"STEEL,O/A W 0.540 IN.,NOSE HARDENED TO 58 ROCKWELL C,A MIN. DEPTH OF 0.020 IN. W/THREE HOLES,CENTER HOLE 0.626 IN. NOMINAL DIA. THRU,THREADED HOLE 0.217 IN. THRU TAP 1/4-28 UNF THRU,COUNTERSINK 1/4 MM BY 90 DEG.,TOP HOLE 4MM THRU COUNTERSINK 6MM BY 60 DEGREE,FOR EXHAUST END"