JPH1043943A - Method of grinding female screw for hard and brittle materials, and tool used therefor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To significantly reduce the machining time by successively performing preliminary grinding and finish grinding onto the circumferential surface of a prepared hole in the axial moving operation within the prepared hole of a hard and brittle material of a cutting tool to be spirally moved while being rotated at high speed. SOLUTION: A female screw grinding tool is spirally moved in an arrowed direction B while being rotated at high speed in an arrowed direction A and inserted into a prepared hole 7, and a desired female screw is ground on the circumferential surface of the prepared hole 7 by up cutting by one axial moving operation within the prepared hole 7 of the female screw cutting tool. The female screw cutting tool has a protruding sectional ring form the height of which becomes gradually smaller than the groove depth of the desired female screw from a finish grinding part 3 toward one and direction of a shank part 1, and the same pitch as the pitch of the desired screw. A preliminary grinding and a finish grinding are subjected to the female screw of the prepared hole 7 by a preliminary grinding part 5 and the finish grinding part 3.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for grinding an internal thread of a hard and brittle material in which a female thread is ground on a peripheral surface of a prepared hole of a hard and brittle material such as alumina, quartz glass, silicon carbide, aluminum nitride, and silicon nitride. And a tool used for the same.

[0002]

2. Description of the Related Art Conventionally, as a method for grinding an internal thread of a hard and brittle material of this type, a moving operation in the axial direction in which a grinding tool is rotated in a prepared hole of a hard and brittle material at a high speed and in a spiral motion is repeated several times. A method of grinding an internal thread on the peripheral surface of a hole is known, and as a tool used for this, for example, as shown in FIG. It is known that a grinding portion 32 made of one diamond grindstone having a ring shape with a corresponding convex cross-sectional shape is provided. The diamond grindstone is usually formed by electrodepositing diamond abrasive grains on a ring-shaped portion having a convex cross-section provided integrally with one end of a shank portion 31 made of tool steel in accordance with a valley shape of a female thread (electroplating method). Method of fixing the grains).

[0003]

However, in the conventional method for grinding internal thread of hard and brittle material, heavy grinding cannot be performed, and the operation of axially moving the grinding tool in a spiral motion while rotating at high speed must be repeated several times. Therefore, there is a problem that the processing time is long. In addition, in the case of a conventional hard and brittle material female thread grinding tool, since there is only one ring-shaped diamond grindstone as the grinding part and the tool life is short, variation in the diameter at the entrance and exit of the female thread hole is observed. In addition, there is a problem that processing accuracy is poor and finishing processing is required. Accordingly, an object of the present invention is to provide a method for grinding female threads of hard and brittle materials and a tool used for the female thread, which can greatly reduce the processing time, extend the useful life, and eliminate the need for finishing.

[0004]

In order to solve the above-mentioned problems, a method for grinding a female thread of a hard and brittle material according to the present invention is described. Preliminary grinding and finishing on the peripheral surface of the prepared hole in one axial operation of moving the grinding tool, which rotates spirally while rotating at high speed, in the prepared hole of the hard and brittle material when grinding the internal thread on the peripheral surface It is characterized in that grinding is sequentially performed. Further, a hard and brittle material internal thread grinding tool is a hard and brittle material internal thread grinding tool for performing a spiral motion while rotating at high speed in a prepared hole of a hard and brittle material to grind a female screw on a peripheral surface of the prepared hole. A finishing grinding section comprising a number of diamond wheels having a ring shape with a convex cross-sectional shape corresponding to the root shape of the desired female thread and having the same pitch as the desired female thread on the outer periphery of one end of the shank portion; A ring consisting of a large number of diamond grinding wheels having a convex cross-sectional ring shape whose height gradually decreases from the root depth of the desired internal thread as it moves away from the portion toward the one end of the shank portion, and having the same pitch as the desired internal thread The grinding part is provided continuously. It is preferable that the finish grinding unit and the preliminary grinding unit are provided with an axial slit. It is preferable that fine diamond abrasive grains are used for the diamond grindstone in the finish grinding section, and coarse diamond abrasive grains are used for the diamond grindstone in the preliminary grinding section. Further, it is preferable that the diamond grindstone in the finish grinding section is an electrodeposited bond diamond grindstone, and the diamond grindstone in the preliminary grinding section is a metal bond diamond grindstone.

