JP2579452Y2 - Drill - Google Patents

Description

[Detailed description of the invention]

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a drill,
The present invention relates to a drill that can reliably prevent run-out.

[0002]

2. Description of the Related Art Generally, in a lathe or a cylindrical grinder, a relatively shallow conical center hole is formed at an end of a workpiece in order to support the workpiece at the center of rotation of the workpiece. The tool is fixed to the spindle or tailstock by a tool called a center having a shape that fits into the center hole. A so-called center drill is used as a tool for forming the center hole when performing such center work or centering work. The drill is angled from the drill end 2 to the shank 4 as shown in FIG. 5 to taper the opening to form a shallow conical center hole in the workpiece as described above. And a spiral groove 8 is formed in this portion to form a cutting groove 10 for cutting. And such a blade groove part 10 is formed in the both ends of the shank part 4 on both sides, and is comprised as what is called a double-edge drill.

Since the purpose of this drill is to form a shallow center hole as described above, the blade groove 8 is formed by a conventional electric drill intended to machine a through hole or a deep hole. Instead of a relatively long continuous complete spiral like other drills, such as drills and carbide drills, they are slightly wound circumferentially around the drill body and are largely carved. As shown in FIG. 6, for example, the shank portion 4 of the chuck 12 is gripped and attached to a rotating shaft of a center drill blade, a center hole device, a lathe or the like formed as described above. .

[0004]

However, as described above, the center hole formed by the center drill must be formed with extremely high precision because it is used for positioning the workpiece. However,
In the above-described drill, the end of the blade groove 8 is carved to the shank portion 4 beyond the tapered portion 6, and the boundary between the blade groove portion 10 and the shank portion 4 is unclear. Therefore, when the drill is clamped by the chuck 12, for example, two claw portions 14a,
14b respectively correspond to the blade portions 16 and come into contact therewith, but the remaining one claw portion 14c has a portion corresponding to the groove portion 18 that does not contact the drill, and a gap is formed between the blade groove and the claw portion 14. S may occur.

[0005] In such a gap S, the clamping pressure does not act, so that a relief F of the force is generated, and the pressing force of the claw portion 14 of the chuck 12 against the drill is slightly biased. When the drill is rotated in such a state, the drill rotates while slightly swinging in a direction perpendicular to the axis, and as a result, the accuracy of drilling the center hole is deteriorated. was there.
In addition, there is also a problem that stress is applied to the drill due to runout of the drill itself, thereby shortening its life. The present invention
Focusing on the above problems, it was created to effectively solve them. An object of the present invention is to provide a drill capable of making the pressing force of the chuck uniform.

[0006]

SUMMARY OF THE INVENTION In order to solve the above problems, the present invention provides a center drill having a blade groove at both ends of a shank for forming a center hole of a workpiece . the amount relief than the diameter of the blade groove the diameter of the shank portion with completely partitions the said blade groove and the shank portion
It is configured to be set slightly larger by a corresponding amount .

[0007]

The present invention is constructed as described above, so that the claw portion of the chuck 12 is separated from the blade groove portion and comes into contact only with the shank portion whose diameter is slightly increased to grip it. Therefore, the pressing force of the claw portion acts uniformly on the drill, and the drill is reliably positioned on the axis, and does not run out during rotation.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the center drill according to the present invention will be described below in detail with reference to the accompanying drawings. FIG. 1 shows the present invention.
FIG. 2 is a plan view showing an embodiment of a center drill, and FIG. 2 is a view showing a state where the drill is attached to a chuck. As shown in the figure, the center drill 20 is, for example, a center drill for forming a center hole of a work, and
It is mainly constituted by a shank portion 22 formed in a straight line shape gripped by the second claw portion 14, and blade grooves 24, 24 formed at both ends of the shank portion 22 so as to sandwich the shank portion 22. Each of the blade grooves 24 is mainly composed of a tapered portion 28 continuing to the cutting edge 26 and a cylindrical portion 30 having a uniform radius continuing to the tapered portion 28. The tapered portion 28 and the cylindrical portion 30 extend from the cutting edge 26. As in the conventional drill, a relatively large blade groove 32 slightly spirally formed is formed. Since the drill in this embodiment is used, for example, as a center drill for forming a center hole at the time of centering, the lengths L1 and L2 of the blade groove portions 26 depend on the drill diameter, but when the drill diameter is 6 mm, For example, L1 =
When the drill diameter is set to about 7.5 mm and L2 = 2 mm and the drill diameter is 7.8 mm, for example, L1 = 11.0 mm and L2 =
Set to about 3 mm. Also, the angle α of the tapered portion 28
Is set to an appropriate value such as, for example, 60 °, 75 °, or 90 ° depending on the application.

