METAL CUTTING INDEXABLE DRILL TOOL

Abstract

A metal cutting indexable drill tool includes a drill body having a boring shaft. A center drill insert is mounted at a distal end of the boring shaft. A drill flute of the boring shaft is configured to direct and form a chip from the center drill insert, wherein the drill flute has a chip forming surface at a distal end thereof. The chip forming surface is arranged at a distance from a peripheral corner of the center drill insert to a point on a curve formed by the intersection of the chip forming surface and an imaginary inscribed sphere. The radius of the imaginary inscribed sphere, defined by the peripheral corner and the distance divided with the diameter of the drill tool is equal to a chip parameter A, which is indicative of the chip diameter to boring diameter ratio, wherein A is 0.3≤A≤0.5.

Claims

1. A metal cutting indexable drill tool comprising: an elongated drill body having a boring shaft and a mount shank; a center drill insert mounted at a distal end of the boring shaft in an insert seat configured to hold the insert against a bottom of the insert seat; and a drill flute of the boring shaft configured to direct and form a chip from the center drill insert, wherein the drill flute includes a chip forming surface at a distal end of the drill flute, wherein the chip forming surface is perpendicular to the bottom of the insert seat for the center drill insert, and wherein the chip forming surface is arranged at a distance X from a peripheral corner of the center drill insert to a point on a curve, which curve is formed by the intersection of the chip forming surface and an imaginary inscribed sphere, wherein a center of the imaginary inscribed sphere coincides with a center of the distal end of the boring shaft, wherein a radius of the imaginary inscribed sphere is defined by the peripheral corner of the insert, wherein the distance X divided with a diameter of the drill tool Dc is equal to a chip parameter A, which is indicative of a chip diameter to boring diameter ratio, and wherein the chip parameter A is 0.3≤A≤0.5.

2. The metal cutting indexable drill tool according to claim 1, wherein the chip parameter A is 0.37≤A.

3. The metal cutting indexable drill tool according to claim 1, wherein the chip parameter A is A≤0.42.

4. The metal cutting indexable drill tool according to claim 1, wherein said point on the curve is on a midpoint of said curve.

5. The metal cutting indexable drill tool according to claim 1, wherein said chip forming surface extends a distance≥Dc/4 in a radial direction relative a longitudinal axis of the metal cutting drill tool, and where Dc is the diameter of the metal cutting drill tool.

6. The metal cutting indexable drill tool according to claim 1, wherein said chip forming surface is perpendicular to the bottom of the insert seat throughout its entire length.

7. The metal cutting indexable drill tool according to claim 1, wherein a radial distance d1 from a top of the insert to the chip forming surface is d1=Dc.Math.P, where P is 0.04≤P≤0.08, and Dc is said diameter of the drill tool.

8. The metal cutting indexable drill tool according to claim 1, wherein a radial distance d1 from a top of the insert to the chip forming surface is d1=Dc.Math.P, where P is 0.04≤P≤0.06, and Dc is said diameter of the drill tool.

Description

LIST OF DRAWINGS

[0017] FIG. 1 is a perspective drawing of a metal cutting indexable drill tool according to an embodiment of the present invention,

[0018] FIG. 2 is a top view of the metal cutting indexable drill tool disclosed in FIG. 1, and

[0019] FIG. 3 is a perspective view of the distal end of the boring shaft of the metal cutting indexable drill tool disclosed in FIG. 1 and FIG. 2 with an imaginary inscribed sphere.

DETAILED DESCRIPTION OF EMBODIMENTS

[0020] Reference is made to FIG. 1 which shows a metal cutting indexable drill tool 100, comprising an elongated drill body 101 having a boring shaft 102 and a mount shank 103. The metal cutting indexable drill tool further comprises a center drill insert 104 mounted at a distal end 105 of the boring shaft 102 in an insert seat 106 configured to hold the insert against a bottom of the insert seat 106, a drill flute 107 of the boring shaft 102 configured to direct and form a chip from the center drill insert 104. The drill flute 107 comprises a chip forming surface 108 at a distal end 109 of the drill flute 107. The metal cutting indexable drill tool is characterized in that the chip forming surface 108 is perpendicular to the bottom of the insert seat 106 for the center drill insert 104, and in that the chip forming surface 108 is arranged at a distance X from a peripheral corner 110 of the center drill insert 104 to a point 301 on a curve 302, as seen in FIG. 3. The curve is formed by the intersection of the chip forming surface 108 and an imaginary inscribed sphere 309. The center 303 of the imaginary inscribed sphere coincide with the center of the distal end 105 of the boring shaft 102, wherein the radius of the imaginary inscribed sphere is defined by the peripheral corner 110 of the insert 104, and wherein the distance X divided with the diameter of the drill tool Dc is equal to a chip parameter A which is indicative of the chip diameter to boring diameter ratio. The chip parameter A is 0.3≤A≤0.5.

[0021] The present inventors have realized that by having such a chip parameter A in the above interval, a favourable chip forming process is achieved and a chip with diameter X=A.Math.Dc is formed. The diameter of the formed chip is the diameter of the helical chip formed in the drilling operation, and this is an important parameter for designing a boring shaft. The diameter of the chip may be used to optimize the amount of material in the boring shaft, which means that a stronger boring shaft may be obtained. This way the boring shaft may be designed for increased strength with maintained chip control and chip evacuation.

[0022] In one embodiment, the chip parameter A is 0.37≤A. This way a chip with a diameter larger than a minimum is obtained.

[0023] In one embodiment, the chip parameter A is A≤0.42. This way a chip with a diameter smaller than a maximum is obtained.

[0024] Now with reference made to FIG. 3 again, which shows the imaginary inscribed sphere 309 arranged at the center of the distal end 105 of the boring shaft 102. The center 303 of the imaginary inscribed sphere 309 coincide with the center of the distal end 105 of the boring shaft 102. The radius of the imaginary inscribed sphere is defined by the peripheral corner 110 of the insert 104. The peripheral corner is the radially peripheral corner and axially peripheral corner relative a longitudinal axis of the drill tool 100. In other words the peripheral corner 110 is the radially outermost and axially outermost corner of the insert 104 relative the drill tool 100 and is thus the active corner of the insert which is closest to the wall of the hole which is formed when drilling. The curve 302 is formed by the intersection of the chip forming surface 108 and the imaginary inscribed sphere 309.

[0025] In FIG. 3 said point 301 on the curve 302 is on a midpoint of said curve 302. But due to the geometrical relation between the curve 302 and the peripheral corner 110, the point 301 may be placed anywhere on the curve 302 without significant impact on the length of the distance X as shown. The distance X is the shortest distance from the peripheral corner 110 to the point 301.

[0026] As illustrated in FIG. 2, said chip forming surface 108 extends a distance w≥Dc/4 in a radial direction relative a longitudinal axis of the metal cutting drill tool 100, and where Dc is the diameter of the metal cutting drill tool 100.

[0027] FIG. 2 shows that said chip forming surface 108 is perpendicular to the bottom of the insert seat 106 throughout its entire length.

[0028] FIG. 2 also shows the radial distance d1 from a top 201 of the insert 104 to the chip forming surface 108. This radial distance d1 is d1=Dc.Math.P where P is 0.04≤P≤0.08, and Dc is said diameter of the drill tool 100. This distance d1 is important for chip evacuation and P is preferably 0.04≤P≤0.06.