JP2002126923A - Drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce the generation of a friction heat due to contact of a margin with the inner wall surface of a drilled hole, and the increase of wear and cutting torque. SOLUTION: Only a given remaining size t2 being less than 2/3 of a margin width t1 within a range of 0.1-0.5 mm is left on the leading edge 26 side of a margin 20. A recess 30 smoothly inclining at clearance angle θ of 20 deg. is formed on the opposite side to the leading edge 26. A contact area between the margin 20 and the inner wall surface of the drilled hole is decreased as the occurrence of a defect is prevented by maintaining the strength of the margin 20 and by relieving the increase of cutting torque due to friction, cutting quality is improved, and the decrease of a tool life due to a friction heat and wear is suppressed.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill and, more particularly, to a technique for reducing the generation and wear of frictional heat and an increase in cutting torque due to contact between a margin and an inner wall surface of a hole to be machined. .

[0002]

2. Description of the Related Art A cutting edge is provided at an axial end, and a groove is provided in an axial direction. By being rotated around an axis, cutting is performed by the cutting edge at the end and chips are discharged through the groove. Drills are frequently used as drilling tools. In such a drill, a margin is provided along the groove, and the margin has a diameter substantially equal to the outer diameter of the cutting edge, and the diameter gradually decreases toward the shank side by a predetermined back taper. It is usually said that.

[0003]

However, in such a drill, the cutting torque increases due to the contact between the margin and the inner wall surface of the hole to be cut, resulting in loss of sharpness, generation of frictional heat and the like. There is a problem that the tool life (the number of processed holes until re-grinding) is reduced due to the outer peripheral wear of the margin. If the margin width is reduced, the contact area is reduced and cutting torque and frictional heat are reduced, but the strength of the margin is reduced and cracks occur from the base of the boundary with the second cut surface and chipping occurs. It will be easier.

The present invention has been made in view of the above circumstances, and has as its object to generate frictional heat and wear due to contact between a margin and an inner wall surface of a hole to be cut, and to increase cutting torque. And so on.

[0005]

According to a first aspect of the present invention, there is provided a drill in which a margin is provided along a groove, wherein the margin has a cross section perpendicular to an axis. 0.1mm on the leading edge side
To 0.5 mm (0.1 mm or more, 0.5 mm or less), leaving a predetermined remaining dimension t ₂ in the range of escape smoothly inclined is provided toward the opposite side of the rear end and its leading edge It is characterized by the following.

A second invention provides a drill according to the first invention,
The remaining dimensions t ₂ is equal to or less than 2/3 of the margin width t ₁ of the margin.

According to a third aspect, in the drill according to the first or second aspect, the clearance angle θ of the clearance in the cross section is provided.
Is not more than 20 °, and a predetermined step is left between the rear end of the margin and the second cut surface.

[0008]

In according to the present invention such drill, leaving only the dimension t ₂ predetermined leaving the scope of 0.1mm~0.5mm the leading edge side of the margin, toward the opposite side of the rear end and its leading edge Escapes that are smoothly inclined reduce the contact area between the margin and the inner wall surface of the hole while maintaining the strength of the margin to prevent chipping, and increase the cutting torque due to the friction. Is reduced and the sharpness is improved, and a reduction in tool life due to frictional heat, wear, and the like is suppressed.

In the second aspect, the remaining dimension t ₂ is not more than ／ of the margin width t ₁ , so that the friction reducing effect due to the escape can be sufficiently enjoyed. Further, in the third aspect, the clearance angle θ of the clearance is 20 ° or less, and a predetermined step remains between the rear end of the margin and the second cut surface, so that the strength of the margin can be sufficiently secured. The effect of friction reduction due to escape can be enjoyed.

[0010]

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a twist drill in which a groove is twisted around an axis, a straight-edged drill in which a groove is parallel to the axis, a drill having one, two, or three or more grooves. The present invention is applicable to various drills having a margin along a groove, such as a double margin drill having two margins on one land. Further, the present invention is suitably applied to a super hard tool material drill such as a super hard drill, but can be applied to a drill of various tool materials such as a high speed steel drill.

