JPH0520812U - Drill - Google Patents

Abstract

(57) [Summary] [Purpose] The clamping pressure from the chuck is applied uniformly to the drill. In a drill having blade groove portions 24, 24 at both ends of a shank portion 22, the blade groove portion 24 and the shank portion 2 are provided.
2 is completely partitioned so that a blade groove is not formed in the shank portion 22, and the diameter of the shank portion 22 is set to be slightly larger than the diameter of the blade groove portion 24 so that the chuck claw portion 14 is shank-shaped. Only the part 22 is contacted.

Description

[Detailed description of the device]

[0001]

[Industrial applications]

 The present invention relates to a drill, and more particularly to a drill that can reliably prevent runout.

[0002]

[Prior Art]

 Generally, in a lathe or a cylindrical grinder, a relatively shallow conical center hole is formed at the end of the work to support the work at the center of rotation of the work, and the center hole is fitted into the center hole. It is fixed to the spindle or tailstock by a tool called a center having a shape. A so-called center drill is used as a tool for forming the center hole when performing such center work or centering work. As shown in FIG. 5, this drill has a predetermined angle from the drill end 2 to the shank 4 in order to taper the opening to form a shallow conical center hole in the workpiece as described above. It has a tapered portion 6 formed therein, and a spiral blade groove 8 is formed in this portion to form a blade groove portion 10 for cutting. The blade groove portion 10 is formed at both ends of the shank portion 4 so as to sandwich the shank portion 4, and is configured as a so-called double-edged drill.

Since the purpose of this drill is to form a shallow center hole as described above, the blade groove 8 of the drill is a normal electric tool for processing through holes and deep holes. Unlike other drills such as air drills and carbide drills, it is not a relatively long continuous perfect spiral shape, but is slightly wound in the circumferential direction with respect to the drill body and engraved largely. As shown in FIG. 6, for example, the shank portion 4 is attached to the rotary shaft of the center drill blade, the center hole device, or the lathe thus formed, which is gripped by the three claw portions 14 of the chuck 12. It

[0004]

By the way, the center hole formed by the center drill as described above is for positioning the workpiece, and therefore must be formed with extremely high accuracy. However, in the above-described drill, the edge of the groove 8 is carved up to the shank portion 4 beyond the tapered portion 6, and the boundary between the groove portion 10 and the shank portion 4 is unclear. Therefore, when the drill is clamped by the chuck 12, for example, two claws 14a and 14b are respectively in contact with the upper part of the claw 14 as shown in FIG. However, the remaining one claw portion 14c may have a portion that does not come into contact with the drill in correspondence with the groove portion 18, and thus a gap S 2 may occur between the blade groove and the claw portion 14.

In such a gap S, since the clamp pressure does not work, a force relief F is generated, and the pressing force of the claw portion 14 of the chuck 12 against the drill is slightly biased. If the drill is rotated in such a state, the drill will rotate while swinging slightly in a direction orthogonal to this axis, resulting in deterioration of the accuracy of drilling the center hole. There was a point. There is also a problem that stress is applied to the drill itself due to the runout of the drill itself and the life of the drill is shortened. The present invention has been devised in order to effectively solve the above problems. An object of the present invention is to provide a drill capable of making the pressing force of the chuck uniform.

[0006]

[Means for Solving the Problems]

 In order to solve the above problems, the present invention provides a drill having blade grooves at both ends of a shank portion, in which the blade groove portion and the shank portion are completely partitioned and the diameter of the shank portion is set to the diameter of the blade groove portion. It is configured to be set slightly larger than.

[0007]

[Action]

 Since the present invention is configured as described above, the claw portion of the chuck 12 comes into contact with and grips only the shank portion that is separated from the blade groove portion and has a slightly larger diameter. The pressing force of the part acts evenly on the drill, the drill is accurately positioned on the axis, and there is no runout during rotation.

