Screw Pitch Unified
Number of Blades 30
Threads per mm 4, 4.5, 5, 5.5,
6, 7, 8, 9, 10, 11, 11.5, 12,
13, 14, 15, 16, 18, 20, 22,
24, 26, 27, 28, 30, 32, 34,
36, 38, 40, 42
Accurately milled steel
blades
Designed to check
both internal and
external thread forms
Marked with nominal
size on each blade
All blades fixed in a
steel sleeve
