IRWIN Drill Bit Set 63137 15 Piece 1 16 to 1 2 Inch M42 Cobalt Alloy Steel (135 Degree Split Point Jobber Length Hardened Metal Index Case Tool) GFCI Tester and thick mortar layers to and thick mortar layers to prepare bare subfloors Heavy Gauge Helical Steel Flighting: Continuous flight geometry lifts displaced dirt and debris out of the hole efficiently to prevent bit binding Heavy Duty Parabolic Web: Strengthens bit core geometry to resist torsional fracturing and chatter under heavy feed pressure the heavy duty spiral flutes extract dense metal chips rapidly to eliminate heat binding in production fabrication and machinery maintenance