* Values are calculated for Length of engagement of 5xPitch. For calculations of different engagement length use the Thread Calculator Once you know your wire diameter, you need to find out what is the premissable Measurement for your pitch diameter. It is mostly used when a manufacturer does not have a Go/Nogo gauge for a thread. Drill sizes shown for steel, plastic and magnesium are such as to allow for material contraction in softer materials and to provide increased tap life. This variance does not cause any issues in most applications. Imperial UN: (Imperial Unified National thread form) A standard that describes the shape of an internal or external thread using imperial inch dimensions. Recommended tap drill sizes may vary slightly from recommended minor diameter limits to enable use of standard stock drill sizes. (UNR Only) 0.5113 (Ref) 12.987 (Ref) α Varation of 30° anngle (+/-) 1.25 (Ref) 31.75 (Ref) P Varation of pitch (+/-) 0.0011 (Ref) 0.028 (Ref) OverWire is a measuring method to obatin the pitch diameter of threads. Glossary TDS: (Tap drill size) The size of the hole that must be drilled before a tapping operation. A tapping guide for selecting tap drill sizes and proper pitch diameters. * Permisable values for thread Class 2A # Description Value (Inch) Value (mm) es Allowance 0.0011 (Ref) 0.028 (Ref) d Major Diameter 0.5537 - 0.5609 14.064 - 14.247 d 2 Pitch Diameter 0.5301 - 0.5338 13.465 - 13.559 d 3 Minor Diameter Tapping Guide Tap Drill and Pitch Diameter Limits Vol.

Form tap drill sizes