JP7403610B1 - coated cutting tools - Google Patents

Abstract

[Problem] To realize a blade edge structure in which the hard film is hard to peel off and the blade is hard to damage. [Solution] In a coated cutting tool in which a cutting edge formed on the tip side of a tool body is covered with a hard film, a portion 28 of the cutting edge that cuts a workpiece is removed after forming a hard film. Honing suppresses initial wear of the tool and peeling of the hard film, and maintains stable machining accuracy and machined surface from the initial stage of machining. [Selection diagram] Figure 4

Description

The present invention relates to a coated cutting tool for cutting high-hardness steel and the like.

In response to the increasing hardness of the workpiece, in recent years we have developed coated cutting tools that form a hard film on the tip of the cutting tool to further increase the hardness of the tip, which is already hard, and suppress damage during cutting.・Improvements are in progress. For example, Patent Documents 1 to 3 disclose coated cutting tools with improved durability and oxidation resistance at the tool tip. Additionally, surface-coated cutting tools that perform honing before film formation are disclosed in Patent Documents 4 and 5.

In the coated cutting tool disclosed in Patent Document 1, an intermediate coating is formed on the tip of the tool that faces the object to be cut, and then a harder surface coating is formed on the intermediate coating. The film type is a composite fine particle of multiple types of elements including a metal element. The intermediate film contains carbide, and the hard surface film species contains nitride or carbonitride. What is disclosed in Patent Document 2 and Patent Document 3 are coated cutting tools in which the types of elements contained in the film are different from those in Patent Document 1.
The surface-coated cutting tool disclosed in Patent Document 4 optimizes the area ratio of voids dispersed on the surface of a hard film formed on an R-honed base material. The surface-coated cutting tool disclosed in Patent Document 5 optimizes the area ratio of macroparticles existing at the cutting edge position and the rake face position on the surface of the hard coating layer without machining the surface of the hard film. .

Patent No. 6555796 Patent No. 5673904 Patent No. 5764181 Patent No. 4895586 Patent No. 4936703

In the case of small-diameter carbide end mills, which have a relatively small diameter among coated cutting tools, coating the tool tip with a hard film is performed by physical vapor deposition, in which a layer of film is physically deposited on the surface of the tool tip in a gas phase. (Physical Vapor Deposition: PVD) method is often used. Therefore, even if the tip of a tool coated with a hard film is coated with the technology of Patent Documents 1 to 3, some of the film particles (droplets) will protrude or dent randomly on the surface, resulting in the outline of the tool. Accuracy is not necessarily uniform depending on the part, and the machining accuracy of the workpiece may not be as designed. Further, depending on the structure of the tool tip, the hard film may peel off even with the techniques disclosed in Patent Documents 4 and 5, and a portion of the tool tip may be easily damaged.

One of the objects of the present invention is to provide a coated cutting tool having a structure in which the tool contour accuracy is improved, the hard film is hard to peel off, and the tool tip is hard to be damaged. Other objects of the invention will become apparent from this disclosure.

One aspect of the present invention is that a cutting edge portion is formed on the tip side of a tool body that is rotatable around a central axis, and the cutting edge portion includes a bottom blade, a peripheral blade formed on an outer peripheral side surface of the bottom blade; and one or more blade parts each having an R edge connecting the bottom edge and the outer peripheral edge in a convex R shape, a part of the bottom edge being perpendicular to the central axis, and extending from the bottom edge to the edge of the edge. The gash surface of the part that connects to the R blade has a spiral gash shape that is a curved surface that is seamlessly twisted backward in the tool rotation direction , and the blade part is covered with a hard film, and the blade part cuts the object to be cut. The coated cutting tool is characterized in that the portion is honed after the formation of the hard film.

According to the above aspect, honing after the formation of the hard film increases tool contour accuracy, and it is possible to realize a coated cutting tool having a structure in which the hard film is difficult to peel off after film formation and the tool tip is less likely to be damaged. can.

FIG. 1 is an external perspective view showing a structural example of an end mill according to the present embodiment. (a) is a right side view of the end mill, and (b) is a bottom view. FIG. 3 is a partially enlarged view of the right side of the cutting edge. FIG. 3 is a partially enlarged view of a blade portion that constitutes a cutting edge portion. It is a front view of a cutting edge part. (a) and (b) are explanatory views showing dimensions of a cutting edge portion. It is an external perspective enlarged view of a cutting edge part. It is a partially enlarged view of the vicinity of the bottom of the long blade gash. It is a partially enlarged view of the vicinity of the gash bottom of the short blade. It is an explanatory view (photograph) showing an example of honing. It is an explanatory view (photograph) showing an example of honing. FIG. 2 is an explanatory diagram showing an example of how the end mill according to the present embodiment is used.

