JP2017087373A - Rotary Cutting Tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary cutting tool that can reduce surface roughness in the vicinity of an inlet of a processing hole.SOLUTION: A rotary cutting tool 1 comprises a base metal 10 and a plurality of chips 30 and 130 arranged around an outer periphery of the base metal 10. The plurality of chips 30 and 130 are arranged on the same rotation track, and each of the plurality of chips 30 and 130 has outer peripheral cutting blades 31 and 131. At least one of the plurality of outer peripheral cutting blades 31 and 131 protrudes toward an outer periphery side with respect to the other cutting blade.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a rotary cutting tool. More specifically, the present invention relates to a rotary cutting tool in which a plurality of chips are provided on the outer periphery of a base metal.

  Commonly used rotary cutting tools such as reamers are (1) rotary cutting tools having a hard sintered body (polycrystalline diamond, etc.) cutting edge with a margin around the cutting edge, (2 ) A rotary cutting tool with a single-crystal diamond cutting edge, with a sharp cutting edge with no margin on the outer periphery of the cutting edge, with a guide pad at a position retracted in the tool axis direction with respect to the cutting edge Cutting tools, etc.

  In the case of (1) above, there is an effect of suppressing tool chatter by a margin (guide effect), but there is also an effect of rubbing and pressing the processing surface (vanishing effect), so that burrs are likely to occur on the exit side of the processing hole, There is a problem that springback and burning tend to occur.

  In the case of (2) above, the sharp outer peripheral cutting edge of single crystal diamond suppresses burrs and springback / burning generated on the exit side of the machining hole, but it is retracted in the tool axis direction with respect to the cutting edge. Because of the position of the guide pad, tool chatter is likely to occur when the tool begins to enter the hole (when the single crystal diamond cutting edge starts to act on the machined surface and the guide pad is not yet in contact with the machined surface). There's a problem. In particular, this phenomenon can occur remarkably in a single-blade reamer or the like. In this case, the surface roughness near the entrance of the machining hole is increased. Similar problems occur with rotary cutting tools other than reamers, such as drills.

  Conventional rotary cutting tools are disclosed in the following documents.

Japanese Utility Model Publication No. 7-15227 JP 2008-194779 A JP-A-8-39350 JP 2002-200518 A

  Accordingly, the present invention has been made to solve the above-described problems, and an object of the present invention is to provide a rotary cutting tool capable of reducing the surface roughness in the vicinity of the entrance of the machining hole.

  A rotary cutting tool according to an aspect of the present invention includes a base metal and a plurality of chips provided on the outer periphery of the base metal, the plurality of chips are provided on the same rotation track, and each of the plurality of chips is cut. The blade has a blade, and at least one of the plurality of cutting blades protrudes to the outer peripheral side from the other cutting blades.

  According to this invention, it is possible to reduce the surface roughness in the vicinity of the entrance to the machining hole.

FIG. 3 is a plan view of the rotary cutting tool according to the first embodiment. It is a top view which expands and shows the front-end | tip part of the rotary cutting tool of FIG. It is the side view seen from the direction shown by arrow III in FIG. 6 is a side view showing a margin of the rotary cutting tool according to the first embodiment. FIG. It is a top view which shows the counterbore part provided in the base metal. It is the side view seen from the direction shown by arrow VI in FIG. It is a top view which shows the counterbore part provided in the base metal. It is the side view seen from the direction shown by arrow VIII in FIG. 6 is a plan view of a rotary cutting tool according to Embodiment 2. FIG. It is a top view which expands and shows the front-end | tip part of the rotary cutting tool of FIG. It is sectional drawing along the XI-XI line in FIG. It is the side view seen from the direction shown by arrow XII in FIG.

[Description of Embodiment of the Present Invention]
First, embodiments of the present invention will be listed and described.

  A rotary cutting tool according to an aspect of the present invention includes a base metal and a plurality of chips provided on the outer periphery of the base metal, the plurality of chips are provided on the same rotation track, and each of the plurality of chips is cut. The blade has a blade, and at least one of the plurality of cutting blades protrudes to the outer peripheral side from the other cutting blades.

  In the rotary cutting tool configured as described above, the plurality of chips are provided on the same rotation track, and each of the plurality of chips has a cutting edge. Therefore, when the rotary cutting tool starts to enter the hole, the plurality of cutting edges can contact the hole, so that chattering can be suppressed. Furthermore, at least one of the plurality of cutting edges protrudes toward the outer peripheral side from the other cutting edges. As a result, when the protruding cutting edge processes the workpiece, the occurrence of burrs, springbacks, burns, and the like can be suppressed on the exit side of the processing hole.

  Preferably, no margin is provided in the chip provided with the cutting edge protruding on the outer peripheral side, or a margin having a width of less than 0.02 mm is provided. In this case, since the margin is not provided or is extremely small even if provided, the sharpness of the protruding chip can be improved.

