right-hand hexagon head style 16 thread quantity per inch ream bolt fastener is locked by bending one leg of pantleg washer over the edge. unc thread series
Used on c130 aircraft. 3a thread class right-hand 0.735" thread length flat countersunk head style 20 thread quantity per inch cadmium surface treated unjf thread series
3a thread class right-hand 0.750" thread length double hexagon extended washer head style 28 thread quantity per inch bolt machine, double hex head unjf thread series