Hereinafter, an embodiment in which the present invention is applied to an end mill, which is an example of a hard coated cutting tool, will be described. The end mill of this embodiment is used, for example, when processing precision molds or parts using alloy tool steel (SKD11) or powder high-speed tool steel (SKH55, etc.) as a workpiece.

FIG. 1 is an external perspective view showing a structural example of an end mill according to the present embodiment. FIG. 2(a) is a right side view of this end mill, and FIG. 2(b) is a bottom view. FIG. 3 is a partially enlarged view of the right side surface of the cutting edge. FIG. 4 is a partially enlarged view of the blade portion constituting the cutting edge portion. FIG. 5 is a front view of the cutting blade. FIGS. 6(a) and 6(b) are explanatory diagrams showing dimensions of the cutting edge portion. FIG. 7 is an enlarged perspective view of the appearance of the cutting blade. FIG. 8 is a partially enlarged view of the long blade portion near the gash bottom. FIG. 9 is a partially enlarged view of the short blade portion near the bottom of the gash. 10 and 11 are diagrams (photographs) showing the surface condition of the cutting edge before and after honing. FIG. 12 is a diagram showing an example of how the end mill is used. Hereinafter, a configuration example of the end mill of this embodiment will be described with reference to these figures as appropriate.

[Example of end mill configuration]
The end mill 1 of this embodiment includes a substantially cylindrical tool body 10 illustrated by broken lines in FIGS. 1 and 2, and a distal end side of the tool body 10 illustrated by solid lines in FIGS. The tool has a cutting edge portion 20 provided at the tip of the tool that is oriented toward the cut portion rather than the predetermined portion 11 where the outer diameter is smaller. The tool body 10 and the cutting edge 20 can be made of cemented carbide, which is used in coated cutting tools of this type.

A portion of the tool body 10 closer to the proximal end of the tool than the predetermined portion 11 (a side opposite to the tip end of the tool body 10) becomes a shank portion that is attached to a machine tool (not shown). The outer diameter of the end 12 of the shank portion is formed smaller than the outer diameter of the tool body 10 in accordance with the size of the attachment mechanism on the machine tool side. Although the description will be made assuming that the outer diameter D of the cutting edge portion 20 is φ6 in this embodiment, the outer diameter D may be of any size. The outer diameter of the shank portion may be the same as the outer diameter D of the cutting edge portion 20, or may be larger than the outer diameter D of the cutting edge portion 20.

The shape and structure of the cutting edge portion 20 are the same regardless of the outer diameter D. Further, the tool body 10 and the cutting edge portion 20 have a common central axis. In this specification, the common central axis is referred to as a central axis O1. In the tool body 10, the direction perpendicular to the axis O1 is referred to as the radial direction, the direction approaching the axis O1 in the radial direction is referred to as the radially inner side or center side, and the direction away from the axis O1 is referred to as the radially outer side or outer peripheral side. Further, the direction in which the tool body 10 is rotated during cutting in the circumferential direction around the axis O1 is referred to as a tool rotation direction (indicated by an arrow). In addition, the direction in which cutting of the workpiece starts in the tool rotation direction is referred to as forward or tool rotation forward, and the opposite direction is referred to as backward or tool rotation rear. Further, the surface of the cutting edge portion 20 that faces the object to be cut may be referred to as the tip end surface, and the direction from the tip end surface to the tool base end side may be referred to as the tool base end direction or the tool base end side.

[Outline of the configuration of the cutting blade]
The cutting edge portion 20 has four blade portions 21A, 21B, 21C, and 21D that are honed after forming a hard film (FIGS. 1, 5, and 6). The four blade portions 21A, 21B, 21C, and 21D are each provided rotationally symmetrically from the radial inside to the radial outside at equal intervals in the circumferential direction around the central axis O1.
The inner terminal ends of the blade portions 21A and 21C, which are radially inner ends, each extend approximately to the central axis O1, and the slopes of flank surfaces, which will be described later, intersect with each other. The inner ends of the blade portions 21B and 21D do not reach the central axis O1, but are interrupted in the middle. The flank slopes of the blade portions 21B and 21D, which will be described later, are the same as those of the blade portions 21A and 21C. In this specification, for convenience, the blade portions 21A and 21C may be referred to as "long blades" and the blade portions 21B and 21D may be referred to as "short blades." The long blades and the short blades are arranged alternately around the central axis O1. Therefore, the portion near the inner end that could not be completely cut by the short blade is immediately cut by the long blade at the rear in the rotational direction.

