2a thread class right-hand 0.734" thread length hexagon head style 18 thread quantity per inch navy special project zinc surface treated unc thread series
3a thread class right-hand 2.812" thread length square extended washer head style 11 thread quantity per inch ithread relief 0.182 long by 0.492 min to 0.502 max. dia. round portion above extended washer 0.500 long by 0.560 min. to 0.565 max. dia. optional center drill within head flats 1.428 min. to 1.562 long cadmium surface treated unc thread series