3a nut thread thread class right-hand nut thread 0.490" stud thread thread length 1.115" overall length 20 stud thread thread quantity per inch stud end chamfered 45.0 deg by 0.030 in. min 0.060 in.max deep, nut end chamfered 45.0 deg by 0.020 in.min 0.050 in.max deep cadmium surface treated unc stud thread thread series