3-blade drill

Patent metadata

Field	Value
Publication number	US-9713846-B2
Application number	US-201214395877-A
Country	US
Kind code	B2
Filing date	May 30, 2012
Priority date	May 30, 2012
Publication date	Jul 25, 2017
Grant date	Jul 25, 2017

Abstract

A three-flute drill includes: three chip discharge flutes; and three cutting edges each having concavely-curved and convexly-curved cutting edge portions, an axially perpendicular cross-sectional view orthogonal to an axial center having first convex and concave curves respectively corresponding to the convexly-curved and concavely-curved cutting edge portions intersecting each other, in the axially perpendicular cross-sectional view, a concave amount of the first concave curve being within a range of 0.01D to 0.05D in terms of a drill cutting diameter relative to a reference line connecting an outer circumferential point, at which a drill outer circumferential portion intersects with the first convex curve, and the axial center, and in the axially perpendicular cross-sectional view, a rake chamfer width being a distance from an intersection between a straight line through the intersection and orthogonal to the reference line and the reference line, to the outer circumferential point, and being within 0.005D to 0.06D.

First claim

The invention claimed is:

1. A three-flute drill comprising:
three chip discharge flutes axially disposed to open in a tip portion; and
three cutting edges each formed at an intersecting portion between an inner wall surface of each of the chip discharge flutes facing in a drill rotation direction during hole drilling and a tip flank formed on the tip portion,
the cutting edge having a concavely-curved cutting edge portion in a concavely-curved shape formed on an inner circumferential side and a convexly-curved cutting edge portion in a convexly-curved shape formed on an outer circumferential side,
an axially perpendicular cross-sectional view orthogonal to an axial center O having a first convex curve corresponding to the convexly-curved cutting edge portion and a first concave curve corresponding to the concavely-curved cutting edge portion intersecting with each other at an intersection A,
in the axially perpendicular cross-sectional view, a concave amount LF of the first concave curve being within a range of 0.01D to 0.05D in terms of a drill cutting diameter D relative to a reference line K connecting an outer circumferential point B, at which a drill outer circumferential portion intersects with the first convex curve, and the axial center O, and
in the axially perpendicular cross-sectional view, a rake chamfer width LW being a distance from an intersection E to the outer circumferential point B, wherein the intersection E is an intersection between the reference line K and a straight line passing through the intersection A and orthogonal to the reference line K, and
the rake chamfer width LW being within a range of 0.005D to 0.06D in terms of the drill cutting diameter D.

2. The three-flute drill of claim 1 , wherein
in the axially perpendicular cross-sectional view, a rake angle θ is an angle between the reference line K and the first convex curve at the outer circumferential point B and is negative.

3. The three-flute drill of claim 1 , wherein
the three-flute drill has a web thickness CD within a range of 0.15D to 0.50D in terms of the drill cutting diameter D.

4. The three-flute drill of claim 1 , wherein
in the axially perpendicular cross-sectional view, an inner wall surface of the chip discharge flute facing opposite to the drill rotation direction during hole drilling is made up of a second concave curve formed on the inner circumferential side and a second convex curve formed continuously from the second concave curve on the outer circumferential side, and wherein the second convex curve reaches a heel.

5. The three-flute drill of claim 4 , wherein
when the three-flute drill has the first convex curve with a curvature radius of R 1 , the first concave curve with a curvature radius of R 2 , the second concave curve with a curvature radius of R 3 , and the second convex curve with a curvature radius of R 4 in the axially perpendicular cross-sectional view, the curvature radii R 1 to R 4 are within ranges of the following equations (1) to (4), respectively, in terms of the drill cutting diameter D:
R 1: 0.02 D to 0.4 D   (1);

R 2: 0.10 D to 0.45 D   (2);

R 3: 0.10 D to 0.45 D   (3); and

R 4: 0.3 D to 1.2 D   (4).

6. The three-flute drill of claim 5 , wherein
a relationship between the curvature radius R 2 of the first concave curve and the curvature radius R 3 of the second concave curve satisfies the following equation (5):
0.5≦ R 3/ R 2≦1.1  (5).

7. The three-flute drill of claim 1 , wherein
a tangent of the first convex curve at the intersection A and a tangent of the first concave curve at the intersection A are non-parallel to each other.

Assignees

• Itoh Kazutoyo
• Takai Kazuteru
• Osg Corp

Inventors

• Itoh Kazutoyo
• Takai Kazuteru

Classifications

• B23B2251/082

  Curved cutting edges · CPC title

• B23B51/02 Primary

  Twist drills · CPC title

• Y10T408/9097

  Spiral channel · CPC title

• B23B2251/202

  Three cutting edges · CPC title

• B23B2251/14

  Configuration of the cutting part, i.e. the main cutting edges · CPC title