JP7211077B2 - Cutting inserts and indexable cutting tools - Google Patents

Description

The present invention relates to a cutting insert used for finishing, for example, an engine crankshaft, and an indexable cutting tool (indexable cutting tool) to which such a cutting insert is detachably attached.

As such a cutting insert and indexable cutting tool, the inventors of the present invention disclosed in Patent Document 1 that a holder that extends along a first direction and has a pedestal at its tip, and a cutting tool that is attached to this pedestal. The cutting insert comprises an insert and a first fixing screw and a second fixing screw for fixing the cutting insert to the base, the cutting insert being provided with a rake face facing in a second direction perpendicular to the first direction. The pedestal has a side portion facing a third direction perpendicular to the first and second directions, and the side portion has openings in the first and third directions for the cutting insert. It is proposed that a housing recess for housing a part of the housing is provided.

The housing recess has a bottom surface facing the second direction and side wall surfaces facing at least one of the first and third directions. A first screw hole and a second screw hole are provided, and the first and second fixing screws are inserted into the first and second screw holes, respectively, with the tips thereof contacting the main surface of the insert, and the first fixing screw. A screw presses the cutting insert against the bottom surface and the sidewall surface, a second fixing screw presses the cutting insert against the bottom surface, and the first and second fixing screws are arranged side by side along the first direction.

JP 2018-149617 A

By the way, as described in Patent Document 1, the width of the journal portion of the crankshaft, which is machined by the above-mentioned indexable cutting tool, has been reduced due to the downsizing of engines in recent years. Accordingly, there is a demand for an indexable cutting tool capable of cutting even when the distance between adjacent crank arms is small. In this regard, in the indexable cutting tool described in Patent Document 1, even if the width of the tip portion of the holder is reduced, the cutting insert can be attached with sufficient fixing force by the first and second fixing screws. .

However, the narrowing of the interval between the adjacent crank arms leads to difficulty in smooth discharge of chips generated during finish machining of the journal portion between the crank arms. In particular, in the indexable cutting tool described in Patent Document 1, the cutting insert accommodated in the accommodation recess of the pedestal portion of the holder has a rake surface, which is the main surface of the insert, which is located on the upper jaw-shaped portion of the pedestal portion. It is fixed by being pressed by screwed first and second fixing screws, and the upper jaw overhangs the rake face of the cutting insert. As a result, chips that have nowhere to go between the narrow crank arms may get entangled in the upper jaw and damage the holder, or the finished journals and crank arms may be damaged by the chips.

SUMMARY OF THE INVENTION The present invention has been made under such a background, and an object of the present invention is to smoothly discharge chips even when performing finish machining of a crankshaft having a narrow journal portion width while ensuring mounting strength of a cutting insert. It is an object of the present invention to provide a cutting insert and an indexable cutting tool.

In order to solve the above-mentioned problems and achieve such objects, the cutting insert of the present invention comprises an insert body in the form of a square plate, and the insert body is placed at the center of the two square faces of the insert body. A mounting hole is provided therethrough, and the insert body has a shape that is 180° rotationally symmetrical with respect to the center line of the mounting hole, and has a shape that is inverted symmetrically with respect to the two quadrilateral faces. the four sides of the insert body arranged on the periphery have two first sides facing away from each other and two second sides located between the two first sides; The two first side surfaces are parallelogram-shaped when viewed from the direction facing the first side surfaces, and each of the first side surfaces is a rake surface. A cutting edge having a corner edge is formed at an acute-angled corner portion of the rake face, and the corner edge of these cutting edges is located diagonally between the two quadrilateral surfaces and diagonally between the two second side surfaces. and the second side surface is provided with convex portions at two locations connected to the acute-angled corner portions of the two first side surfaces, respectively, in a direction facing the second side surface. viewed from above, each of the two protrusions is the first side surface where the protrusions of the two first side surfaces are connected in a direction along the intersection ridgeline between the second side surface and the quadrilateral surface. The two first side surfaces serving as the rake surfaces have a stepped surface facing an obtuse-angled corner portion of the first side surface facing away from the edge of the insert body. A flat surface perpendicular to the rectangular surface protruding in the direction is formed .

