Cutting tool

Abstract

To provide a cutting tool which easily forms a hole finished with an inner peripheral surface in a material to be cut.SOLUTION: A cutting tool 1 comprises: a shank 10 extending along a rotation axis O1; and a body 15 provided at a tip side of the shank 10. The body 15 includes: a lead part 16 whose base end is continuous with the shank 10; and a drill part of a tip side of the lead part. In the lead part 16, a cross-sectional shape orthogonal to the rotation axis O1 has a shape including: a plurality of projections 20 respectively projecting radially at equal intervals from the rotation axis O1; and hollow parts 21 that concavely join neighboring projections 20 to each other.SELECTED DRAWING: Figure 1

Description

[Technical field]

[0001] The present invention relates to a cutting tool. [Background technology]

[0002] 2. Description of the Related Art Conventionally, cutting tools such as drills and reamers have been used to machine workpieces such as carbon steel and alloy steel (see, for example, Patent Document 1). To form a hole in a workpiece, a drill is first attached to a machine tool such as a machining center. A pilot hole with an inner diameter smaller than the target hole is formed in the workpiece using this drill. The drill is then removed from the machine tool, and a reamer is attached to the machine tool. The reamer is used to enlarge the pilot hole in the workpiece and finish the inner peripheral surface of the hole. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Patent No. 5940208 Summary of the Invention [Problem to be solved by the invention]

[0004] However, in order to form holes in a workpiece with high accuracy while changing the cutting tool attached to the machine tool, a great deal of effort is required, including the need to chuck the cutting tool to the machine tool with high accuracy.

[0005] The present invention has been made in consideration of the above problems, and has an object to provide a cutting tool that can easily form a hole with a finished inner surface in a workpiece. [Means for solving the problem]

[0006] In order to solve the above problems, the present invention can take the following forms. (1) A first aspect of the present invention is a drill having a shank extending along a rotation axis and a body provided on a tip side of the shank, the body having a reamer portion whose base end is connected to the shank and a drill portion on the tip side of the reamer portion, The reamer portion is a cutting tool whose cross-sectional shape perpendicular to the rotation axis has a plurality of protrusions each protruding radially from the rotation axis, and a recessed portion connecting adjacent protrusions in a concave or linear manner.

[0007] (2) Aspect 2 is the cutting tool according to aspect 1, in which the relationship among a diameter D of a circumscribing circle connecting the multiple protrusions, a diameter d of an inscribing circle connecting the bottoms of the multiple depressions, and a distance ΔC1 between the bottoms and the circumscribing circle, which are defined in the shape of the cross section, satisfies the following condition. ΔC1=(Dd) / 2 (3) A third aspect is the cutting tool according to the second aspect, further characterized in that the relationship between a line connecting adjacent protrusions and the circumscribing circle and a distance ΔC2 satisfies the following condition: ΔC1 ≧ ΔC2 0≦(Dd) / (2×△C2)≦1.5

[0008] (4) Aspect 4 is the cutting tool according to aspect 1, wherein the tip of the drill portion has any one of a non-flat drill shape, a flat drill shape, a square end mill shape, a radius end mill shape, and a ball end mill shape. (5) Aspect 5 is a cutting tool as described in aspect 4, wherein the reamer portion has a plurality of chip ejection grooves that are twisted in a first direction along the rotation axis, and the drill portion has a plurality of tip grooves that are twisted in a second direction opposite to the first direction at a predetermined angle relative to the rotation axis.

[0009] (6) Aspect 6 is a cutting tool according to any one of aspects 1 to 5, wherein at least one of the reamer portion and the drill portion is formed of cemented carbide, cubic boron nitride, or polycrystalline diamond sintered body.

[0010] (7) A seventh aspect is a cutting tool according to any one of the first to fifth aspects, wherein at least one of the reamer portion and the drill portion is formed of a cemented carbide having a diamond coating applied to the surface thereof. Effect of the Invention

[0011] The cutting tool of the present invention can easily form a hole having a finished inner surface in a workpiece. [Brief description of the drawings]

[0012] [Figure 1] FIG. 2 is a side view of a cutting tool according to an embodiment of the present invention. [Diagram 2] FIG. [Diagram 3] 2 is a cross-sectional view taken along line A1-A1 in FIG. [Figure 4] FIG. 11 is a side view of a main portion of a cutting tool according to a modified example of an embodiment of the present invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0013] Hereinafter, one embodiment of a cutting tool according to the present invention will be described with reference to Fig. 1 to Fig. 4. Fig. 1 is a side view of a cutting tool 1 according to this embodiment. Fig. 2 is a front view of the cutting tool 1. Fig. 3 is a cross-sectional view taken along the cutting line A1-A1 shown in Fig. 1. The cutting tool 1 includes a shank 10 that is attached to a machine tool (not shown), and a body 15 that functions as a drill reamer. The shank 10 and the body 15 are formed, for example, by cutting out a cylindrical member made of cemented carbide. It is preferable that at least a part of the cemented carbide surface of the body 15 is coated with a diamond film. The central axes (axis lines) of the shank 10 and the body 15 are a common rotation axis O1, and the shank 10 and the body 15 each extend along the rotation axis O1.