[0005]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a first embodiment of a hard and brittle material internal thread grinding tool according to the present invention. In the figure, reference numeral 1 denotes a shank portion made of tool steel, and an outer periphery of one end portion of the shank portion 1 (a lower end portion in FIG. 1)
It is integrally formed in a ring shape with a convex cross-section following the desired female thread's valley shape, and is electrodeposited with diamond abrasive grains on its surface to have a convex cross-sectional shape corresponding to the desired female thread's valley shape. A finish grinding portion 3 composed of two diamond grinding wheels 2 having the same pitch as the pitch of the screw, and a valley of a desired female thread as the distance from the finish grinding portion 3 toward one end of the shank portion 1 decreases (downward in FIG. 1). It has a ring shape with a convex cross-section whose height gradually decreases from the depth, and has the same pitch as the pitch of the desired internal thread, and three diamond abrasive grains having the same grain size as the diamond grinding stone 2 are electrodeposited. A preliminary grinding unit 5 composed of a diamond grinding wheel 4 is provided continuously. In addition, the adjacent finish grinding unit 3
And the pitch of the diamond grinding wheels 2 and 4 of the preliminary grinding unit 5
Naturally, it is the same as the pitch of the desired internal thread.

In order to form an M8 (metric coarse thread, P1.25 mm) threaded hole in a workpiece made of a hard and brittle material such as alumina ceramics using the female thread grinding tool having the above structure, first, As shown in FIG. 2, in order to prevent chipping of the thread, a prepared hole 7 having a diameter of 6.9 mm, which is larger than that in the case of threading a metal member, is formed in the workpiece 6. Next, while being held by a chuck of a tapping machine (not shown), the screw grinding tool is rotated at a high speed in a direction indicated by an arrow A in FIG. 2 while being spirally moved in a direction indicated by an arrow B in FIG. Then, by a single axial movement operation in the prepared hole of the internal thread grinding tool, a desired internal thread is ground on the peripheral surface of the prepared hole 7 by up-cutting. In the female screw grinding method according to the present invention, the shape and material of the workpiece and the female screw grinding tool are 5,000.
It is preferable to rotate at high speed at a rotation speed of ８8000 rpm. Here, the finish grinding unit 3 in the female thread grinding tool
The outer diameter of the diamond grindstone 2 is close to the diameter of the pilot hole 7, for example, in order to maintain the shape long.
It is preferable to set it to about 8 mm. That is, it is preferable to make the diameter of the pilot hole 7 smaller by 0.1 to 0.2 mm.
Also, the pitch of each diamond grindstone 2, 4 is naturally the same as the pitch of M8. Furthermore, if the spiral movement trajectory is clockwise, the thread is right-handed; if counterclockwise, it is left-handed. Further, the grinding of the female thread may be a down cut.

FIGS. 3 and 4 are a perspective view and a bottom view, respectively, showing a second embodiment of a female thread grinding tool for hard and brittle materials according to the present invention. This internal thread grinding tool is provided with four axial slits 8 at equal intervals in the circumferential direction in the finish grinding section 3 and the preliminary grinding section 5 in order to improve the dischargeability of grinding chips. 3 is provided at a depth reaching the bottom of the valley of the diamond grindstone 2. Since other configurations, functions and effects are the same as those in FIG. 1, the same components and the like are denoted by the same reference numerals and description thereof is omitted.

FIG. 5 is a front view showing a third embodiment of a hard and brittle material internal thread grinding tool according to the present invention. In this female screw grinding tool, in order to further improve the screw precision, the diamond grindstone 2a of the finish grinding section 3 and the diamond grindstone 4a of the preliminary grinding section 5 have different diamond abrasive grains. With two diamond whetstones 2a electrodeposited with fine diamond abrasive grains of # 500 to 800, and the preliminary grinding unit 5 with three diamond whetstones 4a electrodeposited with coarse diamond abrasive grains of # 120 to 230
It is preferable to configure The former particle size is a range for making the internal thread of the workpiece to be the optimum finished surface, and the latter particle size prevents chipping of the abrasive grains (lower limit) and obtains an optimum processing speed ( Range). Since other configurations, functions and effects are the same as those in FIG. 1, the same components and the like are denoted by the same reference numerals and description thereof is omitted.

