15. Bored hole size before tapping ( for thread cutting ) Production data ■■Afomr eArmicaenricSatannSdtarnddPairpdePTiphreeTahdreaUdnit : mm unit: mm unit: mm NominaSl iszizee MinorTdaipamDeritlel rSoizfeinternal threads Bored hole size Size Minor diameter of internal threads Bored hole size Max. Min. ( ref.) Max. Min. ( ref.) NPSC 1/8 - 27 8.813 8.636 8.77 NPSM 1/8 - 27 9.246 9.094 9.21 NPSC 1/4 - 18 11.592 11.329 11.53 NPSM 1/4 - 18 12.217 11.888 12.13 NPSC 3/8 - 18 14.919 14.656 14.85 NPSM 3/8 - 18 15.554 15.317 15.49 NPSC 1/2 - 14 18.501 18.161 18.4 NPSM 1/2 - 14 19.278 18.974 19.2 NPSC 3/4 - 14 23.835 23.495 23.7 NPSM 3/4 - 14 24.638 24.334 24.5 NPSC 1 - 11.5 29.903 29.490 29.8 NPSM 1 - 11.5 30.759 30.506 30.7 The drill sizes are according to ANSI/ASME B1.20.1-1983 PIPE THREADS, GENERAL PURPOSE (INCH) (partial listing). ■■DforyrsDearlyAsmeearlicAamn SetraincdaanrdSPtaipnedTahrrdeaPdipe Thread unit: mm Unit : mm Size MinorTdaipamDeritlel rSoizfeinternal threads Bored hole size Nominal size Max. Min. ( ref.) NPSF 1/8 - 27 8.740 8.652 8.72 NPSF 1/4 - 18 11.363 11.232 11.33 NPSF 3/8 - 18 14.803 14.672 14.77 NPSF 1/2 - 14 18.288 18.118 18.2 NPSF 3/4 - 14 23.634 23.465 23.5 NPSF 1 - 11.5 29.669 29.464 29.6 The drill sizes are according to ANSI B1.20.3-1976 Dryseal Pipe Threads (Inch) (partial listing). Technical Information Technical-41 812