IRWIN 18"" POWER SHIP AUGER BITS WITH SCREW POINT In 18"" lengths to make holes straight and true in heavy timbers. Heavy duty special bit steel with machine-ground flutes and polished edges for smooth, wobble-free boring. Feed screw pilot draws bit into wood. Full length is heat treated and tempered. Deep, open-throat design clears chips well. Shanks are 7/16"" hex to fit 1/2"" and larger three-jaw chucks. Head and twist are ground to correct clearance for easy removal from hole.