[0014] In this specification, the side of the body 15 seen from the shank 10 is referred to as the tip side, and the side of the shank 10 seen from the body 15 is referred to as the base side. Also, the direction along the rotation axis O1 is sometimes referred to as the thrust direction, the direction perpendicular to the rotation axis O1 as the radial direction, and the direction going around the rotation axis O1 as the circumferential direction. Also, the counterclockwise direction when looking at the cutting tool 1 from the base side to the tip side is referred to as the first direction D1, and the clockwise direction is referred to as the second direction D2. The cutting tool 1 is used by rotating in the second direction D2 during cutting.

[0015] The shank end (neck portion of body 15) 11, which connects shank 10 to body 15, is tapered so that the outer diameter gradually decreases toward the tip. Body 15 has a lead portion 16, a cutting edge portion 17, and a blade portion 18. Lead portion 16 and cutting edge portion 17 form a reamer portion, and cutting edge portion 17 and blade portion 18 form a drill portion.

[0016] The lead portion 16 is a base end portion of the body 15, and the shape of a cross section perpendicular to the rotation axis O1, i.e., the cross-sectional shape T1 shown in the figure, has a plurality of (five in this example) protrusions 20 that protrude radially at equal intervals from the rotation axis O1, and a plurality of recesses 21 that connect adjacent protrusions in a concave shape. In the example of FIG. 3, each protrusion 20 has a cross-sectional shape like a bastion of a building, but it may have a cross-sectional shape of a corner of a rounded polygon (including a rounded regular polygon or an unequally divided rounded polygon) or other shapes as long as it functions as a reamer. In addition, the number of protrusions 20 is not limited to five, and may be two or more. By increasing the number of protrusions 20, the rigidity can be increased. If the number of protrusions 20 is three and the shape is a substantially equilateral triangle, the force applied from the workpiece to the lead portion 16 during cutting can be evenly distributed, and cost performance can be improved. The lead portion 16 is formed so that the rotation locus around the rotation axis O1 forms a cylindrical surface centered on the rotation axis O1.

[0017] The relationship between the diameter D [mm] of the circumscribing circle C1 connecting each protrusion 20, the diameter d [mm] of the inscribing circle C2 connecting the bottoms (the parts closest to the rotation axis O1) of each recess 21, the distance ΔC1 [mm] between the bottoms of the recesses 21 and the circumscribing circle C1, and the distance ΔC2 [mm] between the straight line 21a connecting adjacent protrusions 20 and the circumscribing circle C1, as defined in the cross-sectional shape T1 illustrated in FIG. 3, satisfies the following condition. ΔC1=(Dd) / 2 Furthermore, it has been verified that satisfying the following conditions is preferable in terms of work efficiency during cutting. ΔC1 ≧ ΔC2 0≦(Dd) / (2×△C2)≦1.5 By satisfying the above conditions, adhesion of chips from the workpiece is suppressed, and the cutting performance of the workpiece can be improved at the cutting edge portion 17, the blade portion 18, and the protruding portion 20. Furthermore, the roughness of the finished surface can be improved, and the rigidity of the cutting tool 1 can be maintained.

[0018] Each of the protrusions 20 and each of the recesses 21 is twisted spirally in the second direction D2 toward the base end side, that is, left twisted. 3, each recess 21 is curved so as to be convex toward the rotation axis O1 and concave toward the outer periphery D. Also, the concave portion 21 may be the same as the straight line 21a connecting the protrusions 20 to each other.

[0019] When the body 15 is formed by cutting out a cylindrical member indicated by the two-dot chain line L1 in FIG. 3, each protrusion 20 becomes a margin (edge, land (part that remains unmachined)) of the outer circumferential surface of the cylindrical member. Therefore, no further machining process is required for the body 15, particularly the protrusions 20. Also, in this case, the diameter of the cylindrical member is equal to the diameter D of the circumscribed circle C1 in the above-mentioned cross-sectional shape T1. As a result, multiple discharge spaces (chip discharge grooves) S1 for discharging chips of the workpiece (five in the illustrated example) are formed on the radially inner side of the outer circumferential surface of the cylindrical member and on the radially outer side of the recessed portion 21.

