JP2012245580A - Broach - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a broach that prevents damage to a cutting blade, and whose service life is easily determined, while reducing the number of manufacturing man-hours and a manufacturing cost of the broach.SOLUTION: The broach 1 includes a roughing part 10 and a finishing part 20. Land widths 201a, 202a, 203a of cutting blades 201, 202, 203 of the finishing part 20 are gradually reduced toward a final cutting blade 300 side of the broach 1. Land widths 101a, 102a, 103a of the cutting blades 101, 102, 103 of the roughing part 10 may be gradually increased toward the finishing part 20. Further, blade groove widths 201b, 202b, 203b between the cutting blades 201, 202, 203 of the finishing part 20 may be reduced toward the final cutting blade 300 side of the broach 1, while being increased and decreased.

Description

  The present invention relates to a broach that mainly cuts internal gears, spline holes, and the like.

With conventional broaches, the wear of the cutting edge progresses as the number of workpieces processed by cutting (broaching) increases, so the cutting edge of the cutting edge is polished each time the cutting edge sharpness decreases (hereinafter referred to as rake face polishing). By increasing the number of workpieces that can be broached, the life of the broach was extended. Rake face polishing involves polishing a certain amount of the rake face from the cutting edge where wear is progressing to the final cutting edge in the finishing part of the broach, so the land width of the cutting edge gradually increases as the number of polishing increases. Becomes smaller.

Therefore, if the cutting edge of the broach has a double angle, the larger diameter (dimension) or smaller diameter (dimension) or overball dimension (overpin dimension) of the broach decreases as the number of rake face polishing increases. There is a problem that the broach reaches the end of its life if the workpiece cannot be processed according to the predetermined dimensions. That is, the cause of the life of the broach was that the land width of the cutting edge of the broach decreased with the rake face polishing.

Therefore, in Patent Document 1, the land width of the final cutting edge in the finishing processing portion of the broach is made larger than the land width of other cutting blades. Specifically, the land width of the final cutting edge is set to another cutting blade in the finishing processing portion. A broach capable of increasing the number of times of rake face polishing and extending the life by setting the land width to 1.2 to 1.6 times the width is disclosed.

Japanese Patent No. 3770816

However, in the broach of Patent Document 1, only the land width of the final cutting edge is larger than the land width of the other cutting edges. Therefore, when the second angle of the cutting edge of the finishing portion is constant, as described above. The larger diameter (dimension), smaller diameter (dimension), or overball dimension becomes smaller as the number of rake face polishing increases (it becomes smaller than the diameter of the broach before the start of machining), and it becomes impossible to process according to the specified dimension. The broach reaches the end of its life. Therefore, it is necessary to make the second angle of the final cutting edge of the broach smaller than the second angle of the other cutting edges so that the large diameter (dimension), small diameter (dimension), or overball dimension does not become small.

However, if the second angle of the final cutting edge of the broach is made smaller than the second angle of the other cutting edges, the amount of cutting of the final cutting edge in the finishing part will be increased by rake face polishing, and finishing will be performed during broaching. As a result of excessive load applied to the final cutting edge of the part, there was a problem that the cutting edge was eventually damaged.

In addition, in order to increase the number of rake face polishing in the same broach as much as possible, increasing the number of cutting blades in the broach finishing part can sufficiently secure the number of cutting edges that can be involved in broaching. Increasing the number of cutting blades in the section results in a problem that the length of the broach becomes longer than necessary, and the man-hour and cost for producing the broach increase.

Accordingly, in view of the above-described problems, the present invention has an object to provide a broach that can prevent damage to the cutting blade and easily determine the life while reducing the man-hours and cost of manufacturing the broach. .

  In order to solve the above-described problem, in the present invention, a broach having a roughing portion and a finishing portion, and the land width of each cutting edge of the finishing portion approaches the final cutting edge of the broach. It was decided to provide a gradually decreasing brooch. According to the present invention, it is possible to increase the number of cutting edges of the finished processing portion without changing the broach length by the length corresponding to the reduced land width as a whole broach. Also, since the land width is larger on the first cutting edge side of the finishing section and the land width is smaller on the final cutting edge side, when the life of the broach is approaching, each cutting in the roughing section and finishing section used for broaching is performed. The blade land width is almost uniform.

The broach according to the present invention includes a roughing portion where each cutting edge sequentially performs roughing on a workpiece, and a finishing portion where each cutting edge sequentially performs finishing processing on a target dimension of the workpiece. Is more arranged. The finishing part has a plurality of cutting edges, and the land width of these cutting edges gradually decreases from the first cutting edge side to the final cutting edge (which is also the final cutting edge of the broach) of the finishing part. is doing. That is, each cutting edge of the finish processing portion has a configuration in which the land width is larger toward the first cutting edge and the land width is smaller toward the final cutting edge.

