3b 2nd end thread class 4 1st end bolt hole quantity 12 2nd end thread quantity per inch flange holes threaded 4-4ounc-2b 0.25 full thd un 2nd end thread series
3a all ends thread class 14 all ends thread quantity per inch two holes drilled for lockwire 180 deg apart long w/ offset wrenching facility unjs all ends thread series
Used on aircraft, f-14a. 3a all ends thread class 20 1st end thread quantity per inch hex drilled for lockwire, 2 holes, 180.0 deg apart; weapon system essential unjf 2nd end thread series