DRILL MAIN BODY FOR CUTTING EDGE REPLACEABLE DRILL AND CUTTING EDGE REPLACEABLE DRILL

摘要

This drill main body for a cutting edge replaceable drill has a chip discharge groove (8) provided with: a tip-side twisted part (8a); a base end-side twisted part (8b) having a twist angle smaller than the twist angle (θ) of the tip-side twisted part (8a); and an intermediate twisted part (8c) disposed between the tip-side twisted part (8a) and the base end-side twisted part (8b). A coolant hole (10) is provided with a first coolant hole (11) and a second coolant hole (12). The first coolant hole (11) opens to a base end surface (9) of the drill main body (2) or to a recessed portion formed in the base end surface (9) and extends, as approaching the tip side in the axial line (O), in a straight line-shape so as to face the drill rotating direction. The second coolant hole (12) is connected to the tip portion of the first coolant hole (11), extends in a straight line-shape toward the tip side of the drill main body (2) from the tip portion in a direction other than the extension direction of the first coolant hole (11), and opens into the chip discharge groove (8) at a position closer to the tip side than is the tip position of the base end-side twisted part (8b).