[Luke]

If I remember correctly, Hugh Clark posted a good description of Luger grip screw threads a couple of years ago. Possibly this thread is still available.

UPDATE: Just did a quick search and found multiple comments on grip screw threads. Two from Hugh are copied below.

1. "The grip screws apparently were made in two sizes, I don't know when, where, how or who. They were made in 3/16"x32tpi, and in 4.5mmx.8 thread pitch. I just bought the set of Luger dies and taps that Sam Buscemi had for sale. According to him the 4.5x.8 mm is a rare configuration. If any one needs their threads renewed on the frame or screws of their gun, I can do this now.

2. "Most of the grip screw threads are Whitworth 3/16x32 TPI. Some are Whitworth 4.5mmx.8 pitch. These are usually on earlier guns in random samples. The 4.5 mm screw will be a loose fit in the 3/16" hole and the 3/16" screw will bind in the 4.5 mm hole."

Good luck with your problem.

Luke