[Heath] Teeny screws for Amphenol microphone connector [addendum]

[John Klingelhoeffer]

Also another note to my comment that I did not measure the TPI of the screw, not having any easy way (or maybe ANY way) to do that, is that #2 machine screws I found match the coarse 2-56 thread I saw in McMaster.  McMaster does not inventory the 2-64 fine thread screw.


However, I remembered that I had some known 2-56 machine screws in the show as well.  I took a new Amphenol connector, and tried one of the shop 2-56 screws in the hole by fingers.  There seemed to be a nice, smooth seating of the screw which would not have resulted if the screw had been the fine pitch 2-64 variant.  


Putting the threads of the original screw and the known 2-56 screw back to back also found that the pitch was identical.  


Good luck and 73



John...
WB4LNM


"One of the Hams from Heath"


-----Original Message-----
From: John Klingelhoeffer <wb4lnm at aol.com>
To: heath <heath at puck.nether.net>; ac1wye <ac1wye at gmail.com>
Sent: Wed, Nov 25, 2015 2:53 pm
Subject: Teeny screws for Amphenol microphone connector


Hi Sandy;


I took one of the connectors I have in the junque boxe, removed the screw in question, and it measures as follows:


Diameter of head:  0.153"


Total length:  0.175"


Across threads:  0.086" dia


Threaded stock length:  0.113" (approximately)


The threads are machine and not tapered, nor is the screw pointed - the end is flat.  I will note that I have NOT put it under a microscope and counted threads per inch.  It is certainly not a self-tapping or thread-cutting screw. 




When comparing this to something available at McMaster, about the closest thing is a 2-56 flat head machine screw.  That has threads that are 0.086" in diameter, and a head of 0.162".  The size 1-72 screw is markedly smaller in each dimension.  I am guessing since it is (was) manufactured by Amphenol in Chicago at the time, that it was not metric.  


A problem for easily available screws from McMaster is the length.  2-56  FH is available in 1/8", 5/32" and 3/16" length, none of which are 0.175" long.  I don't have any idea how deep the hole goes or is tapped.  Probably a bit longer than the original screw.  I guess you could try the 3/16" long, and if it will not fit, you could file the end down some to get it to 0.175" or so.  


On mine, the flat head recesses quite a bit into the connector, so the difference between 153 and 162 thousandths is probably de minimus.  May even take care of the extra length of the 3/16 screw.  


The zinc-plated steel units from McMaster have part number 
90273A050,  $2.76 per 100.  They also offer them in two varieties of stainless steel if you are going to keep the rig for three lifetimes.  The 18-8 is only about twice the price, but 316 SS is about quadruple.  Maybe you have a local model airplane shop that has them in smaller quantities, but I wouldn't hunt to long to save $2.76!  Ebay doesn't seem to be any cheaper, and has less selection.


I also have one connector in the junque boxe missing a screw, but no telling how long it will be until I use it.  I'm not sure I have any green boxes that have that mating chassis connector on them anymore.  


Have a good holiday.  Keep the green boxes glowing.


73


John...
WB4LNM


"One of the Hams from Heath"


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