[0008]

【Example】

 Hereinafter, an embodiment of a drill according to the present invention will be described in detail with reference to the accompanying drawings. 1 is a plan view showing an embodiment of a drill according to the present invention, and FIG. 2 is a view showing a state in which the drill is attached to a chuck. As shown in the figure, the drill 20 is a center drill for forming a center hole of a workpiece, for example, and has a linear shank portion 22 to be gripped by the claw portions 14 of the chuck 12 and shank portions at both ends thereof. It is mainly configured by blade groove portions 24, 24 formed so as to sandwich the portion 22. Each of the blade groove portions 24 is mainly configured by a tapered portion 28 that is continuous with the blade edge 26 and a columnar portion 30 that is continuous with the tapered portion 28 and has a uniform radius. A relatively large blade groove 32, which is slightly spiral-shaped like the conventional drill, is formed over the portion 30. Since the drill in this embodiment is used 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 = 7.5 mm and L2 = 2 mm are set, and when the drill diameter is 7.8 mm, for example, L1 = 11.0 mm and L2 = 3 mm are set. The angle α of the taper portion 28 is set to an appropriate value such as 60 °, 75 ° or 90 ° according to the application.

On the other hand, the shank portion 22 is set to have a diameter slightly larger than the diameter of the blade groove portion 24, that is, the cylindrical portion 30 of the blade groove portion 24, and is made slightly thicker than this, so that the shank portion 24 is completely It is divided into compartments. 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 for reliable clamping. If the length of the shank portion 22 is too short, the drill will be clamped in a point contact state, so the clamping force will be weak and the drill will resonate due to rotational movement or vibration generated during grinding. It will be lost. Therefore, by setting the length of the shank portion 22 to a sufficient length and fixing the shank portion 22 in a surface contact state as described above, the certainty of the holding state is increased.

Further, the difference in radius between the columnar portion 30 and the shank portion 22, that is, the relief amount M does not change even if the amount is too large, and is preferably set to about 0.5 to 1.0 mm, for example. .. Next, the operation of this embodiment configured as described above will be described. As shown in FIG. 2, one end of the drill 20 is inserted into a chuck 12 such as a lathe or a cylindrical grinder, and the drill 20 is pressed and held by three or four claws 14. In this case, since the shank portion 22 is set to have a diameter slightly larger than the diameter of the cylindrical portion 30 of the blade groove portion 24, the claw portion 14 comes into contact with only the shank portion 22 and presses and grips it, and the claw portion 14 The blade groove portion 24 in which the blade groove portion 32 is formed, that is, the taper portion 28, and the columnar portion 30 are not in contact with each other.

Therefore, as shown in FIG. 3, in the length direction of the shank portion 22 of the drill 20, the claw portion 14 is evenly contacted to the upper end portion of the shank portion 22, and in this portion, the direction of the drill center is even. A pressing force is applied toward. Therefore, in the conventional drill, the claw portion of the chuck and the drill were unevenly contacted by the influence of the blade groove, but in the present embodiment, the clamping pressure of the claw portion 14, that is, The pressing force acts evenly on the drill, ensuring that the drill is properly positioned and does not run out during this rotation.

In the above embodiment, the case where the taper portion 28 has a single step has been described, but the present invention is not limited to this. For example, as shown in FIG. 4, the taper portion 28 may have an angle α = 60 °. It is needless to say that the first taper portion 28a and the second taper portion 28b subsequent to the first taper portion 28a and having the angle β = 120 °, for example, can be applied to the two-stage structure.

[0013]

[Effect of the device]

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

[Brief description of drawings]

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

FIG. 2 is a view showing a state in which a 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 view 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 clamp pressure of a conventional drill becomes uneven.

[Explanation of symbols]

 12 chuck 14 claw portion 20 drill 22 shank portion 24 blade groove portion 28 taper portion 30 columnar portion 32 blade groove M escape amount

Claims (2)

[Scope of utility model registration request] 1. A drill having blade groove portions at both ends of a shank portion, wherein the blade groove portion and the shank portion are completely divided, and the diameter of the shank portion is set to be slightly larger than the diameter of the blade groove portion. A drill characterized by being configured. 2. The drill according to claim 1, wherein the drill is a center drill for forming a center hole of a workpiece.