[R-390] R-390a shaft collar/clamp 4-40 spline screws

[Chris Farley]

Hi All, 


One of my many projects has hit a dead end.  As we all well know, the Bristol (or Bristo) spline screws used on these radios are often buggered up from people in the past trying to mess around without the proper spline driver.  For restoration, it would be VERY nice to have the option of replacing 
these screws.  

There is a person on eBay selling custom made replacement knob set screws, so at least for now there is a source for those.  The RF deck slug adjustment screws should never see any kind of torque, so they are relatively safe from damage.  The screws used in the RF deck geartrain and elsewhere aren't so lucky.  

One of the RF geartrain shaft collar/clamp screws is a 4-40" x 9/16 cap screw with the .096" 6 fluted spline drive.  There is also a 1/2" long 4-40, and a 3/8" long 3-56 used on different clamps.  Unfortunately, the standard available spline drive size for a #4 cap screw is .111", not .096".  The original .096-6 screws were a custom item so that all hardware in the unit used the same size tool.  

Yes one could obviously use the standard available .111 drive screws or even plain hex cap screws for replacement in a pinch, but again it would be preferable to replace them with the correct screw.  I'm just trying to make a final 
determination re: availability of the actual, correct ones.  

I have searched, and cannot find one single source for these screws.  I have only located one manufacturer (so far) who is willing to make them-  and the quoted SS 9/16" long example is scary.  1000 pieces for $2.25/ea, 3000 pieces for $1.10/ea, or 5000 for $.80/ea.  Any way you twist it, this just isn't a cost effective option- at least not for me.  


I FINALLY found old Stewart Warner Electronics part numbers for the originals, they and their corresponding descriptions are as follows: 


035111319-213
Drawing number SM-D-343600-5 "PART SHALL BE 1/2LG, 4-40 NC-2A, FINISH, M262AOR M264A PER SPEC MIL-F-14072" ASA B 18.3


035111319-386
Drawing number SM-D-343600-6 "PART SHALL BE 9/16LG, 4-40 NC-2A, FINISH, M262AOR M264A PER SPEC MIL-F-14072" ASA B 18.3


Google turns up NOTHING for these numbers, and the original Stewart Warner Electronics company is long gone for any hope of them turning up something.  Does anybody on the list have paperwork or resources to find out if there are any additional records, SWE number cross references, Collins part numbers, FSN or NSN numbers, _anything_ that might uncover availability of NOS surplus stock of these screws (and potentially other old SWE part numbers for these RF decks) someplace?  

Any information you can share would be appreciated, as efforts towards this search will benefit us all.  


Regards, 

Chris kc9ieq