JPH11188518A - Drill insert and indexable drill using the same - Google Patents

Abstract

[PROBLEMS] To improve chip dischargeability without sacrificing cutting performance, particularly in a throw-away drill used for drilling small-diameter holes. SOLUTION: In a throw-away drill 10 in which a drill insert 1 having both an inner cutting edge 2 and an outer cutting edge 3 is mounted with one fixing bolt 13, a center shaft 13a of the fixing bolt 13 is held by a holder. By displacing the central cutting edge 11 from the center axis 11a in the direction of the outer cutting edge 3, a large chip discharging pocket 14 is secured above the rake face 4 of the inner cutting edge 2 (on the rotational direction side).

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill insert for drilling a hole and a throw-away drill using the same.

[0002]

2. Description of the Related Art As a drill tool for drilling, an outer cutter insert on an outer peripheral side and an inner cutter insert on an inner peripheral side are detachably mounted so that mutual rotation trajectories intersect at the tip of a tool body. Has been commonly used.

FIG. 6 shows such a throw-away drill T.

[0004] The drill insert 20 to be mounted on the throw-away drill T has a cutting edge formed on the ridge of the upper surface 21. As shown in FIG. , Each outer blade insert 22,
The inner blade insert 23 is mounted with the upper surface 21 facing in the same rotation direction. In addition, the rotation trajectories of the cutting edge serving as the bottom cutting edge 25 among the cutting edges formed on the outer cutter insert 22 and the inner cutter insert 23 intersect and cover from the central axis T1 of the throw-away drill T to the side surface T2. .

On the other hand, in the case of drilling a small-diameter hole of φ10 or less, the screw must be made very small, and a screw having such a shape cannot be used because of its strength. A single insert having a shape like a letter has been used at the front end. FIG. 7 shows such a throw-away drill S for small-diameter machining. As shown in FIG. 7, the thin plate-shaped insert 30 has a width larger than the holder diameter.
The cutting edge 31 in which the inner cutting edge and the outer cutting edge were integrated was formed on the upper and lower ridge sides of the front end.

The above-mentioned indexable drill S for small diameter machining
Some of them are fixed with two fixing bolts, but there is a problem that the mechanical strength is small and the processing area is very narrow. On the other hand, the one using one fixing bolt has been improved in terms of mechanical strength, but since the fixing bolt acts on the center axis of the holder,
In particular, there is little space for discharging chips from the inner peripheral side, and there has been a large problem in chip dischargeability.

[0007]

SUMMARY OF THE INVENTION In view of the above-mentioned problems in the prior art, the present invention improves the chip dischargeability without sacrificing the cutting performance, particularly in a throw-away drill used for drilling small-diameter holes. That is the task.

[0008]

In order to solve the above problems, the present invention provides a drill insert having a polygonal plate-shaped body having both an inner cutting edge and an outer cutting edge at the front end of a holder.
In the throw-away drill mounted with the fixing bolts, the center axis of the fixing bolt is displaced from the center axis of the holder in the direction of the outer cutting edge, so that the rake face of the inner cutting edge ( It is possible to secure a large pocket for chip discharge on the rotation direction side).

As one means for making a throw away drill having such a structure, an inner cutting edge and an outer cutting edge are formed at substantially the same height at an intermediate position corresponding to the entire thickness of the plate-like body. A drill insert having a cutting blade bent in the radial direction and having a width smaller than the diameter of the holder can be used.

For example, when the above-mentioned drill insert is used, the insert is mounted on the front end of the holder. At this time, when the drill insert is mounted so as to be biased so that the corner of the outer cutting edge is located at the outermost peripheral position, the drill is inserted. The center axis of the insert is shifted from the center axis of the holder toward the outer cutting edge. By bringing the bolt center axis of the drill insert on this center axis, it is possible to secure a large pocket for chip discharge on the inner cutting edge side.

In addition, since the inner cutting edge is bent in the lyal direction, the pocket can be made larger, and the bent shape as described above improves the machinability.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, embodiments of the present invention will be described with reference to the drawings.

FIGS. 1 and 2 show a drill insert 1 according to this embodiment. The drill insert 1 has an inner cutting edge 2 for cutting an inner peripheral side of a processing hole at a front end of a polygonal plate-like body.
And the outer cutting edge 3 for cutting the outer peripheral side, wherein the inner cutting edge 2 and the outer cutting edge 3 have substantially the same height at an intermediate position for the entire thickness L of the plate-like body. , The rake faces 4 and 5 of the inner cutting edge 2 and the outer cutting edge 3 are provided in a stepwise manner. Further, the inner cutting blade 2 is formed so as to bend in the radial direction at an intermediate position.

In addition, the outer cutting edge 3 of the drill insert 1 is provided with a pair of corner R portions 6 and 7 at the corners thereof, thereby forming a projecting portion 8 slightly projecting forward. .

In the present invention, the corner R portions 6, 7
Means that the angle formed by the straight line continuing to the curved portion is close to a right angle, and 6
It refers to one in the range of 0 ° to 105 °. FIG. 3 to FIG.
1 shows a throw-away drill 10 to which the above-mentioned drill insert 1 is attached. The throw-away drill (hereinafter, abbreviated as a drill) 10 is provided at a front end portion 12 of a holder 11 with the drill insert (hereinafter, abbreviated as an insert) 1.
Is attached with a single fixing bolt 13, the width of the insert 1 is made smaller than the diameter of the holder 11, and the center axis 13 a of the fixing bolt 13 is set at the center of the holder 11 as shown in FIG. It is displaced from the shaft 11a in the direction of the outer cutting edge 3.

