Most sewing machines were made in a time before standardized screw threads came about, so many made their own. I had a Singer that was missing a screw that adjusted the stitch length and found it was the same thread as the presser foot screw but was longer. I was able to find one and it works, just doesn't look like the original as it had a different head.
Sure would like to see some pictures of your machines.
Janey - Neat people never make the exciting discoveries I do.