JP2010046733A - Thread milling cutter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a thread milling cutter capable of improving tool service life by enhancing strength of a cutting edge. <P>SOLUTION: Since a tip 20 is configured of a single crystal diamond, strength of an edge part 30 is enhanced. Accordingly, chipping, wear or the like caused at the cutting edge 31 are suppressed and the tool service life is improved. The change of an edge part shape caused by increase of the number of threadings is reduced so that dimensional accuracy of a female screw is improved. In addition, a cutting surface of a workpiece is smoothly finished so that the strength of the female screw formed at the workpiece is improved. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a thread milling cutter, and more particularly, to a thread milling cutter capable of improving the tool life by increasing the strength of a cutting edge.

  There is a thread milling tool as a tool for cutting a female screw. This is provided with a thread-shaped blade corresponding to the thread groove of the female thread to be formed, and is attached to, for example, an NC milling machine or a machining center, rotated around the axis and revolved in the pilot hole of the workpiece. While being lead-feeded in the axial direction, a female thread is cut on the inner peripheral surface of the prepared hole.

The thread cutting mill described in Japanese Patent Application Laid-Open Nos. 2004-291103 and 2004-291104 is an example thereof, and a tool body rotated around an axis and a tip portion (blade portion) protruding from the tool body toward the outer peripheral side. ) And a thread cutting tip (chip) in which a thread-shaped cutting edge is formed (Patent Documents 1 and 2).
JP 2004-291103 A (paragraph [0021] etc.) JP 2004-291104 A (paragraph [0021] etc.)

  However, in the above-described conventional threaded milling cutter, since the tip is made of a cemented carbide, it is difficult to sufficiently ensure the strength of the cutting edge. For this reason, there has been a problem that the cutting edge is likely to be chipped or worn with threading, and the tool life is insufficient.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a thread milling cutter capable of improving the tool life by increasing the strength of the cutting edge.

  In order to achieve this object, a thread cutting mill according to claim 1 includes a tool body rotated about an axis, and a tip attached to the tool body with a blade portion protruding outward. In addition, the blade portion includes a thread-shaped cutting edge corresponding to the thread groove to be machined, and the tool body is moved relative to the workpiece while being rotated about the axis, An internal thread is cut into the prepared hole of the workpiece by the blade portion, and the tip is made of single crystal diamond.

  According to a second aspect of the present invention, there is provided the thread cutting miller according to the first aspect, wherein the thread shape of the cutting edge is formed by laser irradiation.

  The thread cutting miller according to claim 3 is the thread cutting miller according to claim 2, wherein the tip is made of single crystal diamond which is a hexahedron and each surface has a (100) crystal plane, and the blade portion is a rake face. The ridge line of the flank is defined as the cutting edge, the rake face is constituted by a (100) crystal face, and the ridge line between adjacent flank faces is located on the (100) crystal face.

  The thread cutting mill according to claim 4, wherein the tool body includes a seat surface on which the chip is placed, and the seat surface includes an axis, and the thread of the cutting blade. It is inclined with respect to a virtual plane passing through the top of the shape.

  The thread cutting miller according to claim 5 is the thread cutting miller according to claim 2, wherein the edge of the rake face and the flank face is a cutting edge, and at least a part of the cutting edge is a (111) crystal. Located on the surface.

  According to the thread cutting mill of the first aspect, since the tip is made of single crystal diamond, the strength of the blade portion can be increased. Therefore, chipping or wear generated on the cutting edge can be suppressed, and the tool life can be improved correspondingly.

  In addition, if the wear of the blade can be suppressed, the change in the shape of the blade accompanying the increase in the number of threading operations can be reduced, so the change in the machining accuracy of the workpiece is reduced and the dimensional accuracy of the female screw is improved. There is an effect that can be achieved. The ability to reduce the change in the shape of the blade portion is particularly effective in a thread milling cutter in which the cutting edge shape of the blade portion is transferred as it is as the internal thread shape of the workpiece as in the present invention.