Further, as an aspect in which the land width gradually decreases, the land width is reduced at a constant rate for each interval between the cutting edges, as the change in the land width from the first cutting edge side to the final cutting edge side of the finish processing portion. A linear decrease, a curvilinear decrease in which the land width decreases between each cutting edge, or several cutting edges as one section, and the land width is constant within the same section, but the land width for each section It can be a gradual decrease in which becomes smaller.

In the invention which concerns on Claim 2, it was set as the broach which increased gradually as the land width of each cutting blade of a roughing part approached a finishing process part. That is, the broach according to the present invention is a broach having a land width that is larger as the cutting edge is closer to the boundary between the finish processing portion and the roughing portion, and a land width that is closer to both ends of the broach. As a result, the number of cutting edges in the roughing portion of the broach can be increased by an amount corresponding to the reduced length of the land at the leading end portion of the broach (the leading end portion of the roughing portion).

In the invention which concerns on Claim 3, it was set as the broach which became small, increasing and decreasing as the groove width between each cutting blade of a finishing process part approaches the last cutting blade side of a broach. As a result, the resonance phenomenon between the broach and the workpiece that is generated by broaching is suppressed.

As described above, the present invention is a broach in which the land width of each cutting edge of the finish processing portion gradually decreases as it approaches the final cutting edge of the broach, so that the land width of the entire broach is reduced by the corresponding length. Since it is possible to increase the number of cutting edges in the finished processing portion without changing the broach length, it is possible to reduce the man-hours and costs for producing the broach. Also, since the land width is larger on the first cutting edge side of the finishing section and the land width is smaller on the final cutting edge side, each cutting edge in the roughing section and finishing section used for broaching is approached as the life of the broach approaches. Since the blade land widths are substantially uniform, the life (use limit) of the broach can be easily visually determined.

Further, in the invention according to claim 2, since the land width of each cutting edge of the roughing portion is gradually increased as it approaches the finishing processing portion, the number of cutting edges in the roughing portion of the broach can be increased. Regardless of the specifications of the broach, the total number of cutting edges of the broach can be increased without changing the broach length.

Furthermore, in the invention according to claim 3, the resonance between the broach and the workpiece is achieved by using a broach in which the width of the groove between the cutting edges of the finishing portion is increased and decreased as it approaches the final cutting edge side of the broach. Since the phenomenon is suppressed, sufficient processing accuracy can be ensured even for a hard workpiece (high hardness material).

In addition, by making all the second corners of all the cutting edges constituting the roughing part and finishing part of the broach according to the present invention the same angle, the height between the cutting edges can be increased even if the number of rake face polishing increases. Since the difference is almost equal, it is possible to prevent damage to the cutting edge due to an excessive load (cutting resistance) during broaching.

It is a side view of the whole broach 1 concerning the present invention. It is the elements on larger scale of the finishing part 20 of the broach 1 shown in FIG. It is the elements on larger scale of the rough processing part 10 of the broach 1 shown in FIG.

  An example of an embodiment of the present invention will be described with reference to the drawings. 1 is a side view of the entire broach 1 according to the present invention, FIG. 2 is a partially enlarged view of a finishing portion 20 of the broach 1 shown in FIG. 1, and FIG. 3 is a partially enlarged view of a roughing portion 10 of the broach shown in FIG. It is.

As shown in FIG. 1, the broach 1 according to the present invention includes a roughing unit 10 that first performs broaching on a workpiece and a finishing unit 20 that performs processing for adjusting the workpiece to a final finish dimension. It has become. Broaching is performed in a state where a key groove (not shown) at the end 30 of the broach 1 is fitted into the connection fixing portion of the broaching machine.

As shown in FIG. 2, the finish processing unit 20 includes cutting edges 201, 202, 203... And has land widths 201 a, 202 a, 203 a. It gradually decreases as it approaches one final cutting edge 300. Moreover, the blade groove width 201b, 202b, 203b ... between adjacent cutting blades is provided, and it becomes small, increasing / decreasing as the final cutting blade 300 of the broach 1 is approached.

As shown in FIG. 3, the roughing portion 10 is composed of cutting edges 101, 102, 103..., And there are land widths 101a, 102a, 103a. It gradually increases as it approaches the processing unit 20.