As illustrated in FIGS. 5 and 6, the cutting blade 20 of this embodiment forms part of a chip evacuation mechanism between the blade 21A (long blade) and the blade 21B (short blade). Gash 24A is present. The long blade gash 24A exceeds the central axis O1. A short-blade gash 24B having a structure different from that of the gash 24A is present between the blade portion 21B (short blade) and the blade portion 21C (long blade). The short blade gash 24B does not exceed the central axis O1.
A gash 24C having the same structure as the gash 24A exists between the blade portion 21C (long blade) and the blade portion 21D (short blade). A gash 24D having the same structure as the gash 24B exists between the blade portion 21D (short blade) and the blade portion 21A (long blade).

FIG. 6(a) is a diagram in which only the tip portion of FIG. 5 is extracted, and FIG. 6(b) is an enlarged diagram of the portion 100 near the central axis O1 of the cutting blade 20 shown by a broken line in FIG. 6(a). be.
The short blade gash width (the opening interval between the gashes 24B and the gash 24D) t111 is approximately 0.25 mm, and the long blade gash intersection (the length at which the openings of the gashes 24A and 24C overlap when viewed from the left side of the figure) t112 is approximately 0.44 mm. be. However, t111 and t112 are just examples, and can be changed as appropriate depending on the size of the gash bottom, which will be described later.

[Example of blade structure]
The shape and structure other than the portion 100 shown in FIG. 6(b) are almost the same regardless of whether the blade is long or short. For example, the shape and structure of the blade portion (short blade) 21B shown in FIGS. 1 and 2 are as follows.
[Outline of short blade]
The blade part 21B has a first bottom blade part 21B1 and a second bottom blade part, each of which has a cutting edge that is an intersecting ridgeline between the outer surface and the tip surface of the tool tip and a gash surface 23B facing the cutting space in the tool rotation direction. 21B2, R blade 21B3, and outer peripheral blade 21B4. Although the rake angles of the first bottom blade portion 21B1, the second bottom blade portion 21B2, the R blade 21B3, and the peripheral blade 21B4 are negative angles (negative shapes) in this embodiment, they are not limited to negative angles. The first bottom blade portion 22B1 and the second bottom blade portion 22B2 constitute a “bottom blade” of the blade portion 21B.

The blade portion 21B has a flank surface 22B having a predetermined width (length in the circumferential direction) rearward in the tool rotation direction from each of the first bottom blade portion 21B1, the second bottom blade portion 21B2, the R blade 21B3, and the peripheral blade 21B4. . Respective flank surfaces of the first bottom blade portion 21B1 and the second bottom blade portion 21B2 are referred to as bottom blade flank surfaces 22B1 and 22B2. Further, the flank surface of the R blade 21B3 is referred to as an R blade flank surface 22B3. Further, the flank surface of the peripheral blade 21B4 is referred to as a peripheral blade flank surface 22B4. The flank surfaces 22B (22B1, 22B2, 22B3, 22B4) are inclined so that the rear side in the tool rotation direction is relatively lower than the first bottom blade part 21B1, second bottom blade part 21B2, R blade 21B3, and peripheral blade 21B4. are doing.

The width t21 (FIG. 6(a)) of the bottom blade flank surface 22B1 is approximately equal. The width of the peripheral blade flank surface 22B4 is larger than the width t21 of the bottom blade flank surface 22B1. The width of the R blade flank 22B3 gradually increases from the connection part with the bottom blade flank 22B1, and gradually expands to the width of the outer peripheral blade flank 22B4. The bottom blade flank 22B1, the R blade flank 22B3, and the outer peripheral blade flank 22B4 are smoothly continuous with each other. Therefore, it has a seamless structure.

The first bottom blade portion 21B1 is formed radially outward from the second bottom blade portion 21B2 by a length t222 at the tip end surface. For convenience, an imaginary line perpendicular to the central axis O1 on the tip side of the blade portion 21B is defined as the reference line L1 (lower part of the partially enlarged view in FIG. 4), and the angle between the first bottom blade portion 22B1 and the reference line L1 is defined as the reference line L1. 1. Let the base blade angle be θ1. The first bottom edge angle θ1 is preferably approximately the same angle as the reference line L1, that is, approximately 0° (approximately 90° with respect to a plane including the central axis O1 viewed from the rear in the tool rotation direction). "About 0°" does not necessarily have to be exactly 0°, but means that a slight error is allowed.