  Furthermore, according to the present invention, since the tip is made of single crystal diamond, the cut surface of the workpiece can be finished smoothly. Therefore, since it is formed on the workpiece, the strength of the screw can be improved.

  According to the threaded milling cutter of claim 2, in addition to the effect of the threading milling cutter of claim 1, it is configured to form the thread shape of the cutting edge by laser irradiation, so that it is difficult to polish single crystal diamond As a result, it is possible to reduce the machining cost.

  In addition, since the (111) crystal plane of single-crystal diamond cannot be processed in the polishing process, when it is necessary to process the (111) crystal plane when forming the thread shape of the cutting edge, It is necessary to perform polishing while adjusting the orientation of the crystal diamond (adjusting the orientation so that the (111) crystal plane does not need to be processed), increasing the processing cost.

  On the other hand, according to the thread cutting mill of the present invention, the thread shape of the cutting edge is formed by laser irradiation. Therefore, even when the (111) crystal plane needs to be processed, the (111) The crystal plane can be melted with a laser to easily form the thread shape of the cutting edge. Therefore, there is no need to perform the operation of adjusting the orientation of the single crystal diamond, and the processing cost can be reduced accordingly.

  According to the threading milling machine of claim 3, in addition to the effect of the threading milling machine of claim 2, the chip is made of single crystal diamond which is a hexahedron and each face is composed of (100) crystal faces, and the rake face is Since the ridge line between adjacent flank faces is located on the (100) crystal plane, the blade portion can be formed by utilizing the original shape of the single crystal diamond. Therefore, it is not necessary to perform complicated processing on the single crystal diamond, and the blade portion can be easily formed, so that the processing cost can be reduced accordingly. That is, in this case, since the (100) crystal plane has already appeared on each face of the hexahedron, only the thread shape of the cutting edge is cut out from the hexahedron, so that the blade portion having the above-described configuration can be obtained. It can be formed easily.

  Further, the rake face is composed of (100) crystal planes, and the ridge lines between adjacent flank faces are positioned on the (100) crystal face, so that wear resistance at the rake face and ridge lines between the flank faces is obtained. As a result, the durability can be improved.

  According to the threading milling machine of the fourth aspect, in addition to the effect achieved by the threading milling machine of the third aspect, the seat surface on which the chip is placed is provided on the tool body, and the seating surface includes an axis and the cutting edge of the cutting blade. Since the structure is inclined with respect to a virtual plane passing through the crest of the thread shape, the chip is composed of a single crystal diamond which is a hexahedron and each surface is composed of a (100) crystal plane, and the rake face is a (100) crystal plane. Even when the ridgeline between adjacent flank faces is positioned on the (100) crystal plane, unnecessary contact between the flank face and the cutting surface of the workpiece can be avoided. is there. In other words, by utilizing the original shape of single crystal diamond, it is possible to form a blade without complicated processing, and the flank contacts the cutting surface while improving the wear resistance at the ridgeline between the flank surfaces. You can avoid that.

  According to the threading milling of the fifth aspect, in addition to the effect of the threading milling of the second aspect, at least a part of the cutting edge is located on the (111) crystal plane of the single crystal diamond. The strength of the cutting edge can be increased by using the (111) crystal face, which is said to have the highest hardness among the crystal faces of crystalline diamond, as the cutting edge. Therefore, it is possible to suppress chipping or wear generated on the cutting edge, and there is an effect that the tool life can be further improved correspondingly.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. FIG. 1 is a front view of a thread cutting mill 1 according to a first embodiment of the present invention, and FIG. 2 is a front view of the thread cutting mill 1 viewed from the direction of arrow II in FIG. The arrow II direction is parallel to the axis O direction.

  First, the overall configuration of the thread cutting mill 1 will be described with reference to FIG. The thread cutting mill 1 is a cutting tool for forming a female screw on the inner peripheral surface of a prepared hole by a rotational force transmitted from a processing machine (not shown) such as an NC milling machine or a machining center, and is shown in FIG. As described above, a tool body 10 made of a cemented carbide obtained by pressure-sintering tungsten carbide (WC) or the like, and a tip of the tool body 10 (lower side in FIG. 1) is made of single crystal diamond. The chip 20 is provided. In addition, the tool main body 10 is not restricted to being comprised from a cemented carbide alloy, For example, you may comprise the tool main body 10 from high speed tool steel.

