Drill

Patent metadata

Field	Value
Publication number	US-9511424-B2
Application number	US-201114353399-A
Country	US
Kind code	B2
Filing date	Nov 4, 2011
Priority date	Nov 4, 2011
Publication date	Dec 6, 2016
Grant date	Dec 6, 2016

Abstract

A drill including: a chip discharge flute; and a cutting edge, the cutting edge being made up of a concavely-curved cutting edge portion formed on an inner circumferential side and a convexly-curved cutting edge portion formed on an outer circumferential side, the drill further including a cross section orthogonal to an axial center 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, a flank following the cutting edge on the tip surface having an orthogonal clearance angle β formed within an angular range of 9 to 20 degrees, and a ridgeline of the cutting edge having a chamfer formed with a width CW within a range of 0.002D to 0.02D (where D is a drill diameter).

First claim

The invention claimed is:

1. A drill comprising:
a chip discharge flute opened in a tip surface; and a cutting edge formed at an intersecting portion between an inner wall surface of the chip discharge flute on a side toward a drill rotation direction and a tip flank formed on the tip surface, the cutting edge being made up of a concavely-curved cutting edge portion formed on an inner circumferential side and a convexly-curved cutting edge portion formed on an outer circumferential side, the drill further comprising:
a cross section orthogonal to an axial center 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, and a ridgeline being formed at the intersection,
the tip flank following the cutting edge on the tip surface having an orthogonal clearance angle β formed within an angular range of 9 to 20 degrees, and
a ridgeline of the cutting edge having a chamfer formed with a width CW within a range of 0.002D to 0.02D, wherein D is an outer diameter of the drill.

2. The drill of claim 1 , wherein the cross section orthogonal to the axial center has a concave amount LF of the first concave curve set to 0.01D to 0.05D relative to a reference line connecting an outer circumferential point, at which an outer circumferential surface of the drill intersects with the first convex curve, and a drill center point.

3. The drill of claim 2 , wherein a rake chamfer width LW is a distance from an intersection between a straight line orthogonal to the reference line, which passes through the intersection of the first convex curve and the first concave curve, and the reference line, to the outer circumferential point and is 0.008D to 0.06D.

4. The drill of claim 2 , wherein a rake angle is an angle between the reference line and the first convex curve at the outer circumferential point and is set to be negative.

5. The drill of claim 1 , wherein the tip surface includes a flank disposed on a rear side of the rotation direction of the cutting edge, a gash surface formed adjacently to the flank with a clearance angle larger than the flank, a thinning surface adjacent to an inner circumferential portion of another cutting edge located on the rear side of the rotation direction of the cutting edge, and a longitudinal connecting concave surface located along a boundary line between the gash surface and the thinning surface to connect the both surfaces and concaved in a width direction, and wherein the connecting concave surface has a curvature radius R within a range of 0.01D to 0.05D.

6. The drill of claim 1 , wherein the outer circumferential surface of the drill is provided with a margin having a margin width MW of 0.02D to 0.10D and a back taper of 0.10L/100 to 0.50L/100, wherein L is an axial length of the back taper.

7. The drill of claim 1 , wherein the drill has a web thickness CD of 0.15D to 0.4D.

8. The drill of claim 1 , wherein the chamfer disposed on the ridgeline of the cutting edge has a cutting edge chamfer angle γof 10 to 35 degrees.

9. The drill of claim 1 , wherein the cross section orthogonal to the axial center has the inner wall surface of the chip discharge flute on the side toward rotation direction opposite to the drill rotation direction made up of a second concave curve formed on the inner circumferential side and a second convex curve formed on the outer circumferential side adjacently to the second concave curve and reaching a heel portion, and wherein the second convex curve smoothly connects via the second concave curve to the first concave curve.

10. The drill of claim 9 , wherein when R 1 , R 2 , R 3 , and R 4 are a curvature radius of the first convex curve, a curvature radius of the first concave curve, a curvature radius of the second concave curve, and a curvature radius of the second convex curve, respectively, the drill is set to R 1 : 0.02D to 0.4D and R 2 : 0.15D to 0.5D.

11. The drill of claim 9 , 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 is 0.75≦R 3 /R 2 ≦1.25.

12. The drill of claim 1 , wherein the drill is coated at least on a tip portion surface with a hard film.

Assignees

• Takai Kazuteru
• Osg Corp

Inventors

• Takai Kazuteru

Classifications

• Y10T408/9095

  with axially extending relief channel · CPC title

• B23B2251/04

  Angles, e.g. cutting angles · CPC title

• B23B2251/18

  Configuration of the drill point · CPC title

• B23B51/02 Primary

  Twist drills · CPC title

• B23B2228/10

  Coatings · CPC title