Further, in the indexable cutting tool of the present invention, a recessed insert mounting seat that is recessed one step from the side surface of the tool body is formed at the tip of the plate-shaped tool body. An indexable cutting tool that is detachably mounted by a clamp screw that is inserted into the mounting hole of the cutting insert and screwed into the insert mounting seat, wherein the cutting insert includes a rectangular plate-shaped insert body, The mounting hole passing through the insert body is opened in the center of the two square faces of the insert body. The four sides of the insert body arranged around the two quadrangular faces are two first sides facing opposite to each other and the two first sides facing each other. and two second side surfaces positioned between the side surfaces, the two first side surfaces being parallelogram-shaped when viewed in a direction facing the first side surfaces, and the two second side surfaces 1, each first side face serves as a rake face, and cutting edges having corner edges at acute-angled corners of the rake faces are formed. It is arranged at the diagonal position of the surface and the diagonal position of the two second side surfaces. When viewed from the direction facing the second side surface, the two protrusions are arranged in the direction along the intersection ridgeline between the second side surface and the quadrilateral surface. a step surface facing an obtuse-angled corner portion of the first side surface facing away from the first side surface on which the protrusions are connected; a bottom surface with which one of the two first side surfaces of the insert body abuts; a first wall surface with which one of the two square surfaces of the insert body abuts; The tip of the tool body with which the part connected to the acute-angled corner portion of the rake face abuts on the first side surface opposite to the one first side surface that abuts on the bottom surface, out of the two second side surfaces. a second wall surface facing the side, and the second wall surface is formed in a slanted surface shape that approaches the first wall surface toward the rear end side of the tool body, and the first wall surface has a Screw hole into which the above clamp screw is screwed is formed between the bottom surface and the second wall surface and is oriented toward the rear end side of the tool body among the two second side surfaces of the insert body and abuts against the second wall surface. A concave portion is formed to accommodate the convex portion on the one first side surface side that is brought into contact with the bottom surface of the one second side surface that is to be pressed. It is characterized in that the insert mounting seat is pulled in and mounted in a direction in which the bottom surface and the second wall surface intersect when viewed from the direction facing the first wall surface of the insert mounting seat.

In the cutting insert and the indexable cutting tool configured in this way, the cutting insert is clamped by a clamp screw that is inserted into a mounting hole that opens in the center of two square faces of the insert body and passes through the insert body. Since it is attached to the insert mounting seat of the main body, one of the two first side surfaces that face opposite sides of the side surfaces around the square surface serves as a rake surface to rotate the work material (for example, the journal part of the crankshaft). It is possible to prevent the upper jaw of the base of the holder and the fixing screw from being overlaid on the rake face when the rake face is opposed in the direction.

Therefore, chips generated by the cutting edge on the tip side of the tool body on the first side surface, which is the rake face, are entangled in the pedestal and fixing screws of the holder, resulting in damage to the tool body and finishing machining. It is possible to prevent chips from contacting and scratching the journals and crank arms, and it is possible to smoothly discharge chips from between the crank arms, which have become narrower due to downsizing, while processing chips. Become.

In addition, in the cutting insert having the above configuration, the insert body has a 180° rotationally symmetrical shape with respect to the center line of the mounting hole, and has an inverted symmetrical shape with respect to the two quadrangular surfaces, and the two first side surfaces are rake surfaces. has a parallelogram shape, one of the two acute corners on one of the two first side surfaces, which are rake faces facing each other in the direction of rotation of the work material, is When the corner edge of the cutting edge is located on the side opposite to the first wall surface of the insert mounting seat, the other acute-angled corner opposite to this one acute-angled corner is the corner edge. is positioned on the first wall surface side.

Since the insert body of the cutting insert is pulled in by the clamp screw in the direction in which the bottom surface of the insert mounting seat intersects the second wall surface, the insert body is pulled into the first position of the insert mounting seat. one of the two square surfaces in contact with the wall surface, and a portion of the second side surface of the insert body in contact with the second wall surface that is connected to the other one acute-angled corner portion, It is attached so as to be pressed against the first and second wall surfaces. Therefore, since the cutting insert is attached to the insert mounting seat in such a manner that the wedge is driven into the insert mounting seat, the mounting strength to the tool body is ensured, and stable cutting can be performed.

Furthermore, in the cutting insert configured as described above, the second side surface is provided with two convex portions that are connected to the acute-angled corner portions of the two first side surfaces, respectively. The insert mounting seat of the indexable cutting tool has a stepped surface facing the obtuse-angled corner portion of the first side surface in a direction along the intersecting ridgeline between the second side surface and the quadrilateral surface. A recess is formed between the second wall surface and the bottom surface to accommodate the protrusion on the first side surface of the second side surface of the insert body that contacts the bottom surface.

