JPH08338B2 - Tool holder - Google Patents

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a tool holder for mounting various cutting tools on a spindle of a machine tool.

[0002]

2. Description of the Related Art In a tool holder of this type, a tapered shank portion is fitted in a tapered shaft hole of a main shaft on a machine tool side, and a pull bolt screwed and fixed to a tip end of the tapered shank portion is installed inside the main shaft. By being pulled in by a holder pull-in means called a draw bolt, the tapered surface of the tapered shank portion and the inner peripheral surface of the tapered shaft hole on the spindle side are brought into close contact with each other and attached to the spindle.

Conventionally, triangular screws have been conventionally used as screws for the taper shank portion and the threaded portion of the pull bolt.

[0004]

However, when the thread of the taper shank portion and the threaded portion of the pull bolt is a triangular thread, the outer peripheral surface of the tip end portion of the taper shank portion is caused by the radial component force of the tightening force of the pull bolt. There is a problem that the taper shank portion slightly expands and the entire outer peripheral surface of the taper shank portion does not evenly contact when the taper shank portion is fitted into the taper shaft hole of the main shaft.

Conventionally, such a degree of expansion of the tip of the tapered shank has not been a problem, but in the case of a machine tool that performs high-precision and high-rigidity machining by rotating a tool at a high speed, that degree of expansion does not occur. Even if the adhesion is deteriorated, the machining accuracy is adversely affected by fine chattering of the tool holder, which is a serious problem to be solved.

In view of the above-mentioned conventional problems, the present invention aims at proposing a tool holder capable of high-speed, high-precision and high-rigidity machining, in which the tip of the tapered shank portion does not expand due to screwing of a pull bolt. And

[0007]

In order to achieve the above-mentioned object, the present invention shows a taper shank portion 3 fitted in a taper shaft hole 12 of a main shaft 11, if indicated by reference numerals in the drawings. And a tool holder 1 including a pull bolt 6 fixed to the tip of the taper shank portion 3 by screwing and connected to a holder retracting means arranged in the main shaft 11, a taper shank portion 3 and a pull bolt 6 are screwed together. The configuration is such that the screw of the part is a sawtooth screw 7 or a square screw.

[0008]

In the present invention, since the screw of the taper shank portion 3 and the screw portion of the pull bolt 6 is the sawtooth screw 7 or the square screw, the tightening force of the pull bolt 6 is as shown by the arrow in FIG. Since it acts in the axial direction and does not generate the radial component force, the tightening force acts in the axial direction at the tip of the tapered shank portion 3 by the screw fixing of the pull bolt 6 as shown by the arrow in FIG. However, since the radial component force is not received, the tip portion does not expand, and therefore the entire surface of the tapered shank portion 3 evenly adheres to the tapered shaft hole 12 of the main shaft 11, The decrease in adhesion does not adversely affect the processing accuracy during high-speed processing.

[0009]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A tool holder according to an embodiment of the present invention will be described below with reference to FIGS.

In FIG. 1, 1 is a tool holder,
A taper shank portion 3 is provided so as to project from one end of the flange portion 2 in the central portion, and a tool gripping portion 5 for holding a tool 4 is provided at the other end side thereof. Reference numeral 2a is a manipulator holding groove formed in the flange portion 2. A pull bolt 6 is screwed and fixed to the tip of the tapered shank portion 2.

As shown in detail in FIG. 2, the pull bolt 6 is provided with an enlarged engagement portion 6c on one end side in the axial direction from the flange portion 6a via a shaft portion 6b and a fitting portion 6d on the other end side.
A threaded portion 6e is provided via a screw thread 6e, and the threaded surface 6a of the threaded portion 6e is a right angle with respect to the axial direction, and the other surface 7b is a sawtooth screw 7 of 45 °.

Corresponding to the pull bolt 6, a fitting hole 8 into which the fitting portion 6d is fitted and a screw hole 9 into which the screw portion 6e is screwed are formed at the axial center position of the tip of the tapered shank portion 3. The screw hole 9 is composed of a 45 ° sawtooth screw corresponding to the sawtooth screw 7.