The second bottom blade portion 21B2 continues inward in the radial direction with respect to the first bottom blade portion 21B1, and faces toward the central axis O1. The angle between the second bottom blade portion 21B2 and the reference line L1 is defined as a second bottom blade angle θ2. It is preferable that the second bottom edge angle θ2 is slightly closer to the tool proximal end than the first bottom edge angle θ1 (lower part of the partially enlarged view in FIG. 4). For example, the second bottom edge angle θ2 is larger than the first bottom edge angle θ1 in the range of 3° or more and 10° or less (approximately 93° with respect to the plane that includes the central axis O1 when viewed from the rear in the tool rotation direction). ~100°) is preferred.
As a result, in the portion of the blade portion 21B closest to the central axis O1, a gap is created between the tip surface and the surface of the object to be cut. Therefore, it is possible to prevent the cutting load from becoming too large, and the hard film becomes difficult to separate.

Since the blade portion 21B has a first bottom edge corner 21B1 having substantially the same angle as the reference line L1 on the bottom edge, the first bottom edge corner 22B1 functions as a "wiping edge." The scraper effect of this wiper edge, that is, the effect of reducing the cusp height (an index representing machined surface roughness), improves the machining accuracy (smoothness accuracy) of the finished surface of the workpiece during cutting. This can be significantly increased compared to the case where 21B1 does not exist.

The R blade 21B3 seamlessly connects the second bottom blade part 21B2, the first bottom blade part 21B1, and the outer peripheral blade 21B4 in an arc shape or a substantially arc shape (convex R shape) (FIGS. 3 and 4). . The R blade 21B3 has a length t221 exceeding a quarter arc, and has a curvature change rate of at least less than 0.005 between the starting end and the end of the quarter arc. By connecting the machining switch from the R blade 21B3 to the peripheral blade 21B4 with the peripheral blade 21B4 at a position beyond the 1/4 arc, the starting and ending ends of the 1/4 arc all become the R contour of the R blade 21B3, and the tool contour Accuracy, especially R contour accuracy, can be maintained at a high level of accuracy.

The R blade 21B3 is formed while being gradually twisted from the tool tip side toward the tool base side (FIGS. 1 and 4). Therefore, the cutting resistance during cutting is reduced, and the machining dimensional accuracy of the workpiece can be maintained almost as designed.

The helix angle of the R blade 21B3 is preferably in the range of 0° to 40° from the viewpoint of preventing deterioration in machining efficiency and tool life. The length on a line parallel to the central axis O1 from the reference line L1 to the cutting edge end 218B is the cutting edge length t51 (FIG. 3). The cutting edge length t51 is preferably 80% to 90% of the outer diameter D, particularly about 82 to 84% to obtain a remarkable effect.

[coating]
The first bottom blade portion 21B1, the second bottom blade portion 21B2, the R blade 21B3, and the outer peripheral blade 21B4 are all honed after being coated with a hard film.

The hard film formed before honing preferably has a laminated film structure in which a plurality of types of film materials are laminated, rather than a single layer structure. In this embodiment, as an example, in the first bottom blade part 21B1, the second bottom blade part 21B2, the R blade 21B3, and the peripheral blade 21B4, a first layer is laminated on the surface of each blade part base material, and this first layer is laminated on the surface of each blade part base material. It is a hard film in which a second layer is laminated on the surface of the first layer, and a third layer is further laminated on the surface of the second layer. The first layer, the second layer, and the third layer each include a film quality in the lower layer that suppresses the growth of crystals in the adjacent upper layer. However, it is not necessarily limited to the hard film having a laminated structure as described above.

[Honing]
Honing smoothes the surface of the blade portion 21B after film formation, especially the first bottom blade portion 21B1, second bottom blade portion 21B2, R blade 21B3, outer peripheral blade 21B4, and their surroundings, and also prevents contact with the workpiece. This is a type of surface treatment method that increases the area (for example, the curvature R of the cutting edge). For example, as shown in the upper enlarged view of FIG. 4, honing is a method of machining the cutting edge 28 into a shape that intentionally sacrifices machinability.

There are various methods for honing, but in this embodiment, honing was performed by blasting the entire cutting edge 20 with a finely powdered abrasive that is harder than the tool base material of the blade 21B. Honing can be carried out by polishing, etc., but by applying fine powder, honing can be done almost uniformly over the entire area of the bottom blade, the R blade 21B3, and the peripheral blade 21B4, and the work time can be shortened. It is effective because it can be done. Further, during honing, droplets on the surface of the hard film are removed. By adjusting the blasting time, the magnitude of honing can be changed as appropriate.

