JPH11188519A - Minor diameter throw-away drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To surely set and precisely position an insert in a prescribed position of a slit by rotatably installing a positioning ball energized to the opposed surface of a drill insert by an elastic body into a holder, and providing a dimple in the part corresponding to the ball. SOLUTION: A minor diameter throw-away drill 10 has a drill insert 1 installed into a slit formed on the front end part of a holder 11 by a fixing bolt. An elastic body 41 is interposed to a through-hole formed on the holder 11, and a positioning ball 42 is rotatably installed thereto. The positioning ball 42 energized in the direction for pressing the tapered surface of the conical dimple 9b of the insert 1 by the elastic body 41 is held by overhangs. According to this, the insert can be surely set in a prescribed position and precisely positioned.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a small-diameter indexable drill for drilling holes.

[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.

[0006] However, the problem with the indexable drill S for small diameter machining is that the rear end of the insert 30 is hidden in the holder and is difficult to see, so that the rear end face of the insert is in contact with the opposing surface of the holder. In order to control the diameter of the hole of the bolt of the insert with very high accuracy,
There is a problem that a process such as polishing is required, and the production cost is increased.

[0007]

SUMMARY OF THE INVENTION In view of the problems of the prior art, according to the present invention, a plate-shaped drill insert is mounted with a fixing bolt in a slit provided at a front end of a holder. It is an object of the present invention to provide a small-diameter throw-away drill in which an insert is securely installed at a predetermined position of a slit so that accurate positioning can be performed even if a bolt hole wall of the insert is not precisely machined by polishing. .

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, the present invention provides a small diameter throw insert in which a plate-shaped drill insert is mounted with fixing bolts in a slit provided at a front end of a holder. In an away drill, an engagement sliding contact between a positioning ball urged by an elastic body such as a spring and a corresponding conical dimple is used.

Specifically, a positioning ball urged by an elastic body such as a spring on a surface facing the drill insert is rotatably mounted inside the holder. And, the opposing surface of the drill insert is provided with a conical dimple at a portion corresponding to the ball.

[0010] When the fixing ball is fastened, the positioning ball and the conical dimple come into sliding engagement with each other, whereby the drill insert is drawn inward.

The drill insert can be set at a predetermined position by arranging the conical dimple so that the conical vertex (bottom point) is behind the vertex of the positioning ball.

[0012]

In the small diameter throw-away drill of the present invention, a plate-shaped drill insert is mounted with a fixing bolt in a slit provided at the front end of the holder.

When the fixing bolt is tightened, it is urged by an elastic body such as a spring provided inside the holder, and is positioned on the surface of the drill insert facing the positioning ball with its head exposed. The tapered surface of the conical dimple provided abuts, and the tapered surface attempts to push down the ball. At this time, the engagement between the tapered surface and the ball causes the ball to rotate, and The drill insert is also urged in the direction in which the ball rotates by frictional force with the ball.

By utilizing such movement, the drill insert is set at a predetermined position.

[0015]

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

FIG. 1 shows 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 and an outer cutting edge 3 for cutting an outer peripheral side at a front end of a polygonal plate-like body.
In order to form the inner cutting edge 2 and the outer cutting edge 3 at substantially the same height at an intermediate position corresponding to the total thickness L of the plate-like body, the rake faces of the inner cutting edge 2 and the outer cutting edge 3 are respectively provided. Reference numerals 4 and 5 are provided below the step. 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. .

Here, the corners formed by straight lines continuing to the curved portions with the corner R portions 6 and 7 are close to a right angle, and
It refers to those in the range of ° to 105 °.

A bolt fixing hole 9a and a conical dimple 9b are formed on a flat surface 9 which is further raised from the rake face 5 connected to the outer cutting edge 3 of the drill insert 1.

FIGS. 2 and 3 show the drill insert 1 described above.
1 shows a small-diameter throw-away drill 10 equipped with a small-diameter throw-away drill (hereinafter, abbreviated as a drill).
A drill insert (hereinafter abbreviated as “insert”) 1 is mounted with a single fixing bolt 13 in a slit 15 formed in a front end portion 12 of a holder 11. 3, the center 13a of the fixing bolt 13 is displaced from the center axis 11a of the holder 11 in the direction of the outer cutting edge 3, as shown in FIG.

In the drill 10, since the fixing bolt 13 is displaced in the direction of the outer cutting edge 3 in this manner, 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 largely different, the thickness of the insert 1 is increased, and the mechanical strength of the holder 11 may be reduced.

