Pictured below is a coupler that I designed and cast in my foundry. The design is based on the IBLS suggested design dimensions.
Finished coupler parts excluding draft springs.
Finished Couplers
Match plate pattern with finished castings. Core boxes shown in lower portion of photo used to make sand core shown in upper center of picture.
Drilling hole for pivot pin.
Milling key slot using a special two fluted made from a 13/64" drill bit. Slot is 2" deep.
Machining a coupler knuckle. Milling key latch notch and drilling hole for pivot pin.