Cutting insert and cutting tool

A cutting insert is provided, which can be prevented from being lifted from a tool body. A cutting insert includes two end surfaces opposed to each other, a peripheral side surface extending between the two end surfaces, a cutting edge provided at an intersecting edge between at least one of the two end surfaces and the peripheral side surface, and a fixing hole provided in an end surface direction from the first end surface to the second end surface. The peripheral side surface is provided with raised parts changing in height in the end surface direction.

BACKGROUND

Field

The present invention relates to a cutting insert and a cutting tool.

Description of Related Art

A bit (cutting tool) for a lathe is used for cutting processing and the cutting tool includes a body and a cutting insert mounted to the body. The cutting insert includes two polygonal end surfaces opposed to each other at the top and the bottom and a peripheral side surface which connects the two end surfaces, and cutting edges are formed at ridges between the peripheral side surface and the end surfaces. The cutting insert is fixed to the holder of the body by a screw or a fixing lever.

During cutting, large cutting resistance acts upon the cutting insert. The cutting resistance may cause the cutting insert to move relative to the holder of the body, which shifts the edge position of the cutting insert, and the cutting processing precision is lowered. Therefore, it has been suggested to provide a groove which fits with a body holding surface at an end surface of the cutting insert (see WO 2017/060025) or provide irregularities in the peripheral direction at the peripheral side surface of the cutting insert (see Patent Publication JP-A-2004-261883), so that turning (side slip) of the cutting insert is prevented.

SUMMARY

However, the cutting tools described above do not provide sufficient force to press the cutting insert to the side of the body holding surface (downward), and the cutting insert may be lifted during cutting. This may shift the position of the edges of the cutting insert in the vertical direction.

With the foregoing in view, it is an object of the present invention to provide a cutting insert which can be prevented from being lifted from a body (tool body) and a cutting tool.

A cutting insert according to one aspect of the present invention includes two end surfaces opposed to each other, a peripheral side surface extending between the two end surfaces, a cutting edge provided at an intersecting edge between at least one of the two end surfaces and the peripheral side surface, and a fixing hole provided in an end surface direction from a first end surface to a second end surface of the two end surfaces, the peripheral side surface has a plurality of raised parts changing in height in the end surface direction, and the raised parts each has a first inclined surface raised from the first end surface side to a center in the end surface direction and a second inclined surface raised from the second end surface side to the center in the end surface direction.

According to the aspect, the raised part changing in height is provided at the peripheral side surface of the cutting insert in the end surface direction, the tool body can press the first or second inclined surface of the raised part from above to hold the cutting insert. In this way, the cutting insert can be pressed with sufficient force to the side of the holding surface of the tool body (downward), so that the cutting insert can be prevented from being lifted from the tool body.

The two end surfaces may be formed in a polygonal shape having three or more sides, the peripheral side surface may have a plurality of peripheral side surface parts corresponding to sides of the polygonal shape of the end surfaces, and the raised part may be provided at each of the peripheral side surface parts. In this case, the cutting insert can be changed in direction and used.

A plurality of the raised parts may be provided at the peripheral side surface parts respectively. In this case, sufficient force acting to press the raised part from above by the tool body can be secured.

The fixing hole may be formed in a center of the end surface, and the end surface may be provided with a groove extending outwardly from the fixing hole toward the peripheral side surface. In this case, the protrusion of the holding surface of the tool body is fitted in the groove, so that force for pressing the cutting insert can be received at the groove. The cutting insert can be prevented from turning relative to the tool body.

The groove may be provided on an opposite side to each of the peripheral side surface parts, with the fixing hole therebetween, at the end surface. In this case, the groove is provided away from the raised part at each of the peripheral side surface parts, so that force for pressing the cutting insert can appropriately be received at the groove. The cutting insert can effectively be prevented from turning relative to the tool body.

A flat surface positioned higher than other parts may be provided at the end surface. In this case, force for pressing the cutting insert from above can be received at the flat surface of the end surface, so that the cutting insert can securely be fixed.

The flat surface may be provided between the fixing hole and each of the peripheral side surface parts along the peripheral side surface part. In this case, the flat surface is provided close to the peripheral side surface parts, so that force for pressing the cutting insert can appropriately be received at the flat surface.

The flat surface may annularly be provided at the end surface. In this case, chips are less likely to come inside beyond the flat surface, and therefore parts on the inner side of the flat surface at the end surface can be prevented from being damaged by chips.