Although honing increases the rigidity of the blade portion 21B, it is generally known that the cutting load increases and unexpected troubles occur. Therefore, in end mills whose main purpose is microfabrication, honing is rarely performed after forming a hard film. In this embodiment, by honing at least the bottom blade, the R blade 21B3, and the outer peripheral blade 21B4 after film formation, it was possible to suppress damage to the blade portion 21B while suppressing the cutting load. In this embodiment, in particular, honing is performed until the part of the hard film covering the cutting edge 21B that cuts the object has a curvature (referred to as "blade edge R") that is greater than or equal to the curvature of the cutting edge 21B before film formation. did. An example is shown in FIGS. 10 and 11.

The upper part of FIG. 10 is a partial enlarged photograph (scanning electron microscopy: 400x) of the first bottom blade part 21B1, first bottom blade flank surface 22B1, and bottom blade rake surface 23B after forming the hard film and before honing. be. As described above, since the first bottom blade part 21B1 is the intersection ridgeline of the gash surface 23B and the first bottom blade part 21B1, the cutting edge R of the portion that contacts the object to be cut is extremely small. In the example shown in the upper part of FIG. 10, the cutting edge R of the first bottom cutting portion 21B1 is 0.002 mm. Furthermore, it can be seen that droplets (granular protrusions) are scattered on the surface due to the film formation.

The lower part of FIG. 10 is an enlarged photograph of the part after honing (scanning electron microscopy under the same conditions). By honing, the cutting edge R of the first bottom blade portion 21B1 is increased to 0.011 mm, and droplets are removed by smoothing. As a result of the droplets being removed, the R accuracy of the outer surface of the R blade 21B also became close to a perfect circular arc, and the contour accuracy of the tool could be significantly improved.

The upper part of FIG. 11 is a partial enlarged photograph (scanning electron microscopy: 1000 times) of the R blade flank surface 22B3 after the hard film has been formed and before honing, and the lower part of FIG. 11 is a part of the part after honing. This is an enlarged photograph (taken using a scanning electron microscope under the same conditions). From FIG. 11, the droplets on the surface of the hard film have been removed, the unevenness has been significantly reduced, and the smoothness has increased. Therefore, it is possible to prevent the hard film from peeling off due to surface irregularities. In addition, initial tool wear can be suppressed, and stable machining accuracy can be maintained from the initial stage of cutting. It has been confirmed that when honing is performed before the hard film is formed as disclosed in Patent Documents 4 and 5, the hard film is peeled off in a shorter time than when honing is performed after the film is formed. This is thought to be because the surface of the base material is smoothed by honing as shown in FIG. 11, so that even if a hard film is coated afterwards, it is likely to peel off.

[Short blade gash]
The gash surface 23B formed at the front portion of the blade portion 21B in the tool rotation direction is a spiral gash (twisted gash)-shaped surface along the first bottom blade portion 21B1, the second bottom blade portion 21B2, and the R blade 21B3. This spiral gash-shaped surface extends to one bottom side 241B of the gash bottom 242B, which is recessed in the shape of a gutter at a predetermined angle with respect to the central axis O1 direction.

The bottom side 241B has a wall and a bottom that change angles in a concave R shape. The gash bottom 242B is a plane that opens halfway in the inner terminal end of the flank 22C of the blade part (long blade) 21C at the front in the tool rotation direction, and slopes at a uniform slope from the opening part to the rear end 245B ( (FIG. 9), its terminal end 245B is continuous with the flute groove 26B on the tool proximal end side. The inclination angle of the gash bottom 242B with respect to the reference line L1 (the angle with respect to a plane including the central axis O1 seen from the rear in the tool rotation direction) is larger than the inclination angle of the blade portion 21B. Therefore, air currents and chips generated during cutting are guided intensively to the gash bottom 242B, and clogging of chips near the tip surface that occurs during cutting can be suppressed.

A gash wall 243B is formed in the outer peripheral direction from the other bottom side opposite to one bottom side 241B of the gash bottom 242B, and a gash wall 243B is formed in the outer circumferential direction, and a gash wall 243B is formed on the third side of the bottom blade (a relief surface or a sweeping surface with a larger inclination angle than the bottom blade relief surface, the same applies hereinafter). ) is connected to 25B. The angle of the third surface 25B of the bottom blade in the tool proximal direction with respect to the reference line L1 is smaller than that of the gash bottom 242B. Therefore, the airflow is more easily guided to the gash bottom 242B than when the angle is not the above. The third surface 25B of the bottom blade is connected to the flank 22C of the forward (long blade) 21C in the rotational direction.

[Flute groove]
The flute groove 26B is part of a chip discharge mechanism that is connected to the terminal end 245B of the gash bottom 242B and the gash surface of the blade portion (long blade) 21C at the front in the rotational direction. The flute groove 26B twists in the direction opposite to the tool rotation direction as it goes toward the proximal end of the tool body 10, and the depth remains constant until t61, after which it gradually becomes shallower and cuts upward. Its terminal end blends into the outer periphery of the tool body 10.