  Preferably, the plurality of chips includes two or more chips, and the margin width of the chip provided with the cutting edge protruding to the outer peripheral side is smaller than the margin width of the other chips. In this case, since the margin of the chip protruding to the outer peripheral side is small, cutting can be performed mainly with the chip protruding to the outer peripheral side.

  Preferably, the length of the cutting edge protruding toward the outer peripheral side in the rotation axis direction is shorter than the length of the other cutting edges in the rotation axis direction. In this case, since the length of the cutting edge protruding to the outer periphery is short, cutting resistance can be reduced. The cutting edge that does not protrude to the outer peripheral side acts as a guide pad. Since the length of the cutting edge is long, it works sufficiently as a guide pad. As a result, chatter can be suppressed.

Preferably, the plurality of tips includes diamond.
Preferably, the tip provided with a cutting edge protruding on the outer peripheral side includes single crystal diamond, and the other tip includes diamond, CBN, or hard ceramic.

[Details of the embodiment of the present invention]
(Embodiment 1)
FIG. 1 is a plan view of a rotary cutting tool according to the first embodiment. FIG. 2 is an enlarged plan view showing a tip portion of the rotary cutting tool of FIG. Referring to FIGS. 1 and 2, rotary cutting tool 1 according to the first embodiment is a reamer. The rotary cutting tool 1 has a base metal 10.

  The base metal 10 extends in the longitudinal direction. Chips 30 and 130 are provided at the tip of the base metal 10. The base metal 10 is provided with a groove 11 extending in the longitudinal direction. Chips 30 and 130 are disposed in the groove 11.

  The base metal 10 is made of, for example, a cemented carbide. The chips 30 and 130 are fixed to the base metal 10 by brazing. In this embodiment, the chips 30 and 130 are directly fixed to the base metal 10, but the chips 30 and 130 may be fixed to the base by brazing and the base may be fixed to the base 10 by bolts.

  The chip 30 is composed of, for example, single crystal diamond formed by chemical vapor deposition (CVD) and a cemented carbide base that holds the single crystal diamond. The chip 130 is made of, for example, diamond, CBN, or hard ceramic.

  The plurality of chips 30 and 130 are provided on the same circumferential track. However, the rotation diameter D1 of the outer periphery of the chip 30 is larger than the rotation diameter D2 of the outer periphery of the chip 130. Therefore, the chip 130 has a function as a guide pad. The chip 130 contacts the processing surface and crushes the nest (cavity) of the processing surface. The three chips 130 are provided at an equal distance from the rotation axis 5 as the rotation center. The difference between the diameters D1 and D2 is preferably 1 μm or more and 10 μm or less.

  The chip 30 includes an outer peripheral cutting edge 31 and front cutting edges 32 and 34 connected to the outer peripheral cutting edge 31. A cutting edge corner 33 is formed between the outer peripheral cutting edge 31 and the front cutting edge 34. A portion surrounded by the outer peripheral cutting edge 31 and the front cutting edges 32 and 34 is a rake face 35.

  The front cutting edge 34 has an inclination angle θ1. The inclination angle θ1 is an angle formed by the front cutting edge 34 with respect to the radial direction. The inclination angle θ1 may not be provided.

  The chip 30 includes single crystal diamond synthesized by CVD or single crystal diamond by direct synthesis using high temperature and high pressure conditions. The chip 130 is made of diamond, CBN, or hard ceramic. Note that the chip 30 and the chip 130 may be made of the same material.

  The chip 130 includes an outer peripheral cutting edge 131 and front cutting edges 132 and 134 connected to the outer peripheral cutting edge 131. A cutting edge corner portion 133 is formed between the outer peripheral cutting edge 131 and the front cutting edge 134. The front cutting edge 134 has an inclination angle θ1. The inclination angle θ1 is an angle formed by the front cutting edge 134 with respect to the radial direction. The inclination angle θ1 may not be provided.

  The length of the chip 30 is shorter than the length of the chip 130. By making the tip 130 longer, the contact area between the tip 130 serving as a guide pad and the hole surface of the workpiece can be increased, thereby suppressing chattering. By reducing the length of the tip 30, the cutting resistance at the tip 30 can be reduced.

  FIG. 3 is a side view seen from the direction indicated by arrow III in FIG. The four chips 30 and 130 are arranged at an angle of 90 ° with respect to the rotation direction. In this embodiment, the chips 30 and 130 are arranged at equal intervals.

  However, the chips 30 and 130 may not be arranged uniformly, and the chips 30 and 130 may be arranged unevenly. In this embodiment, the number of chips 130 is three, but more or fewer chips 130 may be provided. One or more chips 130 may be provided.

