[国外标准] DIN 74-2-1991 Counterbores (holes) for cheese head pan head and hexagon socket head cap screws
[国外标准] SAE J485-1998 HOLES IN BOLT AND SCREW SHANKS AND SLOTS IN NUTS FOR COTTER PINS
[国外标准] BS EN 3202-1995 holes and traps for t-head bolts. design standard this standard specifies the holes