1a thread class right-hand 0.279" thread length hexagon head style 0.062" hole diameter 20 thread quantity per inch head chromium surface treated unf thread series
2a thread class right-hand 0.560" thread length flat chamfer head style 20 thread quantity per inch shoulder undercut under head, 0.015 in. wide x 0.020 in. deep unc thread series
3a thread class right-hand 0.846" thread length flat chamfer head style 13 thread quantity per inch copper bearing surface of head surface treated unc thread series