  A main hole 22, a branch hole 23 and an opening 21 for supplying cutting fluid to the chips 30 and 130 are provided. The cutting fluid supplied from the main hole 22 is supplied to the chips 30 and 130 via the branch hole 23 and the opening 21.

  FIG. 4 is a side view showing a margin of the rotary cutting tool according to the first embodiment. Referring to FIG. 4, the tip 30 is provided with a clearance angle θ2. An angle formed by the flank 37 with respect to the rotation direction is a flank angle θ2.

  A margin 39 having a width W1 is provided at the outer peripheral end of the chip 30. The margin 39 is provided behind the cutting edge corner 33 in the rotational direction indicated by the arrow 2. The margin 39 may not be provided. When the margin 39 is provided, the width W1 is less than 0.02 mm. The chip 130 is provided with a margin (not shown) wider than the margin 39.

  FIG. 5 is a plan view showing a counterbore provided on the base metal. FIG. 6 is a side view seen from the direction indicated by the arrow VI in FIG. With reference to FIGS. 5 and 6, the base metal 10 is provided with a counterbore portion 15. The counterbore part 15 is a recessed part. The chip 30 is fitted to the counterbore part 15.

  FIG. 7 is a plan view showing a counterbore portion provided on the base metal. FIG. 8 is a side view seen from the direction indicated by the arrow VIII in FIG. With reference to FIGS. 7 and 8, the base metal 10 is provided with a counterbore portion 16. The counterbore 16 is a recess. The chip 130 is fitted to the counterbore part 16. FIG. 8 shows a base metal obtained by rotating the base metal of FIG. 6 by 90 ° about the rotation shaft 5 in the clockwise direction.

The operation and effect of the rotary cutting tool 1 configured as described above will be described.
(1) About burr suppression at the machining hole exit side With the conventional rotary cutting tool, a “negative plastic zone” is created in the part where the cutting edge is going to cut (the part that becomes the chip), and the exit side end face of the machining hole is formed. As the cutting edge approaches, plastic deformation occurs at that part, and burrs are generated.

  To suppress burrs, the negative plastic area is reduced. For this purpose, it is necessary to lower the cutting resistance, further improve the sharpness of the tool and maintain the sharpness.

  In the rotary cutting tool 1, since at least one cutting edge is a sharp cutting edge with no margin or minimal margin, burrs can be suppressed.

  Moreover, by using single-crystal diamond as the cutting edge, the cutting edge can be further sharpened, the sharpness can be improved, and the cutting resistance can be lowered. Furthermore, the wear resistance of the cutting edge can be improved.

(2) About spring back (machining diameter shrinkage) and suppression of burning In conventional rotary cutting tools, friction heat and torque are generated by the margin pressing and rubbing the machined surface. The frictional heat causes burning, which causes elasto-plastic deformation due to processing load and torque, causing springback.

  In the rotary cutting tool 1, since the margin is eliminated or a sharp cutting edge with a minimum margin is used, the frictional heat and torque can be reduced. Moreover, since the cutting edge is made of single crystal diamond, it is more excellent in sharpness, which is advantageous over other tool materials in reducing frictional heat and torque.

  In addition, since the thermal conductivity of single crystal diamond is much higher than that of cemented carbide and polycrystalline diamond, cutting heat is reduced and the effect of preventing burning is increased.

(3) Reasons for combining a cutting edge with no margin and a cutting edge with a margin Providing a margin has the adverse effect of causing springback and burning, but has the effect of suppressing tool chatter (guide effect). .

  In the rotary cutting tool 1, the plurality of tips 30, 130 are provided on the same circumference at the tip of the base metal 10, so that the plurality of outer peripheral cutting edges 31, 131 simultaneously contact the workpiece at the start of machining. Moreover, since there is one or more cutting edges provided with a margin, the margin serves as a guide, and tool chatter can be suppressed from the start of machining. Moreover, at least one of the cutting edges has no margin or has a minimal margin, and the processing surface rubbed with the margin can be removed by projecting to the outer periphery of the cutting radius with respect to the tool radial direction. And the quality of the machined surface can be improved.

(Embodiment 2)
FIG. 9 is a plan view of the rotary cutting tool according to the second embodiment. FIG. 10 is an enlarged plan view showing a tip portion of the rotary cutting tool of FIG. 9 and 10, the rotary cutting tool 1 according to the second embodiment is thinner than the rotary cutting tool 1 according to the first embodiment, and the ratio of the grooves 11 to the entire length of the tool is large. Furthermore, it differs from the rotary cutting tool 1 according to Embodiment 1 in that the entire front cutting edges 32 and 132 form an angle θ1 with respect to the radial direction.

