[ARC5] Screw usage

[Mike Hanz]

 > There are both black and nickel #3 screws used in the ARC-5 sets. Was 
 > there any particular scheme for  selecting which was used where?

Esthetics?  :-)  That strange screw finish dichotomy (on the receivers 
especially) has always puzzled me as well, though it descends to a level 
of esoterica that can be somewhat mind numbing.  The original 
fabrication drawings for the receivers simply show ARC #6017 black oxide 
screws all around the front lip (except the bottom) and the first 3 from 
the front for the top cover on each side.  These are all 7/32" long. 
All the rest of the cover screws and bottom plate screws are specified 
as 3/16" ARC #4058s, which are nickel plated.  This is true right from 
the beginning - the very first 1939 preliminary RAT manual shows it that 
way.

Why?  Neither the drawings nor manuals give any apparent clue.  It might 
have been a desire to reduce bright reflection points when reviewed from 
the front, but then that premise is ignored with the transmitters that 
were introduced 3 years later - they use a nickel plated 1/4" throughout 
on the top and bottom covers.  The answer may be something like an 
original Navy 'anti-reflection' requirement which was eliminated on the 
ATA transmitters but never modified on the receivers - I've run into 
several cases of manufacturing inconsistencies like that in the command 
series.  Most would seem to be caused by inertia - using the same 
drawings over and over again for later products without a careful review 
of what could be changed.  There's a war on, don't ya know?

It also may be - and I'm leaning more toward this explanation lately - 
that the only finished ARC drawings available in 1939 for these 
particular length screws had the disparate finishes already specified 
for an earlier application, and the designer didn't think it worth 
stocking yet another type of the same length screw just to change the 
finish.  That would apply to the finish of the capacitor mounting screws 
as well.  Of such small decisions are such large debates later begun...

Best 73,
Mike