Not even our FAA's bible (Acceptable Methods/Techniques Handbook) is
specific, just if loose, drill to next size rivet. I'd think a few
thousandth's slop is OK. Three things strike me here about the
problem. 1) The shear force that will be applied at worst case to the
six rivets is in the hundreds of pounds range, a small fraction of
what the six "AD" type (hard) rivets can take at 38,000 PSI and
properly set; 2) CS09 needs to be chamfered to fit the bearing, so if
done neatly, the bearing housing takes some/most of the shear load; 3)
the assembly is attached to a flexible structure (cockpit module),
also diverting some of the load.
So, as non-engineering opine mindya, if worse than a few thousandth's
slop (a 9/64" drill would have given you 15), I'd just assemble it
with Redux, at the CS09 chamfer and in the rivet holes. Might want a
film of wax on CS09 to ease bearing replacement.
BTW, to deal with just-a-hair too small 1/8" holes throughout the
build, I used a miniature, hobby-store, rat tail file. Pretty well
worn by now...
Regards,
Fred F., A063
> Gidday,
> Can someone please tell me the tolerances required for safe building
> practice when it comes to drilling holes for rivets? I am sure that any
> solid rivet can only sit in a hole of a certain size i.e. too loose would be
> unacceptable. I have loose rivet holes in my CS09s that support the pitch
> torque tube laterally and elevated above the floor of the fuselage, the
> lateral triangular brackets with the snuggle plates bonded onto them. I feel
> that should I hand set these bearings to the CS09s that the spreaded rivet
> heads will swell and set OK, but that the shear load on them will be taken
> up only on the top surface of the flange that mates with the underside of
> the rivet end that has been spread. Within the cross section of the union of
> the 2 parts the rivet would be correctly loaded through the snug bearing
> holes but then be bassically unsupported within the CS09, but under a
> compressive bond from the rivet that concentrates the shear load on the
> underside of the rivet base. It all sounds a little bit complex, and maybe I
> shouldn't worry. Has anyone else worried about looseness in the mating of
> various rivetted components? Any assistance would be appreciated
> Reg
> Tony Renshaw
|