A cutting tool according to another aspect of the present invention includes a cutting insert and a tool body holding the cutting insert, the cutting insert includes two end surfaces opposed to each other, a peripheral side surface extending between the two end surfaces, a cutting edge provided at an intersecting edge between at least one of the two end surfaces and the peripheral side surface, and a fixing hole provided in an end surface direction from a first end surface to a second end surface of the two end surfaces, the peripheral side surface has a plurality of raised parts changing in height in the end surface direction, the raised part has a first inclined surface raised from the first end surface side to a center in the end surface direction and a second inclined surface raised from the second end surface side to the center in the end surface direction, the tool body includes a first holding surface holding one end surface of the cutting insert and a second holding surface holding the peripheral side surface of the cutting insert held at the first holding surface, the second holding surface has a reversely inclined surface receding from an upper side toward the first holding surface, and the reversely inclined surface is configured to abut against the first or second inclined surface of the raised part to press the inclined surface from above.

The two end surfaces may be formed in a polygonal shape having three or more sides, the peripheral side surface has a plurality of peripheral side surface parts corresponding to sides of the polygonal shape of the end surfaces, the raised part may be provided at each of the peripheral side surface parts, and the second holding surface may abut against the raised part at one of the peripheral side surface parts to press the raised part.

The fixing hole may be formed in the center of the end surface, the end surface may be provided with a groove extending outwardly from the fixing hole toward the peripheral side surface, and the first holding surface may be provided with a protrusion to be fitted in the groove.

The groove may be provided on an opposite side to each of the peripheral side surface parts, with the fixing hole therebetween, at the end surface, and the protrusion may be provided to be fitted in the groove provided on an opposite side to the peripheral side surface part held at the second holding surface, with the fixing hole therebetween.

A flat surface positioned higher than other parts may be provided at the end surface, and the first holding surface may be provided with a flat holding surface contacted by at least a part of the flat surface.

The flat surface may be provided between the fixing hole and each of the peripheral side surface parts along the peripheral side surface part, and the flat holding surface may be provided in contact with the flat surface between the peripheral side surface part held at the second holding surface and the fixing hole.

The flat surface may annularly be provided at the end surface.

DETAILED DESCRIPTION

Hereinafter, a preferred embodiment of the present invention will be described in conjunction with the accompanying drawings. Note that the same elements are designated by the same reference characters and their description will not be repeated. The positional relation for example about the top, bottom, left, and right is based on the positional relation shown in the drawings unless otherwise specified. The dimensional ratios are not limited to those shown in the drawings. The following embodiment is an example for describing the present invention and is not intended to limit the present invention.

FIG. 1is a perspective view of a cutting tool1according to the embodiment. The cutting tool1includes a tool body10for a lathe in a square column shape elongated in one direction and a cutting insert11mounted to a tip end of the tool body10. The cutting insert11is fixed to the tool body10for example by a fastening screw12. Note that the cutting insert11may be fixed to the tool body10by a fixing lever according to another known method.

Cutting Insert

FIGS. 2 and 3are perspective views of the cutting insert11, andFIG. 4is a view of the cutting insert11from the side of a first end surface20. The cutting insert11is for example suited for profile machining using an automatic lathe. The cutting insert11has a substantially polygonal shape such as a substantially triangular shape with a thickness.

The cutting insert11includes first and second end surfaces20and21opposed to each other, a peripheral side surface22which extends between the first end surface20and the second end surface21, and cutting edges23formed at intersecting edges between the two end surfaces20and21and the peripheral side surface22. A fixing hole24is formed through the center of the cutting insert11in an end surface direction X (shown inFIG. 2) from the first end surface20to the second end surface21. The diameter of the fixing hole24is for example about in the range from 2.0 mm to 3.0 mm.

The two end surfaces20and21both have a substantially triangular shape, and the peripheral side surface22has three peripheral side surface parts30,31, and32corresponding to the sides of the triangular shapes of the end surfaces20and21. The connection part between adjacent ones among the peripheral side surface parts30,31, and32are provided with corner parts40,41, and42. As shown inFIG. 4, when viewed from the side of the end surface20, the peripheral side surface parts30,31, and32are each formed in a V-shape and have a center C in a peripheral surface direction Y (Y direction as shown inFIG. 4) which is recessed to the side of the fixing hole24(on the center side of the cutting insert11).