The flute groove 26B has a part that continues from the gash surface 23B and the terminal end 245B of the gash bottom 242B, and a part that continues from the third face 25B of the bottom blade which has a different angle of inclination with respect to the reference line L1 than the gash surface 23B. There is a point of contact.
The length between this contact point and the reference line L1 is the optimum flute length t61 (FIG. 3). The optimum flute length t61 is preferably 60% to 80%, particularly about 70%, of the outer diameter D from the viewpoint of ensuring the rigidity of the cutting edge portion 20 at a practical level.

The angle between the bottom edge of the blade portion 21B (first bottom edge portion 21B1, second bottom edge portion 21B2) and the bottom edge of the blade portion 21C at the front in the tool rotation direction or the bottom edge of the blade portion 21A at the rear in the tool rotation direction. A21 (FIG. 3) is preferably 43° to 47°. It has been confirmed that if the angle is within this range, the frictional resistance during cutting of the workpiece is small, chip clogging is less likely to occur, and the tool tip is less likely to be damaged.

"Other short blades"
The other blade portion 21D, which is rotated by 180 degrees around the central axis O1 with respect to the blade portion 21B, has a similar shape, structure, and function. The correspondence relationship between the blade portion 21D and the blade portion 21B is as follows.
First bottom blade part 21D1...First bottom blade part 21B1, Second bottom blade part 21D2...Second bottom blade part 21B2, R blade 21D3...R blade 21B3, Peripheral blade 21B4...Peripheral blade 21B4, flank face 22D...flank face 22B, bottom blade flank 22D1...bottom blade flank 22B1, R blade flank 22D3...R blade flank 22B3, peripheral blade flank 22D4...peripheral blade Flank surface 22B4, cutting edge 218D...cutting edge 218B, gash surface 23D...gash surface 23B, gash bottom 242D...gash bottom 242B, bottom side 241B of gash bottom 241D, gash Starting end 244D of the bottom 244B, terminal end 245D of the gash bottom 245B, third surface 25D of the bottom blade 25B, flute groove 26D... flute groove 26B.

“Long blade overview”
Next, the blade portion (long blade) 21A shown in FIG. 5 and the like will be explained. The blade part (long blade) 21A differs from the blade part (short blade) 21B only in the structure near the center of the tip surface of the cutting blade part 20, and the shape of other parts is the same as the blade part (short blade) 21B. It is. Therefore, the following description will focus on the parts that are different from the blade portion (short blade) 21B. Note that regarding the corresponding configuration of the blade portion (short blade) 21B, only the reference suffix (B→A) is changed, and a redundant explanation of the configuration will be omitted.

The blade portion 21A has a first bottom blade portion 21A1, a second bottom blade portion 21A2, and R, each having a cutting edge that is an intersecting ridgeline between the outer surface and tip surface of the tool tip and the gash surface 23A facing the cutting space in the tool rotation direction. It has a blade 21A3 and a peripheral blade 21A4. The first bottom blade portion 22A1 and the second bottom blade portion 22A2 constitute a “bottom blade” of the blade portion 21A. The shape and structure of the R blade 21A3 and the peripheral blade 21A4, the helix angle of the peripheral blade 21A4, and the cutting edge length are the same as those of the blade portion 21B.

The blade portion 21A also has a flank surface having a predetermined width (length in the circumferential direction) t21 rearward in the tool rotation direction from each of the first bottom blade portion 21A1, the second bottom blade portion 21A2, the R blade 21A3, and the outer peripheral blade 21A4. 22A (FIG. 6(a)). This width t21 may be the same as the width t22 of the flank 22B of the blade portion 21B, but may be a different width. The flanks of the first bottom blade part 21A1 and the second bottom blade part 21A2 are the bottom blade flank 22A1, the flank of the R blade 21A3 is the R blade flank 22A3, and the flank of the peripheral blade 21A4 is the peripheral blade flank 22A4. . The flank 22A is inclined so as to become lower toward the base end as it goes rearward in the tool rotation direction. The inclination angle, the width of each flank, the first bottom edge angle θ1, and the second bottom edge angle θ2 are the same as those of the blade part 21B, and the inner end of the bottom edge flank 22A1 reaches near the central axis O1. are different.

[Long-blade gash]
The gash bottom 242A opens at a position where the starting end 244A of the bottom surface is longer than the inner end of the cutting edge (short blade) 21B in the forward direction of tool rotation and extends beyond the central axis O1, thereby opening the inner end of the second bottom cutting edge 21A2. The difference is that a recessed space 21AX is formed between the peripheral end and the central axis O1 (FIGS. 3 and 8). This recessed space serves as an inlet for coolant flowing into the tip surface or for discharging chips. A terminal end 245A of the gash bottom 242A is connected to a flute groove 26A on the tool base end side. The flute groove 26A is the same as the flute groove 26B of the blade portion (short blade) 21B.