  The tool body 10 includes a shank 11 provided on the rear end side (upper side in FIG. 1) and a body 12 provided on the front end side (lower side in FIG. 1) connected to the shank 11. ing. The shank 11 is a part held by the processing machine, and is formed in a columnar shape centered on the axis O as shown in FIGS. 1 and 2.

  The thread cutting mill 1 has a tool body 10 held by a processing machine via the shank 11 and is rotated around an axis O by a driving force transmitted from the processing machine and is below a workpiece (not shown). The lead 20 is lead-feeded in the direction of the axis O while revolving in the hole, so that the internal thread of the workpiece is cut by the tip 20 on the inner peripheral surface of the workpiece.

  The shank 11 is not limited to being formed in a columnar shape having a constant outer diameter along the axis O. For example, the outer diameter of the shank 11 increases from the front end side to the rear end side of the tool body 10. You may form in the taper shape which reduces.

  The body 12 is a part to which the blade portion 20 is attached. As shown in FIGS. 1 and 2, the body 12 is formed in a cylindrical shape having a constant outer diameter along the axis O, and one of the cylindrical bodies. A seating surface 13 formed by cutting out a portion is provided. Note that the outer diameter of the body 12 is smaller than the outer diameter of the shank 11.

  The seat surface 13 is a mounting surface for brazing the blade portion 20, and is formed in a planar shape parallel to the axis O, as shown in FIG. 2, and is formed at the tip of the body 12 (lower side in FIG. 1). Is formed.

  The tip 20 is a screw cutting tip that is used for cutting a workpiece, and is configured as a plate-like piece from single crystal diamond, and the blade portion 30 (see FIG. 3) is an outer periphery of the tool body 10 (body 12). It is fixed (brazed) to the seat surface 13 in a state of protruding to the side.

  Thus, according to the thread cutting mill 1 in this Embodiment, since the chip | tip 20 is comprised from the single crystal diamond, the intensity | strength of the blade part 30 can be raised. Therefore, chipping or wear generated on the cutting edge 31 (see FIG. 3) can be suppressed, and the tool life can be improved correspondingly.

  Further, if the wear of the blade part 30 can be suppressed, the change in the shape of the blade part 30 (the cutting edge 31) accompanying the increase in the number of threading processes can be reduced, so that the change in the machining accuracy of the workpiece can be reduced. Thus, the dimensional accuracy of the female screw can be improved. Thus, the reduction in the shape change of the blade portion 30 (the cutting edge 31) is particularly effective in the thread cutting mill 1 in which the shape of the blade portion 30 (the cutting edge 31) is transferred as it is as the internal thread shape of the workpiece. is there.

  Furthermore, according to the thread milling cutter 1 in the present embodiment, since the tip 20 is made of single crystal diamond, the cut surface of the workpiece can be finished more smoothly than the finished surface by polishing. Therefore, since it is formed in the workpiece, the strength of the screw can be improved.

  Next, the detailed configuration of the chip 20 will be described with reference to FIG. 3 (a) is a partially enlarged front view of the threaded milling cutter 1 showing the IIIa portion of FIG. 1 partially enlarged, and FIG. 3 (b) is a partially enlarged view of the IIIb portion of FIG. FIG. 2 is a partially enlarged front end view of the thread cutting mill 1 shown in FIG.

  The tip 20 includes a blade portion 30, and is brazed and fixed to the seating surface 13 with the blade portion 30 protruding to the outer peripheral side (right side in FIG. 3A). The blade portion 30 mainly includes a rake face 31, a flank face 32, and a cutting edge 33 formed on the rake line of the rake face 31 and the flank face 32.

