TAP DRILL SIZES - INCH & METRIC with DRILL SIZE FORMULAS

1 TAP SIZECUTTING TAPSTRU-FLO FORMING TAPSINCHMETRICDRILL SIZEDECIMAL EQUIVALENTDRILL SIZEDECIMAL EQUIVALENT0-803 X X X X X X X X X X X X X X -165 X X -2025 0M12 X 2 0 m X 5 0 m X -1231 -18 33 / 8 -1117 -1837 X X X X 2 5 m SIZESD rill SIZES given are the closest DRILL DRILL SIZES - INCH & METRIC with DRILL size FORMULASENGINEERING DATANOMINAL SIZENPTNPTFNPSCNPSMNPSFNPSIBSPTBSPP1/16 - 27D ( )D ( ). - 27Q ( )Q ( ). - - - - - - - - - 9 31 - - 11-1 0 - - 11-1/2 - - 11-1 - - - 11-1 SIZES THREAD DRILLED HOLE SIZESTAP SIZECUTTING TAPSTRU-FLO FORMING TAPSINCHMETRICDRILL SIZEDECIMAL EQUIVALENTDRILL SIZEDECIMAL EQUIVALENT3/4 -1021 -1611 X 5 0 m X X X -949 -1413 X X X X -763 -121-3 X X 241-1/4 -71-7 9 41-1/4 -121-11/ 6 X X 3/8 -121-19 X X 61-11/ 3 X X SIZES given are the closest DRILL DRILL SIZES - INCH & METRIC with DRILL size FORMULAS (cont.)

2 ENGINEERING DATATHREADSPER INCHDOUBLETHREAD DEPTH50%THREAD55%THREAD60%THREADRECOMMEN DED RANGE80%THREAD85%THREAD65%THREAD70%THREA D75% 9 8 0 4 3 8 9 9 0 0 8 2 0 0 4 FOR TAP/ DRILL SIZES (INCH)Figures in table show amount to subtract from of screw to obtain specific percentages of thread. Select nearest size commercial stock DRILL . METHOD 1: Drilled Hole size (in.) = Basic Major Dia. Of Thread (in.) - *Use whole numbers for % of 65% (not .65). METHOD 2: Nominal - (Dbl. Thread Depth X % of Full Thread) = Drilled Hole SizeEXAMPLE: To find the hole size for obtaining 75% of thread in a 1/4-20 tapped hole, follow first column down to 20 threads, then across to 75% of thread.

3 This figure (.0485), when subtracted from the .250 diameter, is .2015, which is the required diameter of hole. See equation: .250 - .0485 = .2015To figure whether or not pitch is too coarse for diameter: (Double thread depth) X 3 = x x = the smallest diameter possible for that X % of Full Thread*# of Threads per Inch ( )TAP DRILL SIZES - INCH & METRIC with DRILL size FORMULAS (cont.)ENGINEERING DATAmmPITCHDOUBLETHREAD DEPTH50%THREAD55%THREAD60%THREADRECOMMEN DED RANGE75%THREAD80%THREAD85%THREAD65%THREA D70% .. FOR TAP/ DRILL SIZES ( METRIC )Figures in table show amount to subtract from of screw to obtain specific percentages of thread. Select nearest size commercial stock DRILL . METHOD 1: Drilled Hole size (mm) = Basic Major Dia.

4 Of Thread (mm) - *Use whole numbers for % of 65%, use 65 (not .65). METHOD 2: Nominal - (Dbl. Thread Depth X % of Full Thread) = Drilled Hole SizeEXAMPLE: To find the hole size for obtaining 75% of thread in a (M6) 6mm x tapped hole, follow first column down to threads, then across to 75% of thread. This figure (.9743), when subtracted from 6mm diameter, is , which is the required diameter of hole. See equation: M6 - ( X 75) = (6 - .9743) = figure whether or not pitch is too coarse for diameter: (Double thread depth) X 3 = x x = the smallest diameter possible for that of Full Thread* X mm DRILL SIZES - INCH & METRIC with DRILL size FORMULAS (cont.)ENGINEERING DATA