2a thread class right-hand 0.438" thread length thumb no. 4 head style 24 thread quantity per inch ring groove 0.029 in. min., 0.032 in. max. long, dia. 0.210 in. min. 0.213 max. located 1.750 in. from end of screw passivate surface treated unc thread series
screw, cap, socket head; steel, 0.250-28, unrf-3a rh thd, 0.500 in. nom thd lg, 2.500 in. nom fastener lg; C38 min, C45 max rockwell hardness; 190000 psi min tensile strength, 170000 psi min yield strength; 0.365 in. max hd dia, 0.244 in. min, 0.250 in. max hd h, 30 degs nom chamfer angle; 0.187 in. nom w across flats
3a thread class right-hand 0.506" thread length flat countersunk head style 1.178" grip length 24 thread quantity per inch aluminum surface treated unjf thread series