On the other hand, the shank portion 22 is set slightly larger than the blade groove 24, that is, the diameter of the cylindrical portion 30 of the blade groove 24, is slightly thicker than the diameter, and is completely formed with the blade groove 24. It is compartmentalized. The shank portion 22 has a uniform diameter because this portion is gripped by the chuck, and is preferably formed to be relatively long in the axial direction in order to perform reliable clamping. If the length of the shank portion 22 is too short, the drill will be clamped in a point contact state, and the clamping force will be weak, and the drill will resonate due to rotational motion and vibrations generated during grinding. Would be. Accordingly, as described above, the length of the shank portion 22 is set to a sufficient length and fixed in a planar contact state, thereby increasing the reliability of the holding state.

The effect of the difference between the radius of the cylindrical portion 30 and the radius of the shank portion 22, that is, the amount of relief M, does not change even if it is too large.
Set to about m. Next, the operation of the present embodiment configured as described above will be described. As shown in FIG. 2, one end of a drill 20 is inserted into a chuck 12 such as a lathe or a cylindrical grinder, and this is pressed and gripped by three or four claws 14. In this case, the shank part 22 is
Since the diameter of the cylindrical portion 30 is slightly larger than that of the cylindrical portion 4, the claw portion 14 contacts and presses and grips only the shank portion 22, and the claw portion 14 and the blade groove 32 are formed. There is no contact with not only the blade groove 24, that is, the tapered portion 28 but also the columnar portion 30.

Therefore, as shown in FIG. 3, in the longitudinal direction of the shank portion 22 of the drill 20, the upper end portion of the shank portion 22 is evenly in contact with the claw portion 14, and in this portion, the drill center direction is uniform. A pressing force is applied toward. Therefore, in the conventional drill, the claw portion of the chuck and the drill were unevenly contacted due to the influence of the blade groove.
In this embodiment, the clamp pressure of the claw portion 14, that is, the pressing force uniformly acts on the drill, so that the drill is securely positioned and does not shake during this rotation.

In the above embodiment, the tapered portion 28
Has been described as a single-stage case, but is not limited thereto.
For example, as shown in FIG. 4, the tapered portion 28 is formed by a first tapered portion 28a having an angle α = 60 ° and a subsequent second tapered portion 28b having an angle β = 120 °.
It is needless to say that the present invention can be applied to a stepped structure.

[0013]

As described above, according to the present invention, the following excellent functions and effects can be exhibited. Since the clamp pressure can be uniformly applied to the drill without being affected by the blade groove, the positioning of the drill can be reliably performed, and therefore, the drill itself can be prevented from swinging during rotation. Therefore, the accuracy of the center hole can be greatly improved, and the life of the drill can be extended since there is no undesired deflection.

[Brief description of the drawings]

FIG. 1 is a plan view showing a center drill according to the present invention.

FIG. 2 is a diagram showing a state in which the center drill according to the present invention is fixed to a chuck.

FIG. 3 is a bottom view showing a state in which the drill in FIG. 2 is viewed from below.

FIG. 4 is a plan view showing a drill according to another embodiment of the present invention.

FIG. 5 is a diagram showing a state in which a conventional drill is fixed to a chuck.

FIG. 6 is an explanatory diagram illustrating a state in which the clamping pressure of a conventional drill becomes non-uniform.

[Explanation of symbols]

 Reference Signs List 12 chuck 14 claw 20 drill 22 shank 24 blade groove 28 taper 30 cylindrical part 32 blade groove M relief amount

Claims (2)

(57) [Scope of request for utility model registration] A center drill having blade grooves at both ends of a shank portion for forming a center hole of a workpiece .
The blade groove portion and the shank portion are completely partitioned, and the diameter of the shank portion is equivalent to the relief amount than the diameter of the blade groove portion.
A center drill characterized in that it is configured to be set slightly larger as much as possible. 2. The relief amount is 0.5 m in radius.
2. The center drill according to claim 1, wherein the center drill is in a range of m to 1.0 mm .