  The rake face 31 is a part for generating and discharging chips when the workpiece is cut by the cutting edge 33. As shown in FIGS. 3 (a) and 3 (b), the outer surface of the blade part 30 is used. In this case, it is constituted by a surface opposite to the one surface brazed to the seating surface 13, and is formed in a planar shape parallel to the seating surface 13.

  The flank 32 is a part for reducing the contact area between the blade portion 30 and the workpiece when the workpiece is cut by the cutting edge 33, and is a plane inclined at a predetermined clearance angle with respect to the rake face 31. It is formed in a shape. In the present embodiment, the flank 32 and the rake face 31 are configured to be orthogonal to each other.

  The cutting edge 33 is a part that directly participates in the cutting of the workpiece. As described above, the cutting edge 33 is formed at the ridge line where the rake face 31 and the flank face 32 intersect, and FIGS. 3 (a) and 3 (b). As shown in (), a thread shape corresponding to the thread groove of the workpiece to be processed is formed. In the present embodiment, as shown in FIG. 3A, the cutting edge 33 is formed in a single thread shape.

  Here, in the present embodiment, the thread shape of the cutting edge 33 is formed by laser irradiation. As a result, the thread shape (cutting edge 33) can be formed in a short time on the single crystal diamond that is difficult to polish, and as a result, the processing cost can be reduced.

  In addition, since the (111) crystal plane of the single crystal diamond cannot be processed in the polishing process, when it is necessary to process the (111) crystal plane when forming the thread shape of the cutting edge 33, It is necessary to perform polishing while adjusting the orientation of the single crystal diamond (adjusting the orientation so that the (111) crystal plane does not need to be processed), which increases the processing cost.

  On the other hand, according to the thread cutting mill 1 in the present embodiment, since it is configured to form the thread shape of the cutting edge 33 by laser irradiation, even when the (111) crystal plane needs to be processed, Such a (111) crystal plane can be melted by a laser to easily form the thread shape of the cutting edge 33. Therefore, there is no need to perform the operation of adjusting the orientation of the single crystal diamond, and the processing cost can be reduced accordingly.

  Further, in the present embodiment, the tip 20 is a hexahedron and each surface is made of single crystal diamond having a (100) crystal face, and the blade portion 30 has a rake face 31 made of a (100) crystal face. And the ridgeline 32a between adjacent flank surfaces 32 is positioned on the (100) crystal plane.

  Thereby, the blade part 30 can be formed utilizing the original shape of the single crystal diamond. Therefore, it is not necessary to perform complicated processing on the single crystal diamond, and the blade portion 30 can be easily formed, so that the processing cost can be reduced accordingly. That is, in this case, since the (100) crystal plane has already appeared on each face of the hexahedron, only the thread shape of the cutting edge 31 is cut out by laser irradiation with respect to the hexahedron (only the flank face 32). The blade portion 30 having the above-described configuration can be easily formed.

  Further, the rake line 31 is constituted by the (100) crystal face and the ridge line 32a between the adjacent flank faces 32 is positioned on the (100) crystal face, thereby the ridge line between the rake face 31 and the flank face 32. The wear resistance in 32a can be improved to improve durability.

  Here, as shown in FIG. 3B, the seat surface 13 is inclined to the rear side in the cutting direction (lower side in FIG. 3B) with respect to the virtual plane P at an inclination angle θ. That is, the seat surface 13 increases the distance from the virtual plane P as it is separated from the axis O (see FIG. 2). The virtual plane P is a virtual plane that includes the axis O and passes through the thread-shaped peak crest t of the cutting edge 33.

  As a result, the tip 20 is a hexahedron and each surface is made of a single crystal diamond having a (100) crystal face, the rake face 31 is made of a (100) crystal face, and the ridge line 32a between adjacent flank faces 32 is formed. Even when it is configured to be positioned on the (100) crystal plane, unnecessary contact between the flank 32 and the cutting surface of the workpiece can be avoided. That is, by utilizing the original shape of the single crystal diamond, the blade portion 30 can be formed without performing complicated processing, and the flank 32 is cut while improving the wear resistance at the ridge line 32a between the flank 32. Contact with the surface can be avoided.