FIG. 6 is a front view showing a fourth embodiment of the grinding tool for hard and brittle materials according to the present invention. In this female thread grinding tool, in order to further increase the processing accuracy and extend the tool life, the finish grinding section 3 is composed of three diamond grindstones 2b on which the fine diamond abrasive grains are electrodeposited, and the preliminary grinding section 5 is composed of the coarse grains. It is composed of seven diamond whetstones 4b formed by metal bonding diamond abrasive grains. The most preferred particle size of diamond abrasive is the former #
600, the latter being # 170. Since other configurations, functions and effects are the same as those in FIG. 1, the same components and the like are denoted by the same reference numerals and description thereof is omitted.

[0010]

As described above, according to the method for grinding a female thread of hard and brittle material according to the present invention, a desired female thread can be obtained by a single moving operation of the grinding tool. Can be greatly reduced. In addition, according to the internal thread grinding tool of hard and brittle material, the preliminary grinding is performed gradually by the multi-stage diamond grinding wheel of the preliminary grinding unit prior to the grinding of the female thread by the multi-stage diamond grinding wheel of the finish grinding unit. As compared with the above, the service life can be remarkably prolonged, and the finishing accuracy can be eliminated while improving the processing accuracy.

[Brief description of the drawings]

FIG. 1 shows a first example of a tool for grinding a female thread for hard and brittle material according to the present invention.
It is a perspective view which shows embodiment.

FIG. 2 is an explanatory view showing the operation of the female thread grinding tool of FIG. 1;

FIG. 3 shows a second example of the female thread grinding tool for hard and brittle materials according to the present invention.
It is a perspective view which shows embodiment.

FIG. 4 is a bottom view of the internal thread grinding tool of FIG. 2;

FIG. 5 is a diagram showing a third example of a female thread grinding tool for hard and brittle materials according to the present invention.
It is a front view which shows embodiment.

FIG. 6 shows a fourth example of a tool for grinding a hard and brittle material according to the present invention;
It is a front view which shows embodiment.

FIG. 7 is a perspective view of a conventional internal thread grinding tool for hard and brittle materials.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Shank part 2 Diamond grindstone 2a Diamond grindstone 2b Diamond grindstone 3 Finish grinding part 4 Diamond grindstone 4a Diamond grindstone 4b Diamond grindstone 5 Pre-grinding part 6 Workpiece (hard brittle material) 7 Pilot hole 8 Slit

Claims (5)

[Claims] 1. A hard and brittle material for a grinding tool that performs a spiral motion while rotating at a high speed when a grinding tool is spirally moved while rotating at a high speed in a prepared hole of a hard and brittle material to grind an internal thread on a peripheral surface of the prepared hole. A method of grinding a female thread for hard and brittle material, wherein preliminary grinding and finish grinding are sequentially performed on the peripheral surface of the prepared hole in one axial movement operation in the prepared hole. 2. A hard and brittle material internal thread grinding tool for performing a spiral motion while rotating at a high speed in a prepared hole of a hard and brittle material to grind a female screw on a peripheral surface of the prepared hole, wherein an outer periphery of one end of a shank portion is provided. In addition, a finish grinding portion having a ring shape of a convex cross-section corresponding to the root shape of the desired female screw, and comprising a number of diamond grindstones having the same pitch as the desired female screw, and one end direction of the shank portion from the finish grinding portion A pre-grinding part comprising a large number of diamond grindstones having a ring shape with a convex cross section whose height gradually decreases from the valley depth of the desired female thread as it goes away, and having the same pitch as the desired female thread is continuously provided. An internal thread grinding tool for hard and brittle materials. 3. The tool according to claim 2, wherein an axial slit is provided in the finish grinding section and the preliminary grinding section. 4. The hard brittle material according to claim 2, wherein fine diamond abrasive grains are used for the diamond grindstone in the finish grinding section and coarse diamond abrasive grains are used for the diamond grindstone in the preliminary grinding section. Female thread grinding tool. 5. The hard brittle material according to claim 2, wherein the diamond grindstone in the finish grinding section is an electrodeposited bond diamond grindstone and the diamond grindstone in the preliminary grinding section is a metal bond diamond grindstone. Female thread grinding tool.