The shape of the relief is smooth from the outer peripheral surface of the margin, such as a flat shape that is straight in a cross section perpendicular to the axis, a cone-cave shape that is concave toward the axis, and an eccentric shape that is convex toward the outer side. A variety of shapes are possible, which are inclined at different angles. "Smoothly inclined" means that there is no step between the outer peripheral surface of the margin and the escape,
It varies depending on the size and escape of shape dimension t ₂ leaving for margin widths t _1, but for example, it is sufficient relief angle θ is less than about 45 °, angle relief as in the third invention θ is 20 °
It is desirable that:

In addition, such relief processing can be performed in the same manner as the secondary grinding of an outer peripheral blade such as a milling cutter. In the case of a twist drill, for example, the grinding wheel is moved along the margin while pressing the grinding wheel against the margin. As described above, the grinding can be performed by relatively moving the grinding wheels and the drill in the drill axis direction and around the axis. However, it suffices that a margin having escape is provided as a result, and the processing method is appropriately determined.

The relief can be provided over the entire length of the margin. However, when the back taper is provided, the relief is particularly provided only at a part of the tool tip side where friction with the inner wall surface of the hole to be machined is large. It is not always necessary to provide the escape over the entire length of the margin, for example, a relief may be provided. It is also possible to eliminate the escape gradually increasing the size t ₂ left toward the shank, the condition of the remaining dimensions t ₂ does not need to necessarily satisfy across the relief, at least the cutting edge is provided It is only necessary to be satisfied with a part including the vicinity of the tool tip.

The remaining dimension t ₂ is 0.1 mm to 0.5 mm
, But more preferably within the range of 0.1 mm to 0.3 mm. If the remaining dimension t ₂ is less than 0.1 mm, chipping or chipping is likely to occur in the leading edge, and if it is greater than 0.5 mm, the margin width t
_{Although it} depends on the size of ₁ , it is difficult to obtain a sufficient friction reducing effect. When the clearance is provided as in the present invention, strictly speaking, the remaining dimension t ₂ corresponds to the margin width, and the margin within the range of the remaining dimension t ₂ is a margin. Margin, margin width t ₁
Has been stipulated.

The margin width t ₁ can be set as appropriate. For example, the margin width t ₁ is set within a range of about 0.1 D to 0.2 D with respect to the drill diameter D. Also, double-dip up depth C, that the depth from the outer periphery to the double-dip up surface of the drill can also be set appropriately, for example, 0.2t ₁ ~0.5t ₁ about relative margin width t ₁ Is set within the range.

In the second invention, the remaining dimension t ₂ is equal to the margin width t.
_In the third invention, the clearance angle θ of the clearance is 20 or less.
° or less, but when implementing the first invention, the remaining dimension t ₂ may be larger than ／ of the margin width t ₁ , or the clearance angle θ of the clearance may be larger than 20 °. Dimension t ₂ leaves is set, for example, in the range of about 1 / 6-2 / 3 of the margin width t _1. The clearance angle θ may be at least larger than 0 °, but is preferably in the range of 10 ° to 20 ° in order to obtain a sufficient friction reducing effect while maintaining a predetermined strength.

