Abstract: A method for forming a through-hole on a work material using a drill having a drill head provided with a brazed-type cutting blade helps prevent generation of a spiral mark on an inner circumferential face of the through-hole and obtains a superior appearance and high working accuracy. In forming a through-hole H on a work material W by a drill head 1A with cutting blades 3A to 3C brazed to cutting blade mounting seats 13a to 13c, a drill head provided with roundness R on a blade edge outer end portion 31a of a cutting blade 3A responsible for cutting of the outermost periphery is used as the drill head 1A.

Abstract: A method for forming a through-hole on a work material using a drill having a drill head provided with a brazed-type cutting blade helps prevent generation of a spiral mark on an inner circumferential face of the through-hole and obtains a superior appearance and high working accuracy. In forming a through-hole H on a work material W by a drill head 1A with cutting blades 3A to 3C brazed to cutting blade mounting seats 13a to 13c, a drill head provided with roundness R on a blade edge outer end portion 31a of a cutting blade 3A responsible for cutting of the outermost periphery is used as the drill head 1A.

Abstract: A gun drill in which coolant delivered to a cutting part can be discharged intensively to a cutting chip discharge groove along with the chips, damage on the inner circumference of a drilled hole or fall of machining precision due to clogging with chips can be prevented, and cutting efficiency is enhanced by reducing rotary load and long lifetime can be attained. Coolant supply paths (10, 20) are provided in a tool shank (1) and a cutting head (2), one cutting chip discharge groove (3) is provided in the outer circumferential surface from the proximal side of the tool shank (1) to the distal end of the cutting head (2), discharge ports (22a, 22b) communicating with coolant delivery ports (21a, 21b) and a cutting chip discharge groove (3) are provided in the distal end face (2c) of the cutting head (2), and annular protrusions (4a) are formed in the outer circumferential surface of the cutting head (2) continuously over the entire circumference while bridging over the cutting chip discharge groove (3).

Abstract: A deep hole cutter for a gun drill system includes a tool shank and a cutting head with two or more cutting edges. The tool shank and the cutting head are separate members connected strongly by threads. The shavings produced by the cutting edges can be discharged together with the coolant supplied through the hole cutter. The shaving dischargeability is improved for higher cutting efficiency. The tool shank 1 has one outer axial discharge groove 3. The cutting head 2 has one outer axial discharge groove 6 in linear alignment with the discharge groove 3. The cutting head 2 also has a discharge port 7a formed in its front end. The cutting head 2 further has a bypass passage 7 formed in it and extending between the discharge port 7a and the discharge groove 6. The cutting edges 9a and 9c face the discharge groove 6. The cutting edge 9b faces the discharge port 7a.