In the drill 10, since the fixing bolt 13 is displaced in the direction of the outer cutting edge 3, a very large chip discharging pocket 14 is provided on the side of the rake face 4 of the inner cutting edge 2 in the rotation direction. Can be secured. Moreover,
Since the inner cutting edge 2 is bent at a bending angle γ = 10 ° to 20 ° in the radial direction, the pocket 14 can be made larger.

When the bending angle γ is less than 10 °,
In addition to the possibility that the chip discharge performance may be deteriorated, there is a possibility that the effect of bending the holder 3 toward the outer cutting blade 3 by weakening the combined force of the radial load described below toward the outer cutting blade 3 may be weakened. is there.

On the other hand, if the bending angle γ exceeds 20 °, the lower thickness of the inner cutting edge 2 decreases, and as a result, the mechanical strength may decrease.

If the height of the outer cutting edge 3 and the height of the inner cutting edge 2 are greatly different from each other, the thickness of the insert 1 increases, and the mechanical strength of the holder 11 may be reduced.

Incidentally, the drill 10 has the protruding portion 8 of the outer cutting edge 3 on the outermost peripheral side. The protruding portion 8 includes a pair of the corner R portions 6 and 7.
There is an effect of changing the direction of the radial load of the outer cutting edge 3 to the rotation direction side. As a result, the direction of the combined force of the radial load of the inner cutting edge 2 and the radial load of the outer cutting edge 3 is adjusted to the center axis 11 of the holder.
a to the outer cutting edge 3 and the holder 11
Is bent toward the outer cutting blade 3. Therefore, the processing diameter becomes large, and when the drill 10 is pulled out from the processing hole, the outer cutting blade 3 can be pulled out without contact with the hole wall.
The processed surface can be made good. Although the inner cutting edge 2 is bent in the radial direction at the intermediate portion, the radial load of the inner cutting edge 2 is somewhat increased by this bending.
, Which reinforces the operation of the protrusion 8.

The protruding portion 8 has the function of dividing chips into small pieces. At the time of cutting, chips from the hole bottom surface on the outer peripheral side have the property that the cutting speed is high, and difficult-to-cut materials such as stainless steel are stretched and easily entangled with the holder 11, but the chips are finely divided so that they are satisfactorily discharged without entanglement Is done. On the other hand, according to the inner cutting blade 2, the chip discharge speed is low, but the chip 14 can be discharged without stagnation because the pocket 14 is large.

As described above, the embodiment of the present invention has been illustrated with reference to the drawings. However, it is needless to say that the present invention is not limited to the above-described embodiment, and can be in any form without departing from the object of the invention. .

[0023]

As described above, according to the present invention, a drill insert having both an inner cutting edge and an outer cutting edge on a polygonal plate-like body is provided at the front end of the holder with one fixing bolt. In the throw-away drill mounted in advance, the center axis of the fixing bolt is displaced from the center axis of the holder in the direction of the outer cutting edge, so that the center axis is larger above the rake face of the inner cutting edge (rotation direction side). It is possible to secure a pocket for chip discharge.

An inner cutting edge and an outer cutting edge are provided at substantially the same height at an intermediate position corresponding to the entire thickness of the plate-like body, and a drill insert formed by bending the inner cutting edge in the radial direction is provided. When used in a throw-away drill, the following extremely excellent effects can be obtained.

That is, when the width of the drill insert is made smaller than the diameter of the holder and the drill insert is biased so that the corner of the outer cutting edge is located at the outermost peripheral position, the center axis of the drill insert becomes the center axis of the holder. From the outer cutting edge. By bringing the bolt center axis of the drill insert on this center axis, it is possible to secure a large pocket for chip discharge on the inner cutting edge side. Moreover,
Since the inner cutting edge is bent in the lyal direction, the pocket can be made larger, and the bent shape as described above improves the machinability.

[Brief description of the drawings]

FIG. 1 is a perspective view of a drill insert according to the present invention.

FIG. 2 is a perspective view of a drill insert according to the present invention.

FIG. 3 is a perspective view of the throw-away drill of the present invention.

FIG. 4 is a perspective view of the throw away drill of the present invention.

5 is a plan view of the throw-away drill of FIGS. 3 and 4. FIG.

FIG. 6 is a plan view of a conventional indexable drill equipped with two inserts.

FIG. 7 is a plan view of a conventional indexable drill for small-diameter machining to which one insert is mounted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Drill insert 2 Inner cutting edge 3 Outer cutting edge 4,5 Rake face 6,7 Corner R part 8 Projection 10 Throw-away drill 11 Holder 11a Center axis 12 Front end 13 Fixing bolt 13a Center axis 14 Pocket L Total thickness γ Bending angle

Claims (4)

[Claims] 1. A drill insert having, at a front end of a plate-shaped body having a polygonal shape, an inner cutting edge for cutting an inner peripheral side of a processing hole and an outer cutting edge for cutting an outer peripheral side thereof. A drill insert wherein the inner cutting edge and the outer cutting edge are formed at substantially the same height at an intermediate position corresponding to the entire thickness of the body, and the inner cutting edge is bent in the radial direction. 2. The radial bending angle of the inner cutting edge is 10 °.
The drill insert according to claim 1, wherein the angle is set to 20 °. 3. The drill insert according to claim 1, wherein a pair of corners R are formed at the corners of the outer cutting edge. 4. A throw-away drill in which a polygonal plate-shaped drill insert having both an inner cutting edge and an outer cutting edge is attached to a front end portion of a holder with one fixing bolt. A throw-away drill, wherein the width of the drill insert is smaller than the diameter of the holder, and the center axis of the fixing bolt is displaced from the center axis of the holder toward the outer cutting edge.