  11 is a cross-sectional view taken along line XI-XI in FIG. FIG. 12 is a side view seen from the direction indicated by arrow XII in FIG. This embodiment differs from the rotary cutting tool 1 according to the first embodiment in which such margins are not provided in that the base 10 is provided with margins having widths W3 and W4.

(Example)
Sample 1 (invented reamer) of the rotary cutting tool 1 according to the first embodiment, sample 2 (four-blade PCD reamer) in which the tip 30 of the first embodiment is replaced with a polycrystalline diamond tip, Sample 3 (one-blade PCD reamer) from which only one chip 130 of Embodiment 1 is left and other chips 30 and 130 are removed, and only one chip 30 of Embodiment 1 is left, and other chips 130 are left. Sample 4 (single-edged CVD reamer) from which was removed was prepared. The dimensions are shown below.

Sample 1 (Invention)
L1 = 2.3 mm, L2 = 6 mm, θ1 = 15 ° of chips 30 and 130, θ2 = 12 ° of chip 30, θ2 = 15 ° of chip 130, margin W1 of chip 30 = 1 μm, margin W1 of chip 130 0.2mm
Sample 2 (4-flute PCD)
L2 = 6 mm, θ1 = 15 ° of chip 130, θ2 = 15 ° of chip 130, margin W1 of chip 130 = 0.2 mm
Sample 3 (single blade PCD)
L2 = 6 mm, θ1 = 15 ° of chip 130, θ2 = 15 ° of chip 130, margin W1 of chip 130 = 0.2 mm
Sample 4 (single blade CVD)
L1 = 2.3 mm, θ1 = 15 ° of chip 30, θ2 = 12 ° of chip 30, margin W1 of chip 30 = 1 μm
A vertical machining center (spindle BT30) was used as a processing apparatus. The coolant was a water-soluble emulsion (diluted 10%), and the composition of the work material was ADC12. A prepared hole having a diameter of 13.5 mm and a depth of 35 mm was formed in the work material. This prepared hole was processed with a rotary cutting tool 1 as a reamer.

  The processing conditions were a cutting speed: 150 m / min, a feed amount: 0.2 mm / rev, and a machining allowance of 0.25 mm on one side.

  The sample 1-4 was processed under the above conditions, and the surface roughness at the mouth (inlet) and the back of the hole was measured. The results are shown below.

Sample 1 (Invention)
The surface roughness Ra of the hole mouth was 0.12 μm, and the surface roughness Ra of the hole depth was 0.14 μm.

Sample 2 (4-flute PCD)
The surface roughness Ra of the hole mouth was 0.17 μm, and the surface roughness Ra of the hole depth was 0.16 μm.

Sample 3 (single blade PCD)
The surface roughness Ra of the hole mouth was 0.2 μm, and the surface roughness Ra of the hole depth was 0.19 μm.

Sample 4 (single blade CVD)
The surface roughness Ra of the hole mouth was 0.23 μm, and the surface roughness Ra of the hole depth was 0.15 μm.

  The embodiments and examples disclosed herein are illustrative in all respects and should not be construed as being restrictive. The scope of the present invention is shown not by the above-described embodiment but by the scope of claims, and is intended to include meanings equivalent to the scope of claims and all modifications within the scope.

  The present invention can be used in the field of rotary cutting tools.

  1 rotary cutting tool, 2 arrows, 5 rotary shaft, 10 base metal, 11 groove, 15, 16 counterbore part, 21 opening, 22 main hole, 23 branch hole, 30, 130 chip, 31, 131 outer peripheral cutting edge, 32, 34, 132, 134 Front cutting edge, 33, 133 Corner edge, 35 Rake face, 37 Flank, 39 Margin.

Claims (6)

Comprising a base metal and a plurality of chips provided on the outer periphery of the base metal;
The plurality of chips are provided on the same rotation path,
Each of the plurality of chips has a cutting edge,
At least one of the plurality of cutting edges is a rotary cutting tool that protrudes to the outer peripheral side from the other cutting edges.   2. The rotary cutting tool according to claim 1, wherein no margin is provided on the chip provided with the cutting edge protruding on the outer peripheral side, or a margin having a width of less than 0.02 mm is provided.   3. The chip according to claim 1, wherein the plurality of chips includes two or more chips, and a margin width of the chip provided with a cutting edge protruding to the outer peripheral side is smaller than a margin width of the other chips. The described rotary cutting tool.   The rotary cutting tool according to any one of claims 1 to 3, wherein a length of the cutting edge protruding toward the outer peripheral side in a rotation axis direction is shorter than a length of another cutting edge in a rotation axis direction.   The rotary cutting tool according to claim 1, wherein the plurality of tips include diamond.   The rotary cutting tool according to claim 5, wherein the tip provided with a cutting edge protruding on the outer peripheral side includes single crystal diamond, and the other tip includes diamond, CBN, or hard ceramics.