The peripheral side surface part30has two raised parts50that change in height in the end surface direction X. The two raised parts50are provided bilaterally symmetrically with respect to the center C of the peripheral side surface part30in the peripheral surface direction Y. As shown inFIG. 3, the raised parts50are arranged closer to the center C than the corner parts40and41(in positions closer to the center C than the apexes of the corner parts40and41).

The raised part50has a V-shaped section as shown inFIG. 5. For example, as shown inFIGS. 5 and 6, the raised part50includes a first inclined surface60gradually raised from the side of the first end surface20to the center, a second inclined surface61gradually raised from the side of the second end surface21to the center, and left and right inclined surfaces62provided on the left and right of the first and second inclined surfaces60and61in the peripheral surface direction Y. The height H (shown inFIG. 5) of the raised part50is preferably from 0.1 mm to 0.6 mm. The inclination angle α1of the first and second inclined surfaces60and61of the raised part50is preferably from 5° to 30°, for example 10°. The lateral length W (shown inFIG. 6) of the raised part50is preferably about 4 mm. The width D of the raised part50in the vertical direction is preferably about 3 mm. The width D of the raised part50in the vertical direction is in the range from 60% to 70% of the height of the cutting insert11(the distance between the end surfaces20and21) in the end surface direction X, and a flat surface (non-raised part)64is formed under and above the raised part50at the peripheral side surface part30. The raised part50is formed in the center of the cutting insert11in the end surface direction X.

The peripheral side surface parts30,31, and32are arranged with 120°-rotational symmetry around the central axis of the fixing hole24of the cutting insert11. The peripheral side surface parts31and32have the same structure as that of the peripheral side surface part30, and the peripheral side surface parts31and32each have two raised parts50similarly to the peripheral side surface part30.

As shown inFIGS. 2 to 4, the first end surface20has a chip breaker (groove)70formed on the inner side of the cutting edge23, an annular flat surface71formed on the inner side of the chip breaker, and a groove72formed on the inner side of the flat surface.

The groove72is provided so that a protrusion130, which will be described, is fitted therein. The grooves72are formed in three directions toward the corner parts40,41, and42from the fixing hole24in the center. The groove72has a length at least equal to a half of the distance from the center of the fixing hole24to the tip end of each of the corner parts40,41, and42. The length of the groove72is for example about 5 mm from the center of the fixing hole24. The groove72has a greater width on the root side (the side of the fixing hole24) than on the tip end side (on the side of the corner parts40,41, or42). The groove72is formed to have a longitudinal section recessed in a substantially V-shape as shown inFIG. 7. The inner angle α2of the V-shape of the groove72is for example about 90°. The groove72has a depth of about 0.5 mm.

As shown inFIGS. 2 to 4, the flat surface71is formed to have a substantially triangular annular shape along the peripheries of the grooves72in the three directions and the fixing hole24. More specifically, the flat surface71is formed to detour around the grooves72and the fixing hole24. The flat surface71has its highest level surface at the first end surface20. The flat surface71is provided between the peripheral side surface part30and the fixing hole24, between the peripheral side surface part31and the fixing hole24, and between the peripheral side surface part32and the fixing hole24and formed along the peripheral side surface parts30,31, and32. The flat surface71is for example a ground surface formed by grinding.

The chip breaker70is formed on the outside of flat surface71.

The second end surface21and the first end surface20are arranged with 180°-rotational symmetry around the central axis of the cutting insert11as viewed from the side of the peripheral side surface22. The second end surface21has the same structure as that of the first end surface20. More specifically, the second end surface21has a chip breaker70, a flat surface71, and a groove72similarly to the first end surface20.

The cutting edges23have for example corner cutting edges90,91, and92corresponding to the corner parts40,41, and42and intermediate connection parts93,94, and95which connect adjacent ones among the corner cutting edges90,91, and92with each other. The intermediate connection parts93,94, and95may or may not optionally function as cutting edges.

Note that the vertical angle α3(shown inFIG. 4) at each of the corner parts40,41, and42is for example preferably at least 20° and less than 60° and preferably about 35° particularly for profile machining.

The size of the cutting insert11is for example set so that the radius of the circumscribed circle of the end surface20or21is about 16 mm. The thickness of the cutting insert11(the distance between the end surfaces20and21) is for example about 3 mm. The roundness (corner radius) of the corner parts40,41, and42is for example about 0.4 mm, preferably from 0.2 mm to 1.2 mm. The length of the cutting edge23from each corner of the corner parts40,41, and42to one side in the peripheral side surface direction is for example about 5 mm, preferably from 3 mm to 10 mm. The material of the cutting insert11may be selected from, but not limited to, any of hard materials such as cemented carbide, cermet, ceramics, and a sintered body containing cubic boron nitride or any of the hard materials having a surface coated with a PVD or CVD coating film, or monocrystalline diamond or a sintered body containing diamond.

