* Values are calculated for Length of engagement of 5xPitch. * Permisable values for thread Class 3A # Description Value (Inch) Value (mm) es Allowance 0 (Ref) 0 (Ref) d Major Diameter 0.7419 - 0.75 18.844 - 19.05 d 2 Pitch Diameter 0.7144 - 0.7175 18.146 - 18.225 d 3 Minor Diameter

Do not use these values for standard metric external thread design. These thread sizes and classes represent bolts and screws, as well, as other standard internal threads. For calculations of different engagement length use the Thread Calculator TAP DRILL SIZES FOR FORMING TAPS INCH Tap Size Drill Size Decimal Equivalent Percentage of Thread 0-80 1.35 mm 0.0531 75 1-64 1.65 mm 0.0650 75 1-72 1. The following table chart are standard metric internal thread sizes M 9 - M 24 per.

Imperial UN: (Imperial Unified National thread form) A standard that describes the shape of an internal or external thread using imperial inch dimensions. For example, the tap drill for 3/8-16 is 5/16. M6 x 1 6 - 1 5mm and you thought metric was difficult -) Thanks to Jay Steinbuchel of Barksdale Control Products for the following: This works for all 75 threads, not just metric. * Permisable values for thread Class 2A # Description Value (Inch) Value (mm) es Allowance 0.0012 (Ref) 0.03 (Ref) d Major Diameter 0.7407 - 0.7488 18.814 - 19.02 d 2 Pitch Diameter 0.7122 - 0.7163 18.09 - 18.194 d 3 Minor Diameter Glossary TDS: (Tap drill size) The size of the hole that must be drilled before a tapping operation. Diameter of thread minus the pitch equals the tap drill size.

Form tap drill sizes