Welcome.
I can't help with the actual size and pitch and tpi. I'm going to guess that you are referring the set screws for the hinge pins. I'm thinking that the set screws are fairly universal for flat bed machines. From my understanding there are some machines that had different size holes for the hinge pins, but I thought the set screws were the same. These would also be needed for a portable bases.
https://shop.sew-classic.com/Screw-H...?categoryId=-1 (Not affiliated with link) has a picture of the set screw and location at the back base of the machine.
Janey - Neat people never make the exciting discoveries I do.