Reference numeral 11 denotes a main shaft of a machine tool, and a taper shaft hole 12 for fitting and fixing the taper shank portion 3 of the tool holder 1 is formed at a shaft center position of a tip end portion thereof. Further, holder pull-in means (not shown) which is connected to the pull bolt 6 and pulls in the tapered shank portion 3 in the main shaft 11.
Is decorated.

In the above structure, when the tapered shank portion 3 of the tool holder 1 is inserted into the tapered shaft hole 12 of the main shaft 11, the holder retracting means (not shown) incorporated in the main shaft 11 is connected to the pull bolt 6. By pulling this in, the tapered surface of the tapered shank portion 3 and the inner peripheral surface of the tapered shaft hole 12 on the main shaft 11 side come into close contact with each other, and the tool holder 1 is attached to the main shaft 11.

By the way, the taper shank portion 3 of the tool holder 1 is often ground with a pull bolt 6 fixedly screwed therein for high-speed and high-precision machining. In that case, the taper shank portion 3 is used. Is precision finished. However, the pull bolt 6 is worn out more than the main body of the tool holder 1, so that it may be replaced frequently.
When the pull bolt 6 thus exchanged is screwed and fixed to the taper shank portion 3, the screwing of both is conventionally performed by the 60 ° triangular screw on the receiving surface of the screw thread and the surface opposed thereto. When the taper shank is strongly screwed, a radial component force acts on the screwing portion of the taper shank portion 3, and the tip end portion of the taper shank portion slightly expands due to this component force, which removes this expansion component. Therefore, it is necessary to re-polish the tapered shank portion every time the pull bolt 6 is replaced.

However, in the embodiment of the present invention, the pull bolt 6
Since the threaded portion 6e of the pull screw 6 is constituted by the sawtooth screw 7 and the receiving surface 7a for receiving the tightening force at the time of screwing is formed at right angles to the axial center direction, the tightening force of the pull bolt 6 is indicated by the arrow in FIG. Since it acts in the axial direction and does not generate a radial component force as shown in FIG. Since only the tightening force in the axial direction as shown is exerted and no component force is applied in the radial direction, the tip portion does not expand, and therefore, even if the pull bolt 6 is replaced, the main shaft 11 is replaced. The entire surface of the tapered shank portion 3 is evenly adhered to the tapered shaft hole 12 and the adhesion is not deteriorated, which does not adversely affect the processing accuracy during high-speed processing.

Further, the threaded portion 6e of the pull bolt 6 and the threaded portion 9 of the taper shank portion 3 with which the pull bolt 6 is screwed are not necessarily limited to the sawtooth screw, and the point is that the receiving surface of the screw thread which directly receives the tightening force. Any screw can be used as long as it is perpendicular to the axial direction, and the screw portions 6e and 26 may be square screws as shown in an enlarged view in the circle on the right side of FIGS.

The fitting portion 6a of the pull bolt 6 and the fitting hole 8 at the tip of the tapered shank portion 3 into which the pull bolt 6 is fitted constitute a so-called spigot fitting, which can contribute to radial centering. .

Next, a comparative experiment conducted on the present invention and the conventional example will be described. As an alternative to the tool holder of the present invention, a test bar 21 as shown in FIG. 3 was produced, and the pull bolt 6 was screwed and fixed to the taper shank portion 22 formed at one end thereof. That is, at the axial center position of the tip of the taper shank portion 22, a fitting hole 23 into which the fitting portion 6d fits and a screw hole 24 into which the screw portion 7e is screwed are formed, and the screw hole 24 corresponds to the saw tooth screw 7. Serrated screw 2
It is composed of 5.