[0020] Next, the cutting blade portion 17 and the blade portion 18 that function as the drill portion will be described. As shown in FIG. 1, the cutting blade portion 17 is provided on the tip side of the body 15, closer to the tip side than the lead portion 16. As shown in FIG. 2, the cutting blade portion 17 has two blade portions 18 formed symmetrically with respect to the rotation axis O1. In addition, the tip of the cutting blade portion 17 and the tips of the two blade portions 18 converge on the rotation axis O1, and have a shape having a tip angle θ1 with the rotation axis O1 as the central axis. The tip angle θ1 is 118° in this example, but may be other angles, such as 90° or 140°, depending on the application. The number of the blade portions 18 may be one, or three or more. In this example, each blade portion 18 is a "right blade".

[0021] A tip groove 17a is formed at adjacent positions on the first direction D1 side on the opposite side in the second direction D2 around the rotation axis O1 of the two blade portions 18. As shown in Fig. 1, each tip groove 17a is twisted in a spiral shape (right twist) in the first direction D1 as it approaches the base end side.

[0022] That is, the twist direction of each tip groove 17a is opposite to that of the protrusions 20 and the recesses 21. Therefore, for example, when coolant is injected during wet machining, the coolant flows in the circumferential direction of the protrusions 20 and the recesses 21, while the coolant is concentrated in the direction of the part to be cut. This allows for efficient chip removal and cooling. Each tip groove 17a is connected to a recess 21 of the lead portion 16. In this example, the two tip grooves 17a are formed in the range in which the cutting edge portion 17 is provided in the direction along the rotation axis O1. Therefore, the number of tip grooves 17a is two (i.e., two lines), but the number and the position of formation of the tip grooves 17a are arbitrary as long as the above-mentioned action is achieved.

[0023] Next, a usage example of the cutting tool 1 configured as above will be described. During cutting, the cutting tool 1 is used with the shank 10 attached to a machine tool (not shown). Next, the cutting tool 1 is moved toward the tip side with respect to the workpiece W1 shown in FIG. 1 by the machine tool. When the cutting tool 1 is moved toward the tip side, pilot holes are formed in the workpiece W1 by the multiple cutting portions 18. At this time, chips generated by cutting the workpiece W1 are discharged toward the base end side through each tip groove 17a and multiple discharge spaces S1 (radially outside the recessed portion 21). In this process, the cutting edge portion 17 and the cutting portion 18 of the cutting tool 1 function as a drill.

[0024] Thereafter, the pilot hole is expanded and the inner peripheral surface of the hole is finished by the cutting blade portion 17 and the protruding portion 20. At this time, since the multiple protruding portions 20 are twisted to the left, each protruding portion 20 performs finishing while compressing the inner peripheral surface of the hole. Chips generated when the inner peripheral surface of the hole is finished are discharged toward the base end side through the discharge space S1. In this step, the cutting edge portion 17 and the protruding portion 20 function as a reamer.

[0025] When the machining of the inner peripheral surface of the hole is completed, the cutting tool 1 is moved toward the base end side with respect to the workpiece W1 by the machine tool, and the shank 10 is removed from the workpiece W1. As a result, the desired hole is formed in the workpiece W1.

[0026] As described above, in this embodiment, when using the cutting tool 1 to form a pilot hole in the workpiece W1 and when enlarging the pilot hole to finish the hole, a force acts on the cutting tool 1 mainly in a direction along the rotation axis O1.

[0027] Note that step machining may be performed using the cutting tool 1. In step machining, a set of cutting into the workpiece W1 with the cutting tool 1 and removing the cutting tool 1 from the workpiece W1 is repeated multiple times. By performing this step machining, it is possible to make it easier to discharge chips even in the workpiece W1 from which chips are difficult to discharge.

[0028] As described above, in the cutting tool 1 of this embodiment, the lead portion 16 (the protruding portion 20 and the recessed portion 21) on the base end side of the body 15 functions as a reamer. Therefore, chips generated when the cutting edge portion 17 and the blade portion 18 form a pilot hole in the workpiece W1 are discharged toward the base end side through the tip groove 17a and the discharge space S1. The diameter of the pilot hole is then enlarged by the cutting edge portion 17 and the protruding portion 20, and the inner circumferential surface of the hole is finished. Chips generated when the inner circumferential surface of the hole is finished are discharged toward the base end side through the discharge space S1. Therefore, a hole whose inner peripheral surface is finished with a predetermined accuracy can be easily formed in the workpiece W1 without replacing the cutting tool 1 attached to the machine tool.