Tool Body

As shown inFIGS. 8 and 9, the tool body10includes a holder100which holds the cutting insert11at a tip end thereof. The holder100has a first holding surface110which holds the first or second end surface20or21of the cutting insert11and a second holding surface111which holds any of the peripheral side surface parts30,31, and32of the cutting insert11held at the first holding surface110.

The first holding surface110has for example a substantially triangular shape in conformity with the outer shape of the cutting insert11. The second holding surface111extends upright from the end of the first holding surface110.

The second holding surface111is formed to have a substantially V shape in conformity with the shape of the peripheral side surface parts30,31, and32of the cutting insert11when viewed from above. As shown inFIG. 10, the second holding surface111has a reversely inclined surface120which recedes inwardly from the upper side to the first holding surface110. The inclination angle of the reversely inclined surface120(the inclination angle of the first holding surface110with respect to the vertical surface) α4corresponds to the inclination angle α1of the inclined surface60or61of the raised part50and is an angle equal to the inclination angle α1, for instance, about 10°. The reversely inclined surface120abuts against the first or second inclined surface60or61of the raised part50and can press the inclined surface60or61from above.

As shown inFIGS. 8 and 9, the first holding surface110has the protrusion130which is fitted in the groove72of the cutting insert11, a flat holding surface131which receives the flat surface71of the cutting insert11, and a fixing part132corresponding to the fixing hole24of the cutting insert11.

The fixing part132is a screw hole for fixing in which a fastening screw12is screwed and formed substantially in the center of the first holding surface110.

The protrusion130is provided at the first holding surface110on the opposite side to the second holding surface111with the fixing part132therebetween. The protrusion130is provided to extend from the fixing part132as the origin in a direction away from the second holding surface111(in the tip end direction of the tool body10). The protrusion130is formed in a ridge shape to conform to the shape of the groove72. As shown inFIG. 7, the upper surface of a longitudinal section of the protrusion130has an upward raised arc shape which can be fitted into the V-shape of the groove72.

As shown inFIGS. 8 and 9, the flat holding surface131is formed between the second holding surface111and the fixing part132. The flat holding surface131is formed to have a substantially square shape having a width from the second holding surface111to the side of the fixing part132. The flat holding surface131is formed to conform to the second holding surface111when viewed from above. The fixing part132of the first holding surface110and the part133having the protrusion130are positioned one step lower than the flat holding surface131.

Assembling of Cutting Tool

When the cutting insert11is mounted to the tool body10, the cutting insert11is placed at the holder100of the tool body10. At the time, as shown inFIG. 10, one of the end surfaces of the cutting insert11, the first end surface20for example is directed to face downward to be placed on the first holding surface110, and the peripheral side surface part30for example is placed on the second holding surface111.

The second holding surface111abuts against the two raised parts50of the peripheral side surface part30and presses the raised parts50from above. More specifically, the reversely inclined surface120of the second holding surface111and the first inclined surface60arranged above the raised parts50abut against each other, so that the reversely inclined surface120presses the first inclined surface60from above.

The flat surface71of the first end surface20is placed on the flat holding surface131of the first holding surface110. As shown inFIG. 7, the protrusion130is fitted into the groove72of the first end surface20.

In this state, the fastening screw12shown inFIG. 9for example is inserted into the fixing hole24of the cutting insert11and the fixing part132of the tool body10, and the fastening screw12is fastened as shown inFIG. 1, so that the cutting insert11is fixed to the tool body10.

Note that when any of the other peripheral side surface parts31and32is directed to face the second holding surface111, the cutting insert11is held similarly to the case of the peripheral side surface part30described above. When the second end surface21is directed to face the side of the first holding surface110, the cutting insert11is held similarly to the case of the first end surface20described above. When the second end surface21is held at the first holding surface110, any of the peripheral side surface parts30,31, and32can be selected to be held at the second holding surface111. Therefore, there are six patterns for holding the cutting insert11with respect to the tool body10.

