Drill and method of producing machined product using the same
A drill may have a cutting tip and a holder located on a rear end portion side of the cutting tip. The cutting tip has two cutting edges located away from each other at a front end portion, two flutes respectively extending from the first cutting edge and the second cutting edge toward the rear end portion, two side surfaces respectively extending from the first flute and the second flute toward a front side in a rotation direction, and two constraining surfaces respectively extending from the first side surface and the second side surface in a tilt direction with respect to the rotation direction. The first side surface and the second side surface are asymmetric with respect to a central axis, and the first constraining surface and the second constraining surface are point symmetric with respect to the central axis in a front end view.
1. A drill, comprising:
a cutting tip; and
a holder,
the cutting tip comprising
a first cutting edge and a second cutting edge located away from each other at a front end portion of the cutting tip,
a first flute and a second flute which are respectively continuous with the first cutting edge and the second cutting edge on a front side in a rotation direction, and extend toward a rear end portion side of the cutting tip,
a first side surface and a second side surface which are respectively continuous with the first flute and the second flute on the front side in the rotation direction, and extend toward the front side in the rotation direction,
a first constraining surface and a second constraining surface which are respectively continuous with the first side surface and the second side surface on the front side in the rotation direction, and extend in a tilt direction with respect to the rotation direction, and
a bottom surface located on the rear end portion, and
the holder being located on the rear end portion side of the cutting tip, the holder comprising
a mounting surface being in contact with the bottom surface,
a first contact surface and a second contact surface being respectively located so as to face the first side surface and the second side surface, and
a first hold surface and a second hold surface being respectively in contact with the first constraining surface and the second constraining surface,
wherein the first side surface and the second side surface are asymmetric with respect to a central axis, and the first constraining surface and the second constraining surface are point symmetric with respect to the central axis in a front end view
wherein the first side surface has a concave shaped portion.
2. The drill according to claim 1 , wherein the first side surface has an outwardly protruding circular arc shape in a front end view.
3. The drill according to claim 2 , wherein the second side surface has a straight line shape in a front end view.
4. The drill according to claim 3 , wherein the second side surface is located closer to the central axis than the first side surface in a front end view.
5. The drill according to claim 1 , wherein opposite ends of the first side surface and opposite ends of the second side surface are respectively point symmetric with respect to the central axis in a front end view.
6. The drill according to claim 1 ,
wherein the cutting tip further comprises a shaft foot projecting from a middle region of the bottom surface,
wherein the holder further comprises a shaft receiving hole which is located on a middle region of the mounting surface and permits insertion of the shaft foot into the shaft receiving hole, and a through hole penetrating between an outer periphery of the holder and the shaft receiving hole, and
wherein the drill further comprises a fixing member being inserted in the through hole and being in contact with the shaft foot.
7. The drill according to claim 6 , wherein the shaft foot has a circular columnar shape whose axis is the central axis.
8. The drill according to claim 6 , wherein the shaft foot comprises a notched portion to be brought into contact with the fixing member.
9. The drill according to claim 8 , wherein the notched portion of the shaft foot and the first contact surface are located on an identical straight line passing through the central axis in a front end view.
10. The drill according to claim 6 , wherein the through hole is located closer to the first side surface than the central axis in a front end view.
11. The drill according to claim 10 , wherein at least one of the first hold surface and the second hold surface extends in a straight line shape from the outer periphery of the holder toward the central axis in a front end view.
12. The drill according to claim 1 , wherein the first cutting edge and the second cutting edge are point symmetric with respect to the central axis in a front end view.
13. The drill according to claim 1 , wherein the bottom surface has a planar shape.
14. The drill according to claim 1 , wherein the bottom surface is perpendicular to the central axis.
15. A method of producing a machined product, comprising:
rotating a drill according to claim 1 around a rotation axis;
bringing the first cutting edge and the second cutting edge of the drill being rotated into contact with a workpiece; and
separating the drill from the workpiece.