3a nut THREAD2a stud thread thread class right-hand nut threadright-hand stud thread 0.688" nut thread thread length 3.000" overall length 20 nut THREAD14 stud thread thread quantity per inch hole in both ends 0.065-0.072 in. dia thru, csk 60 deg to 0.11 in. dia cadmium surface treated unf nut threadunc stud thread thread series