According to the embodiment, the raised parts50which change in height in the end surface direction X are formed at the peripheral side surface22of the cutting insert11, so that the tool body10can press the raised parts50from above to hold the cutting insert11. In this way, the cutting insert11is pressed with sufficient force toward the first holding surface110of the tool body10(downward), so that the cutting insert11can be prevented from being lifted from the tool body10.

The raised part50includes the first inclined surface60which gradually rises from the side of the first end surface20to the center in the end surface direction X and the second inclined surface61which gradually rises from the side of the second end surface21to the center in the end surface direction X. In this way, the tool body10can press the first or second inclined surface60or61and thus can appropriately press the cutting insert11with sufficient force.

The two end surfaces20and21are formed to have a substantially triangular shape, the peripheral side surface22has a plurality of peripheral side surface parts30,31, and32corresponding to the sides of the end surfaces20and21, and the raised parts50are provided at each of the peripheral side surface parts30,31, and32. In this way, the cutting insert11can be changed in direction and used.

A plurality of raised parts50are provided at the peripheral side surface parts30,31, and32, and therefore sufficient force is secured for pressing the raised parts50from above by the second holding surface111of the tool body10.

The end surfaces20and21are each provided with the groove72which extends outwardly to the peripheral side surface22from the fixing hole24, and force for pressing the cutting insert11can appropriately be received by the grooves72by fitting the grooves72in the protrusions130of the first holding surface110of the tool body10. The cutting insert11can be prevented from turning relative to the tool main body10.

The grooves72are provided at the end surfaces20and21in locations on the opposite side to the peripheral side surface parts30,31, and32with the fixing hole24therebetween. In this way, the grooves72are positioned away from the raised parts50of the peripheral side surface parts30,31, and32, so that force for pressing the cutting insert11can appropriately be received at the raised parts50and the grooves72apart from each other. The cutting insert11can efficiently be prevented from turning relative to the tool main body10.

The end surfaces20and21each have the flat surface71positioned higher than the other part. In this way, the flat surface71of the cutting insert11comes into close contact with the first holding surface110of the tool main body10, so that force acting to press the cutting insert11from above by the second holding surface111of the tool main body10is received at the flat surface71and the cutting insert11can securely be fixed.

The flat surface71may be provided along the peripheral side surface parts30,31, and32between the fixing hole24and the peripheral side surface parts30,31, and32. In this case, the flat surface71is close to the peripheral side surface parts30,31, and32, and therefore the force acting to press the cutting insert11can appropriately be received at the flat surface71.

The flat surface71is formed annularly at the end surfaces20and21, and therefore chips are less likely to come inside beyond the flat surface71. In this way, parts on the inner side of the flat surface71at the end surfaces20and21such as the grooves72can be prevented from being damaged by chips.

Although the preferred embodiment of the present invention has been described with reference to the accompanying drawings, the same is not intended to limit the present invention. It is understood that variations and modifications would be apparent to those skilled in the art within the scope of the concept recited in the claims and that the variations and modifications naturally fall within the technical scope of the present invention.

In the cutting tool1, the cutting insert11is fixed to the tool main body10using the fastening screw12but the cutting insert may be fixed by any of other methods. For example, the cutting insert11may be fixed by lever locking or using a wedge, a presser piece, or an eccentric pin.

The cutting insert11according to the embodiment has a triangular shape but may have any of other polygonal shapes such as a square shape and a pentagonal shape. While the cutting tool1according to the embodiment is adapted for use in a lathe, the cutting tool may suitably be used for milling.

Example

Experiments were carried out for different values of the angle α1and the height H of the raised parts50at the peripheral side surface22of the cutting insert11. The cutting insert11was arranged inclined in the tool main body10so that the clearance angle is about 6°. Note however that the clearance angle was about 20° only for the raised part50having an angle of 50° (and a height of 1 mm) in order to prevent the raised part50from colliding against a workpiece. As for the other conditions, the material of the workpiece was carbon steel (S45C), the machining diameter ϕ was 100 mm, the machining length was 500 mm, the cutting was conducted by wet cutting (with a water-soluble cutting lubricant), the cutting speed Vc was 300 m/min, the maximum cutting depth ap was 3 mm, and the feed f was 0.4 mm/rev. In the results, evaluation A represents a result with no chippings generated after ten experiments, evaluation B represents a result with one or two chippings after ten experiments, evaluation C represents a result with three to five chippings after ten experiments, and evaluation D represents a result with six or more chippings after ten experiments. The results of the experiments are given in Table 1.

The present invention is useful in providing a cutting insert which can be prevented from being lifted from a tool main body.