In order to compare the lifespan of the broach according to the present invention and the conventional broach, a broaching test was performed under the processing conditions described later, and the test results will be described. As shown in FIG. 1, the broach used in this test is composed of a roughing section 10 having eight cutting edges and a finishing section 20 having 13 cutting edges (including the final cutting edge of the broach). It is the broach 1 currently formed. The land widths 201a, 202a, 203a of the cutting edges 201, 202, 203 of the finish processing unit 20 are gradually reduced toward the final cutting edge 300 side, and the blade groove width 201b between the cutting edges 201, 202, 203, 202b and 203b become small, increasing / decreasing as it approaches the final cutting edge 300 side. In addition, the land widths 101 a, 102 a, and 103 a of the cutting edges 101, 102, and 103 of the rough machining unit 10 are configured to gradually increase as the finish machining unit 20 is approached. The broach according to the present invention has an outer diameter (overball pin size) of 44 mm and a broach length of 250 mm.

On the other hand, the conventional broach is formed of a roughing portion having 7 cutting edges and a finishing portion having 12 cutting edges (including the final cutting edge of the broach). The outer diameter (overball pin dimension) of the conventional broach is 44 mm, which is the same diameter as the broach according to the present invention, and the broach length is 250 mm, which is the same length as the broach according to the present invention. In addition, the land widths of the cutting edges of the finishing and roughing parts are all the same, and the widths of the blade grooves between the cutting edges of the finishing part are also the same.

In this test, broaching was performed under the processing conditions of processing speed: 60 m / min, lubricant: mist coolant with vegetable oil, workpiece material: carburized and hardened steel (SCM420). In addition, while performing rake face polishing of the cutting edge of the broach when a predetermined processing accuracy could not be ensured, evaluation was performed based on the number of rake face polishing possible until final disposal (up to the service life). As a result, the broach according to the present invention can be ground 15 times, and the workpiece machining accuracy can be secured to a predetermined dimension. In contrast, the number of times that the conventional broach can be raked is 13 times. As described above, the broach according to the present invention can realize a longer life of the broach without changing the length of the broach as compared with the conventional broach.

In the case of rake face polishing of the broach according to the present invention, not all the cutting edges of the broach are uniformly rake-polished regardless of the rake face polishing frequency, but every time the rake face polishing frequency is increased. Rake face polishing is performed while the number of cutting edges of the roughing portion to be used for polishing is sequentially reduced from the first cutting edge side of the broach one by one. For example, in the first rake face polishing, the first cutting edge of the roughing section 10 from the final cutting edge 300 side of the finishing section 20 shown in FIG. 1 (also the first cutting edge of the broach 1 according to the present invention). Rake surface polishing is performed for cutting blades up to 101. In the second rake surface polishing, cutting blades from the final cutting blade 300 side of the finish machining unit 20 to the second cutting blade 102 of the rough machining unit 10 are targeted. In the third rake face polishing, rake face polishing is performed on the cutting edges from the final cutting edge 300 side of the finishing part 20 to the third cutting edge 103 of the roughing part 10.

Regardless of the number of times of rake face polishing, if all the cutting edges of the broach 1 are uniformly rake-polished, the rake face of the broach 1 is more polished as the cutting edge of the roughing portion 10, particularly the cutting edge that performs broaching first. As the number of times increases, the land width of the cutting edge decreases, and finally the large diameter (dimension), small diameter (dimension) or tooth thickness of the broach 1 becomes smaller than the dimension of the workpiece before broaching. Therefore, for the broach according to the present invention, the rake face polishing prevents the cutting edge tooth thickness of the roughing part from becoming smaller than that of the workpiece before broaching, thus preserving its role as a cutting edge. Therefore, rake face polishing is performed by the method (procedure) described above.

DESCRIPTION OF SYMBOLS 1 Broach 10 Roughing part 20 Finishing part 101, 201 (1st) Cutting edge 102, 202 (2nd) Cutting edge 103, 203 (3rd) Cutting edge 101a, 102a, 103a Each cutting edge of a roughing part Land widths 201a, 202a, 203a Land widths 201b, 202b, 203b of each cutting edge of the finish machining part Blade groove width 300 between each cutting edge of the finishing part 300 Final cutting edge

Claims (3)

  A broach having a roughing portion and a finishing portion, wherein the land width of each cutting edge of the finishing portion is gradually reduced toward the final cutting edge side of the broach. 2. The broach according to claim 1, wherein a land width of each cutting edge of the roughing portion gradually increases as the finish processing portion approaches. 3. The broach according to claim 1, wherein the width of the groove between each cutting edge of the finish processing portion is reduced while increasing or decreasing as it approaches the final cutting edge side of the broach.

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