[0029] <Modification> In this embodiment, an example of a non-flat drill shape in which the tip of the cutting edge portion 17 and the tips of the blade portions 18 at the tip of the body 15 converge on the rotation axis O1 and form a tip angle θ1 with the rotation axis O1 as the central axis has been described, but as shown in FIG. 4, the tip of the cutting edge portion 17 and the tips of the two blade portions 18 may be structured away from the rotation axis O1. That is, as shown in the side view of the main part in FIG. 4, the cutting tool 1A according to the modified example has a flat drill shape in which the tip surface of the body 15A (a plane including the tip of the cutting edge portion 17 and the tip of the blade portion 18) is along a reference plane S4 perpendicular to the rotation axis O1. This cutting tool 1A can make the bottom surface of the hole flat when the hole to be formed in the workpiece W1 does not penetrate the workpiece W1, for example.

[0030] As another example of the shape of the flat drill, a part of the tip surface of the body 15A may be inclined at a concave angle with respect to the reference surface S4, or a ball end mill shape or a radius end mill shape in which the tip of the cutting portion 18 is hemispherical may be used.

[0031] Also, only a portion of the tip of the body 15A may be made of cubic boron nitride (CBN) or polycrystalline diamond (PCD). Even with these configurations, a certain level of rigidity can be ensured in the body 15A.

[0032] Although one embodiment of the present invention has been described in detail above with reference to the drawings, the specific configuration is not limited to this embodiment, and changes, combinations, deletions, etc. of the configuration are also included within the scope that does not deviate from the gist of the present invention. For example, the plurality of protrusions 20 and the plurality of recesses 21 may be twisted to the right, the tip groove 17a may be twisted to the left, and the blade may be a left-handed blade. In this case, the cutting tool is used by rotating in the second direction D2 during cutting. Furthermore, the surface of the cemented carbide forming the body 15 does not necessarily need to be coated with a diamond film. [Explanation of symbols]

[0033] 1,1A cutting tool 10 Shank 15,15A Body 16 Lead section 17a Tip groove 18 Blade 20 Protrusion 21 Recess D1 1st direction D2 2nd direction O1 Rotational Axis S4 reference plane T1 cross-sectional shape θ1 Tip angle

Claims

1. A shank extending along the axis of rotation, A body provided on the tip side of the shank, Equipped with, The body has a reamer portion whose base end is connected to the shank, and a drill portion at the tip of the reamer portion. The reamer portion has a polygonal shape having a cross-sectional shape perpendicular to the axis of rotation, which includes a plurality of protruding portions including cutting edges that project radially from the axis of rotation at equal intervals, and a plurality of recessed portions that are recessed toward the axis of rotation by connecting adjacent protruding portions in a concave or linear manner. The drill portion has multiple tip grooves that twist in a second direction with respect to the rotation axis. The cutting tool has multiple chip evacuation grooves formed along the recessed portion of the reamer, which are twisted in the first direction opposite to the second direction and are discontinuous and independent from the tip groove.

2. The cutting tool according to Claim 1, wherein in the cross-section of the reamer portion, the diameter D of the circumscribed circle connecting the protruding portion and the diameter d of the inscribed circle connecting the bottom portion of the recessed portion maintain a predetermined ratio, thereby ensuring both the rigidity of the cutting tool and the space for chip evacuation.

3. The cutting tool according to claim 1, wherein, in the shape of the cross-section, the relationship between the diameter D of the circumscribed circle connecting the plurality of protrusions, the diameter d of the inscribed circle connecting the bottoms of the plurality of recesses, and the distance ΔC1 between the bottom and the circumscribed circle satisfies the following conditions. ΔC1=(D-d) / 2

4. Furthermore, the cutting tool according to claim 3, wherein the relationship between the straight line connecting adjacent protrusions and the distance ΔC2 between the circumscribed circle satisfies the following conditions. ΔC1 ≥ △C2 0≦(D-d) / (2×△C2)≦1.5

5. The tip of the drill portion is a non-flat drill shape, a flat drill shape, a square end mill shape, a radius end mill shape, or a ball end mill shape. The cutting tool according to claim 1.

6. The cutting tool according to any one of claims 1 to 5, wherein at least one of the reamer portion and the drill portion is formed of cemented carbide, cubic boron nitride, or a polycrystalline diamond sintered body.

7. The cutting tool according to any one of claims 1 to 5, wherein at least one of the reamer portion and the drill portion is made of a cemented carbide with a diamond coating applied to its surface.

Images