These are custom drilled socket head cap screws we supplied our customer that specializes in aerospace parts repair. They are made domestically in the USA using 17-4 PH/AMS 5643 material with AMS 2759/3, H1100 (30-37 Rc) heat treat, heavy medium sand blast, and finally passivation. The socket head is drilled in four places at 60 degrees between each pair, using a #56 drill bit at .0465" diameter. The length is set at .635-.615 inches and the 8-32 UNJC-3A threaded section is to be maintained at .510 to .490 inches.
