ME = Model Engineer Threads These come in 32,40 and 60 tpi sizes. Model Engineer nuts and bolts are rarely commercially available.
Size Outside Dia Inch Tpi Pitch Inch Core Dia Inch Thread Depth Thou Tapping Drill Size Inch Tapping Drill mm Letter Or Number
9/32 0.28 40 0.03 0.25 16 0.26 6.4 F
5/16 0.31 40 0.03 0.28 16 0.29 7.2 L
3/8 0.38 40 0.03 0.34 16 0.35 8.9 S
7/16 0.44 40 0.03 0.41 16 0.41 10.4 Z
1/2 0.50 40 0.03 0.47 16 0.47 12.0 15/32