  Next, a method for manufacturing the thread cutting mill 1 will be described. When manufacturing the thread milling cutter 1, first, the shank 11 and the body 12 are processed into a blank (not shown) made of a cemented carbide to form the tool body 10, and the body 12 of the tool body 10 is cut. The seat surface 13 is formed by cutting (tool body forming step).

  After the seating surface 13 is formed, one surface of the single crystal diamond, each surface comprising (100) crystal faces, is brazed to the seating surface 13 to fix the single crystal diamond to the seating surface 13 (fixing step). Next, the cutting edge 33 is formed by irradiating the fixed single crystal diamond with a laser (cutting edge forming step).

  In the cutting edge forming step, a laser beam (laser type: yag laser, pulse output: 4 mJ, pulse width: 3 ms, pulse frequency: 50 kHz) is applied to the single crystal diamond (chip 20) by a laser processing machine (not shown). Irradiation forms the thread shape shown in FIG. 3 (a) (the flank 32 is formed). Thereby, the cutting edge 33 is formed in the ridgeline part where the rake face 31 and the flank 32 intersect.

  Next, test results of an endurance test performed using the conventional thread milling cutter and the thread cutting mill 1 according to the present embodiment will be described. The durability test compares the durability between the thread cutting milling machine and the thread cutting milling machine 1 according to the present embodiment. The number of machining operations that can cut the internal thread within a predetermined dimensional accuracy on the inner surface of the prepared hole in the workpiece. Measured and compared.

  Detailed specifications of the endurance test are as follows: Workpiece material: ADC12, projecting dimension of the tip 20 from the outer periphery of the body 12: 4.5 mm, processing screw size: M6 × 1, pilot hole diameter: φ5.1 mm, pilot hole Length x screw length: 15 mm x 9 mm, peripheral speed: 300 m / min, feed per tooth (feed per rotation): 0.1 mm / t, processing machine: vertical machining center, cutting oil: water-soluble cutting It is an oil agent (diluted 10 times).

  In addition, the conventional threading mill is comprised in the same shape (dimension) except the point from which the material of the chip | tip 20 is comprised from a cemented carbide with respect to the threading mill 1 in this Embodiment. Further, in the durability test, the state of the tip (blade part) was confirmed every time 1,000 holes were processed, and it was determined whether or not the wear amount reached a predetermined amount.

  As a result of the durability test, in the conventional thread cutting mill, the wear of the tip (blade) has reached a predetermined amount at the time of 20,000 holes, and the subsequent processing becomes impossible. In the thread milling machine 1 in FIG. 1, even when 50,000 holes are machined, the wear amount of the tip 20 (blade part 30) does not reach a predetermined amount, and no damage is found in the blade part 30, and further machining is possible. It was a state.

  Next, with reference to FIG. 4, a thread cutting mill 201 according to the second embodiment will be described. In addition, about the structure same as 1st Embodiment, the same code | symbol is attached | subjected and the description is abbreviate | omitted.

  FIG. 4A is a partially enlarged front view of the thread cutting mill 201 according to the second embodiment, and corresponds to FIG. FIG. 4B is a partially enlarged front end view of the thread milling mill 201 and corresponds to FIG.

  As in the first embodiment, the tip 220 in the second embodiment is brazed and fixed to the seating surface 13 with the blade portion 230 protruding to the outer peripheral side (right side in FIG. 4A). The blade portion 230 mainly includes a rake face 231, a flank face 232, and a cutting edge 233 formed on the ridge line of the rake face 231 and the flank face 232.

  The cutting edge 33 is formed in a thread shape corresponding to the thread groove of the workpiece to be processed. In the present embodiment, as shown in FIG. It is formed in a mountain shape. Since the three thread shapes have the same configuration, in FIG. 4 (a), only one thread is denoted by the reference numeral in order to simplify the drawing and facilitate understanding. The symbols for the two peaks are omitted.