In the third invention, a predetermined step remains between the rear end of the margin and the second cut surface. However, in other embodiments, it is not always necessary to leave the step positively.
For example, the relief may be smoothly connected to the second cutting surface so that the step is eliminated.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIGS. 1A and 1B are views showing a drill 10 according to an embodiment of the present invention, wherein FIG. 1A is a front view as viewed from a direction perpendicular to an axis, and FIG. 1B is a vicinity of a tip provided with a cutting edge 12. Is an enlarged bottom view as viewed from the front end side where cutting edges 12 are provided. The drill 10 is a two-blade cemented carbide twist drill made of cemented carbide, and is provided with a shank 14 and a groove 16 integrally in the axial direction. The groove 16 has an axis O (FIG. 2). ), A pair of grooves 18 twisted clockwise is formed, and a margin 20 is provided along the grooves 18. Also,
A cutting edge 12 is provided at the tip of each of the pair of grooves 18. The hole is cut by the cutting edge 12 by being driven to rotate clockwise around the axis O as viewed from the shank 14 side. The shank 14 through the groove 18
Discharged to the side. The drill 10 is provided with a pair of oil holes 22 extending vertically in the axial direction and opening in the flank of the cutting edge 12, so that a cutting oil or air can be supplied to the cutting portion as necessary. It has become.

FIG. 2A is an enlarged view of the vicinity of the margin 20 in the II-II cross section of FIG. 1A, that is, a cross section perpendicular to the axis O, and is divided by the groove 18. Direction of cutting of the land 24 (the axis O in FIG. 2 (a))
Leading edge 2 which is the edge on the left-hand side of
6, a margin 20 is provided.
Following 0, a second cutting surface 28 is provided with a constant diameter. The outer diameter of the margin 20 is substantially the same as the drill diameter (the outer diameter of the cutting edge 12) D, but is gradually reduced toward the shank 14 by a predetermined back taper.

In the state of FIG. 2A, the margin 20 is 0.1 mm to 0.2 mm on the leading edge 26 side.
Leaving a predetermined remaining dimension t ₂ in the range of 5 mm, relief 30 is provided to smoothly inclined toward the opposite side of the rear end and its leading edge 26. Escape 30
Is a flat shape which is straight in a cross section perpendicular to the axis O as shown in FIG. 2 (a) in this embodiment, but an eccentric shape which is convex toward the outer peripheral side as shown in FIG. As shown in FIG. 6, a cone-cave shape recessed toward the axis O may be adopted. Such an escape 30
Can be carried out in the same manner as the second grinding of the outer peripheral blade such as a milling cutter.
The tool tip provided with the cutting edge 12 can be machined by relatively moving the grinding wheels and the drill 10 in the drill axis direction and around the axis O so as to move along the margin 20 while pressing against the zero. It is provided over substantially the entire length of the margin 20 including the vicinity of the portion. A predetermined step is left at the boundary between the rear end of the margin 20 and the second cutting surface 28.

A specific example of the dimensions of each part of the drill 10 is as follows. When the drill diameter D (the outer diameter of the cutting edge 12) is 6 mm, for example, the remaining dimension t ₂ is about 0.2 mm.
(0.18 mm to 0.22 mm), and the clearance angle θ of the clearance 30 is 14 ° to 16 °. Further, in FIG. 2 (b) is a diagram showing a sectional shape of the front margin 20 to provide a clearance 30, the margin width t ₁ is about 1.2mm (1.15mm~
1.25 mm), and the second retrieving depth C slightly changes at the axial position due to the back taper, but is about 0.4 mm (0.3 mm).
7 mm to 0.43 mm). Escape 30 is the cutting edge 1
The margin 20 including the vicinity of the tool tip where 2 is provided
Are provided over substantially the entire length, and the entire range satisfies the above numerical values. It should be noted that the dimensions of each part in the drawings are not necessarily shown with exact dimensions and ratios.

In the drill 10 according to the present embodiment, 0.1 mm is set on the leading edge 26 side of the margin 20.
A relief 30 that is smoothly inclined toward the rear end opposite to the leading edge 26 while leaving a predetermined remaining dimension t ₂ within the range of 0.5 mm to 0.5 mm, specifically, t ₂ ≒ 0.2 mm. As a result, the contact area between the margin 20 and the inner wall surface of the hole to be machined is reduced while maintaining the strength of the margin 20 to prevent chipping, and an increase in cutting torque due to friction of the margin 20 is reduced. The sharpness is improved, and a decrease in tool life due to frictional heat, wear, and the like is suppressed.