The length of the plane of the gash bottom 242A that slopes at a uniform slope from the starting end 244A to the terminal end 245A is longer than that of the gash bottom 242B of the blade portion 21B. However, although the lengths are different, the angles are the same.

The gash surface 23A of the blade portion 21A is a spiral gash having the same shape as the gash surface 23B of the blade portion 21B. However, since the gash bottom 242A is longer than the gash bottom 242B as described above, the shape of the portion that becomes the gash wall is different from the gash surface 23B. The same applies to the gash wall 243A facing the gash surface 23A.

[Other long blades]
The other blade portion 21C, which is rotated by 180 degrees around the central axis O1 with respect to the blade portion 21A, has a similar shape, structure, and function. The correspondence relationship between the blade portion 21C and the blade portion 21A is as follows.
First bottom blade part 21C1...First bottom blade part 21A1, Second bottom blade part 21C2...Second bottom blade part 21A2, R blade 21C3...R blade 21A3, Peripheral blade 21C4... Peripheral blade 21A4, flank face 22C... flank face 22A, bottom blade flank 22C1... bottom blade flank 22A1, R blade flank 22C3... R blade flank 22A3, peripheral blade flank 22C4... peripheral blade Flank surface 22A4, cutting edge 218C...cutting edge 218A, gash surface 23C...gash surface 23A, gash bottom 242C...gash bottom 242A, bottom side 241C of gash bottom 241A, gash Bottom starting end 244C...same starting end 244A, gash bottom ending end 245C... same ending end 245A, bottom blade 3rd surface 25C...bottom blade 3rd surface 25A, flute groove 26C... flute groove 26A.

[How to use]
Next, an example of how the end mill 1 is used will be described with reference to FIG. 12. The end mill 1 is set in a milling chuck of the main shaft of a machine tool MC using collets with different inner diameters for each outer diameter of the shank portion. Thereafter, the tip end surface of the cutting edge portion 20 is made to face the object to be cut 500, and cutting is started. The workpiece 500 is, for example, a rectangular columnar alloy tool steel (SKD11) or powdered high-speed tool steel (SKH55, etc.). By operating the machine tool MC, the workpiece 500 can be machined into a complex shape as shown in the figure by selectively performing milling, drilling, boring, etc. with one end mill 1. .

[Modified example]
In this embodiment, the end mill 1 has been described as an example of a coated cutting tool, but as long as it is a cutting tool coated with a hard film, it is not limited to an end mill, but can be similarly applied to other drilling tools having a cutting edge. Applicable. Although the present embodiment has been described using a radius end mill as an example, it can be similarly applied to a square end mill. Further, in this embodiment, a four-blade end mill is taken as an example, but the number of blade portions may be arbitrary.

The disclosure according to this embodiment includes inventions of the following aspects.
[Aspect 1]
In the invention of aspect 1, the cutting edge formed on the tip side of the tool body is covered with a hard film, and the part of the hard film covering the cutting edge that cuts the object to be cut is formed. This is a coated cutting tool characterized by being honed after coating.
According to the invention of aspect 1, by honing after the hard film is formed, rather than before, it is possible to suppress initial wear of the tool, peeling of the hard film, and damage to the tip of the tool, resulting in stable machining from the initial stage. The machining accuracy and machined surface can be maintained. In addition, honing can remove droplets on the tool surface and improve tool contour accuracy.
Although it is desirable that the cutting edge portion not be exposed by honing, a portion of the cutting edge portion may be exposed as long as the contour accuracy of the tool tip can be maintained.

[Aspect 2]
In a second aspect of the invention, in the first aspect, the tool body is rotatable around a central axis, and the cutting blades are arranged at regular intervals from the central axis side toward the outer circumferential side when viewed from the tip surface. each of the plurality of blade parts includes a bottom blade, a peripheral blade formed on an outer peripheral side surface of the bottom blade, and connects the bottom blade and the peripheral blade in a convex R shape. The coated cutting tool has a R blade, and a portion of the bottom blade having a predetermined length that is connected to the R blade is perpendicular to the center axis.
According to the second aspect of the invention, the portion functions as a wiper blade and can produce a scraper effect. Therefore, the flatness (smoothness) of the processed surface can be improved.

