Mini 5/16 - 18
Standard 1/2 - 13
Heavy 5/8 - 11
The grid pattern of multipurpose holes on every tooling plate and tooling block face is labelled with letters in one direction and numbers in the perpendicular direction. Tooling-block faces are numbered (counterclockwise) with Roman numerals. This allows recording the mounting-hole location of each component (e.g., A2, B3, D7, etc.) as part of permanent documentation.
Multipurpose holes are spaced within ±.0008 inches of true position on all tooling plates and blocks. The mini system is even more accurate, with all holes spaced within ±.0004 inches.