[Collins] set screws for ring gear of 75A4 dial vernier

[Dr. Gerald N. Johnson]

I'm sure they are bristol drive. That's all Collins used. My wild guess 
is that they are 4-40 UNF but I could be wrong since I've never seen 
them or measured them. You should be able to fit a round head or pan 
4-40 screw into the threads to check. They might be as big as 6-32 or 
6-40. Fine thread bristol set screws should be available at 
www.mcmaster.com. They are a very fine source of bristol wrenches at 
very reasonable prices.

 From the picture at:
http://www.auctiva.com/hostedimages/showimage.aspx?gid=1119518&image=605701947&images=605701947,605701998&formats=0,0&format=0
I'd say 4-40 x 1/8"

73, Jerry, K0CQ, Technical Adviser to the Collins Radio Association

On 9/20/2012 2:01 PM, John King wrote:
>
>
>
> I have lost the two setscrews that hold the ring gear on the shaft of the vernier knob assembly of my 75A4.
>
> I need to know the diameter of the set screws, the thread number/pitch
> and whether the set screws are Bristol or Allen drive. Any identifying
> information available will be greatly appreciated.
>
>
> If you can, please provide me with the needed information and suggestions  from where the two set screws might be acquired.
> Thanks for your assistance. 73, John, K5PGW
>