FIG. 4 is a sectional view taken along line AA of FIG. 3. As shown in FIG. 4, a positioning ball is formed by interposing an elastic body 41 such as a spring in a through hole 40 formed in the holder 11. 42 is rotatably mounted. The elastic body 4
The positioning ball 41 urged in the direction of pressing the tapered surface 9c of the conical dimple 9b of the insert 1 by the insert 1 is held by overhang so that only its head 42 is exposed.

The conical dimple 9b of the conical dimple 9b is arranged such that the conical vertex (bottom point) 9d is located rearward of the vertex 44 of the positioning ball 42.

In order to explain the operation of the positioning ball 42 and the conical dimple 9b, when the fixing bolt 13 is tightened, it is urged by an elastic body 41 such as a spring provided in the through hole 40. Is inserted into the positioning ball with the head 43 exposed.
The tapered surface 9c of the conical dimple 9b provided on the opposing surface of the ball 42 contacts the ball 42.
At this time, the taper surface 9c
And the ball 42, the ball 42 rotates, and at the same time, the insert 1 is urged in the direction in which the ball rotates, that is, backward by the frictional force with the ball 42, and the insert 1 Can be drawn into.

The tapered angle β of the conical dimple 9b is preferably in the range of 5 ° to 20 °. If the taper angle β is less than 5 °, the force for pulling the insert 1 backward is weak, while if it exceeds 20 °, even if the ball 42 rotates, the frictional force for pulling the insert 1 backward may be less likely to act. Because there is.
Further, the diameter of the ball 42 is preferably in the range of about 1 to 2 mm.

As shown in FIG. 5, another embodiment of a drill 10 is provided with a positioning ball 42 urged by an elastic body 41 such as a spring at two places of a holder 11 so as to be rotatable. On the other hand, a configuration in which conical dimples 9b are provided on both the upper side and the lower side of the insert 1 at corresponding positions on the upper side and the lower side of the insert may be adopted. By utilizing the sliding contact between the ball 42 and the dimple 9b at a plurality of locations in this manner, the installation of the insert 1 at a desired position can be made more reliable.

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.

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. .

[0032]

As described above, according to the present invention, there is provided a small-diameter throw-away drill in which a plate-shaped drill insert is mounted with a fixing bolt in a slit provided at a front end of a holder. By using the engaging sliding contact between the positioning ball urged by the elastic body and the corresponding conical dimple, the bolt hole wall of the insert is not machined with high precision by polishing. Even so, there is an excellent effect that the insert can be securely installed at a predetermined position and accurate positioning can be performed.

[Brief description of the drawings]

FIG. 1 is a perspective view of a drill insert constituting a small-diameter throw-away drill of the present invention.

FIG. 2 is a perspective view of a small-diameter throw-away drill according to the present invention.

FIG. 3 is a plan view of the small-diameter indexable drill shown in FIG. 2;

FIG. 4 is a sectional view taken along line AA of FIG. 3;

FIG. 5 is a cross-sectional view of the small-diameter throw-away drill of FIG. 2;

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 blade 4,5 Rake surface 6,7 Corner R part 8 Projection 9a Bolt fixing hole 9b Dimple 9c Tapered surface 9d Conical apex (bottom point) 10 Indexable drill 11 Holder 11a Center axis 12 front end 13 fixing bolt 13a fixing center 14 pocket 15 slit 40 through hole 41 elastic body 42 ball 43 head 44 vertex L total thickness γ bending angle β taper angle

Claims (3)

[Claims] 1. A slit provided at a front end of a holder,
A throw-away drill in which a plate-shaped drill insert is mounted with fixing bolts, and a positioning member which is biased by an elastic body such as a spring against an opposing surface of the drill insert inside a holder. The ball is rotatably provided, and the opposing surface of the drill insert is provided with a conical dimple at a portion corresponding to the ball, and the positioning ball and the conical dimple are provided when the fixing bolt is fastened. A small-diameter indexable drill configured to install a drill insert at a predetermined position by engaging and sliding engagement. 2. The taper angle of said conical dimple is 5
The small-diameter indexable drill according to claim 1, wherein the angle is in the range of 20 to 20 °. 3. The small diameter throw-away drill according to claim 1, wherein a conical vertex of the conical dimple is arranged at a predetermined position side from a vertex of the positioning ball.