  Here, in the thread milling cutter 201 in the second embodiment, as in the case of the first embodiment, the chip 220 is made of single crystal diamond that is a hexahedron and each surface has a (100) crystal plane, The blade portion 230 is configured such that the rake face 231 is constituted by a (100) crystal face and the ridge line 232a between adjacent flank faces 232 is located on the (100) crystal face.

  The present invention has been described above based on the embodiments. However, the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It can be easily guessed.

  In the above-described embodiment, the case where the chips 20 and 220 are made of single crystal diamond which is a hexahedron and each surface (outer surface) is a (100) crystal face has been described, but the present invention is not necessarily limited thereto. Of course, it is possible to construct the chips 20 and 220 with other crystal planes as outer surfaces.

  Although not described in the above embodiment, the chips 20 and 220 may be made of artificial single crystal diamond or may be made of natural single crystal diamond. However, when the chips 20 and 220 are composed of hexahedral single crystal diamonds in which each surface (outer surface) is a (100) crystal plane, it is preferably composed of artificial single crystal diamond. This is a case where only a simple process (formation of the thread shape of the cutting edges 33 and 233) is performed by forming the blade portion from an artificial single crystal diamond with less distortion in shape compared to natural single crystal diamond. However, it is because the blade parts 30 and 230 can be configured with high accuracy.

  In the above-described embodiment, the case where the cutting edges 33 and 233 are formed in one or three threads is described, but the present invention is not necessarily limited thereto. For example, it may have two thread shapes, or may have four or more thread shapes.

  In the above embodiment, the case where the cutting edges 33 and 233 are located on the (100) crystal plane has been described. However, the present invention is not necessarily limited to this, and may be located on another crystal plane. For example, you may comprise so that at least one part of a cutting edge may be located on a (111) crystal plane. In this case, the strength of the cutting edge can be increased by using the (111) crystal face, which is said to have the highest hardness among the crystal faces of the single crystal diamond, as the cutting edge. Therefore, chipping or wear generated on the cutting edge can be suppressed, and the tool life can be further improved correspondingly.

It is a front view of the thread cutting mill in 1st Embodiment of this invention. FIG. 2 is a front end view of the thread cutting mill as viewed from the direction of arrow II in FIG. 1. (A) is the partial expansion front view of the thread cutting milling partially shown IIIa part of Drawing 1, and (b) is the threading milling cutter which expanded and showed part IIIb part of Drawing 2 FIG. (A) is a partial expanded front view of the thread cutting mill in 2nd Embodiment, (b) is the partial expanded front view of a thread cutting mill.

Explanation of symbols

1,201 Thread milling machine O Oxis 10 Tool body 11 Shank (Part of tool body)
12 Body (part of tool body)
13 Seat 20 Tip 30 Blade 31 Rake face (part of blade)
32 Flank (part of blade)
32a, 232a Ridge line 33 between flank surfaces Cutting edge (part of blade)
t Thread-shaped summit P Virtual plane

Claims (5)

Thread shape corresponding to the thread groove to be machined, the tool body having a tool body rotated about an axis and a tip attached to the tool body with the blade part protruding to the outer peripheral side Thread cutting for cutting a female thread into a pilot hole of the workpiece by the blade portion of the tip by rotating the tool body relative to the workpiece while rotating about the axis. In milling
A thread milling cutter, wherein the tip is made of single crystal diamond.   The thread cutting mill according to claim 1, wherein the thread shape of the cutting edge is formed by laser irradiation. The chip is composed of single crystal diamond that is hexahedral and each surface is composed of (100) crystal planes,
In the blade portion, the ridge line of the rake face and the flank face is the cutting edge, the rake face is constituted by a (100) crystal face, and the ridge line between adjacent flank faces is located on the (100) crystal face. The threaded milling cutter according to claim 2, wherein:   The tool body includes a seating surface on which the chip is placed, and the seating surface is inclined with respect to a virtual plane that includes an axis and passes through the top of the thread shape of the cutting edge. The threaded milling cutter according to claim 3.   The thread cutting miller according to claim 2, wherein the edge portion of the rake face and the flank face is a cutting edge, and at least a part of the cutting edge is located on a (111) crystal plane.

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