[Aspect 3]
A third aspect of the invention is the coated cutting tool according to the second aspect, wherein the gash surface of the R blade has a spiral gash shape twisted backward in the tool rotation direction.
According to the third aspect of the invention, by forming the gash surface of the R blade into a seamless shape without any joints, it is possible to improve the tool contour accuracy, particularly the R contour accuracy. This enables highly accurate machining of the workpiece. Furthermore, compared to a gash shape with a straight edge, a spiral gash shape can improve cutting performance and can suppress chipping of the R blade.

[Aspect 4]
The invention according to aspect 4 is characterized in that, in the invention according to aspect 2, the R blade has a length exceeding a quarter arc, and is integrally connected to the peripheral blade at a position beyond the quarter arc. This is a coated cutting tool.
According to the invention of aspect 4, since the machining switching from the R blade to the peripheral blade is performed at a position beyond the 1/4 arc, the starting and ending ends of the 1/4 arc all become the R contour of the R blade, and the R contour Accuracy can be increased.

[Aspect 5]
In the invention according to aspect 5, in the invention according to aspect 2, the plurality of blade parts include a pair of long blades whose inner terminal ends extend to or near the central axis, and whose inner terminal ends stop midway along the central axis. The long blade and the short blade are arranged alternately in the tool rotation direction, and a part of the gash of the long blade is located inside the short blade in front of the tool rotation direction. The coated cutting tool is characterized in that a recessed space is formed between the terminal end and the central axis, and the gash of the short blade stops midway at the inner terminal end of the flank of the long blade forward in the tool rotation direction.
According to the invention of aspect 5, coolant and chips during cutting can be effectively discharged through the recessed space without reducing the strength of the long blade whose cutting resistance is greater than that of the short blade.

[Aspect 6]
A sixth aspect of the invention is the coated cutting tool according to the fifth aspect, wherein the pair of long blade gashes intersect near the central axis.
According to the invention of aspect 6, communication between adjacent short blades and gashes can be improved, and chip clogging can be more effectively prevented.

[Aspect 7]
Aspect 7 of the invention is characterized in that, in any one of aspects 1 to 6, the hard film before honing includes a first layer laminated on a surface of a blade base material and a surface of the first layer. a second layer laminated on the surface of the second surface, and a third layer laminated on the surface of the second surface, wherein each of the first layer, the second layer, and the third layer has crystals of the adjacent upper layer in the lower layer. This is a coated cutting tool characterized by comprising a film that suppresses the growth of.
According to the invention of aspect 7, the crystals can be made finer, and the hardness of the hard film can be further increased than in the case of a single-layer or two-layer structure. Therefore, by combining the characteristics of each layer, it is possible to process high-hardness materials stably with a long life.
Note that a film type having the highest toughness compared to the first layer and the second layer may be used for the third layer. Thereby, chipping of the tool tip can be more effectively suppressed.

Claims (6)

A cutting edge portion is formed on the tip side of the tool body that is rotatable around the center axis, and the cutting edge portion includes a bottom blade, an outer peripheral edge formed on the outer peripheral side surface of the bottom blade, and a bottom blade and the One or more blade portions having an R blade that connects the outer peripheral blade in a convex R shape,
The bottom blade has a spiral gash shape in which a part thereof is orthogonal to the central axis, and a gash surface of a portion connecting the bottom blade to the R blade is a curved surface seamlessly twisted backward in the tool rotation direction , and The blade part is covered with a hard film, and the part of the blade part that cuts the object to be cut is honed after the hard film is formed.
Coated cutting tools. The cutting edge portion includes a plurality of blade portions arranged at equal intervals from the central axis side toward the outer circumferential side when viewed from the tip surface,
Each of the plurality of blade portions is characterized in that a portion of the bottom blade having a predetermined length connected to the R blade is orthogonal to the central axis,
A coated cutting tool according to claim 1. The R blade has a length exceeding 1/4 arc, and is integrally connected to the peripheral blade at a position beyond the 1/4 arc.
A coated cutting tool according to claim 2. The plurality of blade parts are composed of a pair of long blades whose inner terminal ends extend to or near the central axis, and a pair of short blades whose inner terminal ends stop midway along the central axis,
The long blades and the short blades are arranged alternately in the tool rotation direction,
A part of the gash of the long blade forms a recessed space between the inner end of the short blade at the front in the tool rotation direction and the central axis,
The gash of the short blade is characterized in that it stops midway at the inner end of the flank of the long blade forward in the tool rotation direction,
A coated cutting tool according to claim 2. The pair of long blade gashes intersect near the central axis,
The coated cutting tool according to claim 4. The gash of the long blade forms the recessed space by opening at a portion where the gash bottom extends beyond the central axis of the inner end of the adjacent short blade.
The coated cutting tool according to claim 4.