JP2001113412A - Internal broach - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an internal broach capable of processing a large quantity of materials of hardness exceeding HRC 45 in conditions of suppressing occurrence of pitching and maintaining stable process dimensions by improving construction of broach cutting edges, and of reducing process man-hour by eliminating incidental heat treatment process and reforming process that are conventionally required. SOLUTION: In an internal broach provided with a series of cutting edge group cutting an internal surface of round hole, square hole, spline hole, serration hole or the like, a rake angle of a cutting edge of the broach is set more than or equal to -18 deg. and less than or equal to +10 deg., and TiAlN coating is applied on whole surface of the cutting edge, and a cutting edge pitch P of each cutting edge group of the broach maintains a relation of P<=1.2√L in case that a cutting length is defined as L, for processing hard materials of hardness equivalent to HRC 35-55.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a broach used for forming an inner surface of a round hole, a square hole, a spline hole, a serration hole and the like, and more particularly to a broach suitable for cutting a high-hardness workpiece.

[0002]

2. Description of the Related Art A general single-piece broach is provided with a series of cutting blades including cutting blades, semi-finishing blades, and finishing blades, each having a different cutting depth. Thus, the processing can be completed, which is suitable for a mass production process of molded articles. In particular, in the inner surface processing, a deformed shape which cannot be handled by other processing methods can be easily formed, and excellent processing dimensions and finished surface roughness can be obtained without requiring skill in work. Such features can be obtained by appropriately configuring the shape, arrangement, and the like of the cutting edge in accordance with the workpiece. Be restricted. Workpieces suitable for broaching generally have a hardness of less than HRC20,
Up to about 30 are in practical use. However, recently, the hardness of a workpiece tends to increase, and this has been dealt with by coating or the like. For example, Japanese Patent Application Laid-Open No. Hei 7-195228 discloses a coated H-coated cutting edge having a twist.
A broaching tool for machining a hard material equivalent to RC 35 to 55 is shown.

[0003]

As described above, the hardness of the conventional workpiece is about HRC 20 to 30, and the workpiece having a hardness exceeding HRC 45 cannot be subjected to the inner surface broaching. was there. This is because, in addition to the reason that it is difficult to increase the strength of the main body in the inner broach, the cutting edge cannot be twisted, so cutting must be intermittent, and chipping of the cutting edge occurs early. The main reasons are that the tool life is short and the machining dimensions vary, making it impossible to obtain correct accuracy. For this reason, there is a problem that a large number of steps are required for such a material having such hardness, for example, tempering is performed in advance to reduce the hardness, broaching is performed, and quenching is performed again after processing. However, even with this method, there is a problem that the thermal dimensional change accompanying quenching after processing is large and the processed dimensions are still unstable. Therefore, there has been a problem that even straightening is required, and the number of man-hours is further increased.

[0004]

SUMMARY OF THE INVENTION The present invention has been made in view of the above background. By improving the configuration of the cutting edge of the broach, chipping can be performed even on a workpiece having a hardness exceeding HRC45. The purpose of the present invention is to provide an inner broach that can process a large number of workpieces in a state where the processing dimensions are stable while suppressing the occurrence of machining, and eliminates the necessary additional tempering and straightening processes, thereby shortening the processing man-hours. And

[0005]

SUMMARY OF THE INVENTION In order to achieve the above object, the present invention provides an inner surface broach having a series of cutting blades for cutting the inner surface of a round hole, a square hole, a spline hole, a serration hole, and the like. The rake angle of the cutting edge of the broach is -1
8 ° or more and + 10 ° or less, and Ti
When an AlN coating is applied and the cutting edge pitch P of each cutting edge group of the broach is a cutting length L, P ≦ 1.
2√L, which is used for processing a high-hardness workpiece having a hardness of 35 to 55 HRC.

[0006]

First, by applying the present invention, the rake angle of the cutting edge of the inner broach is set to -18 ° or more and +
Since the angle is reduced to 10 ° or less, the angle of the blade between the rake face and the flank becomes large, the strength of the cutting edge is increased, and it is possible to withstand chipping. The rake angle is set to -18 ° or more because if it is less than this, the increase in cutting resistance cannot be ignored, and if it is less than + 10 °, the strength becomes insufficient when it exceeds this, and chipping or the like is likely to occur. To become-
18 ° or more and + 10 ° or less.

Second, in the present invention, since the TiAlN coating is applied to the entire surface of the cutting edge of the inner broach, the cutting edge is protected by the film, so that chipping can be reduced and stable processing accuracy can be maintained. That is, in the present invention, since the edge angle of the cutting edge is large, an edge effect is difficult to be obtained, and a smooth film is obtained. Also, since the rake angle is small, the rake surface has a uniform thickness with other surfaces such as a flank. It can protect the cutting edge and exhibit a remarkable effect for cutting hard materials. Hitherto, the coating applied to the broach has been used as a means for suppressing the friction of the cutting edge work on the flank surface or the flank surface and the side surface. Although the blade portion is not preferred because the film easily becomes thicker by obtaining an edge effect and the film is easily peeled off, the effect can be led by limiting the blade shape and application as in the present invention. You can. The reason why the coating composition of the coating is limited to TiAlN is that the pressure resistance of the coating is greater than other coating compositions and the oxidation resistance is excellent, so a large lubricating effect can be expected. This is because a remarkable effect is obtained. The broach whose tool life has expired can be regenerated by re-grinding, but in the present invention, the film is removed and re-coated after re-grinding. This means that a new coating is reproduced, and the tool life is guaranteed for each regrind. Since the coating is applied to the entire surface of the cutting edge, the film present on the rake face has the effect of reducing the friction between the chip and the rake face to reduce the cutting resistance. When designing an inner surface broach with limited body strength, it is essential to keep the cutting resistance low, and reduce the rake angle for materials with high specific cutting resistance, such as hardened materials. However, since the cutting force is increased, it cannot be said that it is contrary to the requirement, but the cutting force does not increase particularly by the above-mentioned effect.