In particular, in this embodiment, the remaining dimension t ₂ (≒ 0.
2 mm) is not more than ／ of the margin width t ₁ (≒ 1.2 mm), so that the friction reducing effect of the relief 30 can be sufficiently enjoyed. In addition, the clearance angle θ of the clearance 30 is 20 ° or less, specifically, 14 ° to 16 °, and since a predetermined step remains between the rear end of the margin 20 and the second cutting surface 28, the margin The friction reducing effect of the escape 30 can be sufficiently enjoyed while sufficiently securing the strength of 20.

FIG. 3 shows test pieces A and B of the present embodiment in which the relief 30 is provided so that the drill diameter D = 6 mm and the remaining dimension t ₂ ≒ 0.2 mm, and the remaining dimension t in the above embodiment. ₂ Test sample C for comparison with ≒ 0.6 mm,
Using D and drilling under the following cutting conditions, the result of examining the number of machined holes until reaching the predetermined tool life specified by the wear width of chipping and outer peripheral wear, etc. The tool life of the products A and B is about twice as long as the test products C and D for comparison. FIG. 4 shows the results of examining the enlargement allowance of the machined hole during the above test, that is, the machining dimensional error.
“□” and “■” are test samples C and D,
In the case of D, the enlargement allowance is about 0.02 to 0.04 mm, whereas in the test products A and B of the present embodiment, it is 0.02 mm or less, so that the sharpness is improved and the processing accuracy is improved. In addition,
Leaving dimension t ₂ is greater specimen C, the life cause of D is an increase in the wear width of the outer wear. (Cutting conditions) Work material: S50C (Carbon steel for machine structure) Cutting speed: 120 m / min Feed: 0.18 mm / rev Hole depth: 25 mm through hole Cutting oil: Water soluble

The embodiments of the present invention have been described in detail with reference to the drawings. However, these embodiments are merely examples, and the present invention is based on the knowledge and knowledge of those skilled in the art. Can be implemented.

[Brief description of the drawings]

FIG. 1 is a view showing a drill according to an embodiment of the present invention;
(a) is a front view, (b) is an enlarged front view of a tip portion, and (c) is an enlarged bottom view as viewed from the tip side.

FIG. 2 is a sectional view showing the vicinity of a margin in the II-II section of FIG. 1 (a), wherein (a) is a state after a relief is provided,
(b) is a state before the escape is provided.

FIG. 3 is a diagram showing the results of a durability test performed using the test articles A and B of the embodiment of FIG. 1 and test articles C and D for comparison with a residual dimension t ₂ ≒ 0.6 mm. is there.

4 is a result of examining an enlargement allowance of a machined hole obtained in the test of FIG. 3; “、” and “●” indicate test pieces A and B; “□” and “■” indicate test pieces C and D; It is.

FIG. 5 is a diagram showing another example of a relief shape provided in a margin, and is a diagram corresponding to FIG. 2 (a).

FIG. 6 is a view showing still another example of a relief shape provided in a margin, and is a view corresponding to FIG. 2 (a).

[Explanation of symbols]

 10: drill 18: groove 20: margin 2
6: Leading edge 28: Second cut surface 30: Escape O: Shaft center
t₁: Margin width t _Two: Remaining dimensions θ: Escape escape
Angle

Claims (3)

[Claims] 1. A drill provided with a margin along a groove, wherein the margin has a predetermined residual area in a range of 0.1 mm to 0.5 mm on a leading edge side in a cross section perpendicular to an axis. leaving only the dimension t _2, the drill, characterized in that relief is provided to smoothly inclined toward the opposite side of the rear end and the leading edge. 2. The drill according to claim 1, wherein the remaining dimension t ₂ is not more than ／ of a margin width t ₁ of the margin. 3. The clearance angle θ of the clearance in the cross section.
3. The drill according to claim 1, wherein the angle is 20 ° or less, and a predetermined step remains between a rear end of the margin and the second cutting surface. 4.