In the experiment, the pull bar 6 was screwed and fixed to each of the test bar 21 and the conventional tool holder with a predetermined tightening torque, and then the outer peripheral surface of the taper shank portion 22 was ground. Then, the taper contact surface measurement and the strain measurement of the outer peripheral surface of the taper shank portion 22 using an electric micrometer were performed for each of the state in which the pull bolt 6 was removed and the state in which the pull bolt 6 was attached again. Tightening torque is 250kg-cm, 300
An experiment was conducted for each of kg-cm and 350 kg-cm. Further, the taper contact surface measurement is performed by using BIG-KURODA NT30 No. 2727
Was used as a brew. The electric micrometer is Marvos MODEL.
The E4 duplex system was used.

The test results of the test bar according to this example are shown in Table 1, and the test results of the conventional example are shown in Table 2.

[0022]

[Table 1]

[0023]

[Table 2]

From these tables, it is natural that after polishing, in both the present example and the conventional example, brewing was 100%.
The strain is 0, but with the pull bolt removed, the brew is 60 to 70% when the tightening torque is 250 kg and 30 to 30% when the tightening torque is 300 kg to 350 kg in this embodiment.
Although it is 50%, it cannot be measured in the conventional example, and the strain is −1.5 to −2.5 μm in the present embodiment, whereas it is −3.5 to −6.5 μm in the conventional example, and again. With the pull bolt attached, the brew is 70 in this embodiment.
%, But it was impossible to measure in the conventional example, and the strain was 3 to 5 μm in contrast to the range of −1 to 1.0 μm in this example.

Further, after the pull bolt 6 was ground to the taper shank portion 22 without being screwed and fixed, the pull bolt 6 was attached at 250 kg-cm, then changed at 300 kg-cm, and further changed at 350 kg-cm. For the case, the taper contact surface measurement and the strain measurement of the outer peripheral surface of the taper shank portion 22 using an electric micrometer were similarly performed. Table 3 shows the experimental results of the test bar according to this example, and Table 4 shows the experimental results of the conventional example.

[0026]

[Table 3]

[0027]

[Table 4]

In Tables 3 and 4, the brew is 70% or more in this embodiment, but cannot be measured in the conventional example, and the strain is 3 to 3 in contrast to the distortion of 1 to 2 μm in this embodiment. It became 7 μm.

From the above experimental results, it can be seen that the present invention exerts a great effect.

Although the saw-tooth screw 7 is used in the above embodiment, the same effect can be obtained by using a square screw.

[0031]

According to the present invention, since the screw of the taper shank portion and the screwing portion of the pull bolt is a sawtooth screw or a square screw, the tightening force of the pull bolt acts in the axial direction, and the component force in the radial direction is reduced. Since it does not occur, the tip of the taper shank does not expand due to the screw fixing of the pull bolt.Therefore, the entire surface of the taper shank comes into uniform contact with the taper shaft hole of the main shaft, resulting in uneven contact. It is possible to reliably prevent that the processing accuracy is adversely affected during high-speed processing due to the state.

Therefore, when it is necessary to replace the pull bolt due to long-term use, it is only necessary to screw the new replaced pull bolt into the tapered shank portion.
There is an advantage that it is not necessary to re-machine the tapered shank portion as in the conventional case.

[Brief description of drawings]

FIG. 1 is a partial sectional front view of a tool holder according to an embodiment of the present invention mounted on a spindle.

FIG. 2 is a front view of the pull bolt of the embodiment and a partially enlarged sectional view thereof.

FIG. 3 is a partial sectional view of a test bar used in an experiment and a partially enlarged sectional view thereof.

[Explanation of symbols]

 1 Tool Holder 3 Tapered Shank Part 6 Pull Bolt 7 Sawtooth Screw 11 Spindle 12 Tapered Shaft Hole

Claims (1)

[Claims] 1. A taper shank portion fitted in a taper shaft hole of a main shaft, and a pull bolt screwed and fixed to a tip of the taper shank portion and coupled to a holder retracting means arranged in the main shaft. In the tool holder described above, the screw of the taper shank portion and the screwing portion of the pull bolt is a sawtooth screw or a square screw.