Third, in the inner surface broach, when the cutting edge pitch P of each cutting edge group is L and the cutting length is L, P ≦ P
1.2√L. In broach design, the relationship between the cutting edge pitch P and the cutting length L is known, and P = (1.25 to 2) ２L is usually selected. Here, a relatively small value is recommended for the inner surface broach, but in the present invention, a smaller value is used. That is, in the present invention, since the rake angle is reduced, the undercut of the rake face can be reduced accordingly,
Further, since the entire cutting edge is coated and has a sufficient lubricating effect, the cutting edge pitch is small, and therefore the cutting edge strength can be maintained even if the blade thickness is small. This means that the number of blades can be increased for the same overall length, and has the effect of reducing the cutting amount of one blade in the cutting of hardened material to adjust the cutting resistance.

As described above, according to the present invention, even when the workpiece is a hard material, the occurrence of chipping can be suppressed, the state of stable processing accuracy can be maintained, and a large number of workpieces can be processed. To In addition, this makes it possible to eliminate the tempering work before and after the broaching, which has become common sense in the conventional broaching of high-hardness materials, and can omit all the man-hours required for this. This is a remarkable effect of being able to do so. Hereinafter, the present invention will be described based on examples.

[0010]

1 to 3 show a spline broach for machining an involute spline hole of an automobile part to which the present invention is applied. This brooch has a maximum diameter of 25.6 mm and a total length of 1
000 mm, spline tooth shape between pin diameter 2
It is 1.3 mm and has 53 spline cutting blades and 5 spline finishing blades at the front, and 8 round blades and 5 round finishing blades at the rear. The rake angle is 0
゜, the cutting edge pitch is 7mm, and Ti
AlN coating is applied.

As in the process of FIG. 4, in the example of the present invention, the processing of a high-hardness material can be carried out.
It can be tempered to RC40-55 and broached. In contrast, FIG. 5 shows a conventional process. After tempering, only the hole is tempered to HRC25,
Broaching is performed, and after broaching, partial quenching is again performed by induction hardening in order to recover strength.

FIGS. 6 and 7 show the results of the number of processing and the dimensional change.
Shown in Compared to the conventional method of FIG.
Not to mention 000 parts, cutting was still possible even if 2,000 parts were processed as in the past. FIG. 6 shows a comparison of the cutting edge wear between the product of the present invention and the conventional product. The wear of the conventional product increases with the number of processes, whereas the product of the present invention has a slight Met. This is also reflected in the processing accuracy shown in FIG. 7, and when the spline accuracy was evaluated using the between pin diameter,
It was a stable state with almost no change from the initial stage after 2,000 cuttings.

As described above, it is possible to omit all of the tempering step and the induction quenching step which have been required so far, and it is possible not only to realize a remarkable reduction in the steps but also to contribute to an increase in the number of processed parts. By applying the present invention, TiAlN is used as a coating material, so that the coating has a high pressure resistance, has excellent oxidation resistance and can be expected to have a lubricating effect, and also has a high speed tool steel which is a material of a broach. Since the affinity is good, peeling of the film is unlikely to occur,
This is because the cutting edge is protected for a long period of time, and a remarkable effect is obtained for processing hard materials.

[0014]

As described above, according to the present invention, HRC4
Even if the workpiece has a hardness of more than 5, a large number of workpieces can be machined in a state where the machining dimensions are stable, and it is possible to obtain an inner broach capable of achieving a reduction in man-hours by eliminating ancillary processes required so far. did it.

[Brief description of the drawings]

FIG. 1 is a front view of a spline broach with a round blade according to an embodiment of the present invention.

FIG. 2 is a partially enlarged view illustrating the configuration of the blade of FIG. 1;

FIG. 3 is a view for explaining a blade-shaped configuration of the cutting blade of FIG. 2;

FIG. 4 shows steps for explaining a processing procedure of a high-hardness workpiece.

FIG. 5 shows steps for explaining a processing procedure of a conventional high-hardness workpiece.

FIG. 6 shows a comparison of cutting edge wear between the present invention example and the conventional example.

FIG. 7 shows a comparison of the change in between pin diameters.

FIG. 8 shows a schematic diagram illustrating the workpiece and the diameter of the between pin.

[Explanation of symbols]

 1 Body 2 Cutting edge 3 Rake angle 3 Rake angle in case of negative angle 4 Cutting edge pitch 5 Between pin diameter 6 Workpiece 7 Between pin diameter measuring pin

Claims (1)

[Claims] 1. An inner surface broach having a series of cutting edges for cutting the inner surface of a round hole, a square hole, a spline hole, a serration hole, etc., wherein the rake angle of the cutting edge of the broach is -1.
8 ° or more and + 10 ° or less, and Ti
When an AlN coating is applied and the cutting edge pitch P of each cutting edge group of the broach is a cutting length L, P ≦ 1.
An inner surface broach having a relationship of 2√L and being used for processing a high-hardness workpiece having a hardness of 35 to 55 HRC.