassis in the 390a  radio, the shaft seems a bit small for the coupler
even when tightened down pretty tight (gap closed).  More to come on
the  successful conversion of the 390 non-a i.f. to go in the 390a,  but
I'm trying to solve this problem so I can change bandwidth without
taking the i.f. chassis out - it seems awkward to have to do that.  I
tried putting a 2 mil shim sheet on two sides of the shaft in but that
still didn't give enough purchase on the shaft.  Maybe there's a gritty
substance that would help?    thanks,  Dan.