Drill and drilling method for workpiece
AssigneeSubaru Corporation
InventorsTatsuo Nakahata, Manabu Saito, Masanori Hosoi, Hideharu Takahashi
Life of this patent
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Abstract
A drill includes a cutting edge. The cutting edge has a point angle which is continuously decreased from a center-position point angle A (herein, 0°<A<180°) at a center position to a maximum-diameter-position point angle of 0° at a maximum diameter position. The cutting edge has a relief angle which is continuously decreased from the center position to the maximum diameter position. The cutting edge of the drill has a relief angle at the maximum diameter position. Hence, the cutting edge also serves as a cutting edge for reaming. The ridgeline and relief face of the cutting edge have no corner, thereby providing good wear resistance.
Claims10
A drill comprising:
- a cutting edge;
- lands formed between helical flutes;
- and
- margins at edges of the lands along the helical flutes,
- wherein the cutting edge has a point angle which is continuously decreased from a center-position point angle A at a center position to a maximum-diameter-position point angle of 0° at a maximum diameter position,
- wherein the cutting edge has a radial relief angle which is continuously decreased from the center position to the maximum diameter position,
- wherein the cutting edge has a rake angle of 0°,
- wherein a radial relief angle ε at the maximum diameter position satisfies a condition ε<15°,
- wherein the point angle A at the center position satisfies a condition 90°<A <150°,
- wherein a length of the cutting edge along an axis of the drill is at least 1.6 times a maximum diameter of the drill, and
- wherein a width of each of the margins is from 0.1 to 1.5 mm.
A drilling method for a workpiece, comprising:
- a first step of drilling a hole in the workpiece by using a drill including a cutting edge, lands formed between helical flutes, and margins at edges of the lands along the helical flutes, and by cutting the workpiece by the cutting edge at the center-position;
- and
- a second step of reaming by cutting the drilled hole formed in the first step, by the cutting edge at the maximum-diameter-position while gradually shifting from the first step,
- wherein the cutting edge has a point angle which is continuously deceased from a center-position point angle A at a center position to a maximum-diameter-position point angle of 0° at a maximum diameter position,
- wherein the cutting edge has a radial relief angle which is continuously decreased from the center position to the maximum diameter position,
- wherein the cutting edge has a rake angle of 0°,
- wherein a radial relief angle ε at the maximum diameter position satisfies a condition of ε<15°,
- wherein the point angle A at the center position satisfies a condition 90°<A<150°,
- wherein a length of the cutting edge along an axis of the drill is at least 1.6 times a maximum diameter of the drill, and
- wherein a width of each of the margins is from 0.1 to 1.5 mm.
Dependencies are inferred from the claim text.