For this reason, when a force acts to rotate the insert body around the center line of the mounting hole due to the load acting on the cutting edge used for cutting, even if the clamp screw is loosened, the convex portion is thus replaced by the concave portion. By being housed in and engaged with the insert body, it is possible to prevent the insert body from falling off from the insert mounting seat.
In addition, by forming a flat surface perpendicular to the rectangular surface protruding outward of the insert body from the cutting edge on the two first side surfaces, the two first side surfaces of the insert body are formed. Of these, the flat surface abuts against the bottom surface of the insert mounting seat. The contact can be stably made, and the mounting strength can be further improved.

Here, the stepped surface of the convex portion is positioned with respect to the intersection ridgeline between the second side surface and the quadrilateral surface, which continues to the obtuse angle corner portion of the first side surface, when viewed from the center line direction of the mounting hole. preferably extend in the intersecting direction at an angle in the range of 90° to 135°. This angle is less than 90°, and as the stepped surface protrudes outward from the insert body, the cross ridge line is directed toward the obtuse corner of one of the two first side surfaces. On the other hand, if it extends in a V shape, there is a risk that the convex portion will be chipped. Also, if this angle is an obtuse angle larger than 135°, there is a risk that the effect of preventing the insert body from coming off cannot be expected when a force is applied to rotate the insert body around the center line of the mounting hole as described above.

INDUSTRIAL APPLICABILITY As described above, according to the present invention, it is possible to smoothly discharge chips while ensuring the mounting strength of the cutting insert, even when finishing machining is performed on a crankshaft having a journal portion with a small width. It is possible to perform stable cutting without incurring damage to the tool body or degrading the finish-machined surface.

It is a perspective view showing one embodiment of the cutting insert of the present invention. FIG. 2 is a side view of the embodiment shown in FIG. 1 as viewed from a direction facing the rectangular surface of the insert body (centerline direction of the mounting hole); FIG. 2 is a plan view of the embodiment shown in FIG. 1 viewed from a direction facing a first side surface serving as a rake surface of the insert body; 2 is a front view of the embodiment shown in FIG. 1 viewed from a direction facing a second side surface of the insert body; FIG. FIG. 3 is a ZZ cross-sectional view in FIG. 2 ; Fig. 2 is a right side view of the tool body in one embodiment of the indexable cutting tool of the present invention; FIG. 7 is a left side view of the tool body shown in FIG. 6; FIG. 7 is a plan view of the tool body shown in FIG. 6; FIG. 7 is a bottom view of the tool body shown in FIG. 6; FIG. 7 is a front view of the tool body shown in FIG. 6; FIG. 7 is a rear view of the tool body shown in FIG. 6; Figure 12 is a side view of a clamp screw for attaching the cutting insert of the embodiment shown in Figures 1-5 to the tool body shown in Figures 6-11; 1 to 5 is attached to the tool body shown in FIGS. 6 to 11 with a clamp screw shown in FIG. 12, showing an embodiment of the indexable cutting tool of the present invention. It is a perspective view. Figure 14 is a right side view of the embodiment shown in Figure 13; Figure 14 is a left side view of the embodiment shown in Figure 13; Figure 14 is a plan view of the embodiment shown in Figure 13; Figure 14 is a bottom view of the embodiment shown in Figure 13; Figure 14 is a front view of the embodiment shown in Figure 13; Figure 14 is a rear view of the embodiment shown in Figure 13; FIG. 20 is a plan view showing a workpiece (crankshaft) to be cut by the indexable cutting tool of the embodiment shown in FIGS. 13 to 19; FIG. 21 is a plan view showing a first step in cutting the work material shown in FIG. 20 with the indexable cutting tool of the embodiment shown in FIGS. 13 to 19; 21. It is ZZ sectional drawing in FIG. FIG. 21 is a plan view showing a second step in cutting the work material shown in FIG. 20 with the indexable cutting tool of the embodiment shown in FIGS. 13 to 19; FIG. 21 is a plan view showing a third step in cutting the work material shown in FIG. 20 with the indexable cutting tool of the embodiment shown in FIGS. 13 to 19; FIG. 6 is a perspective view showing a modification of the cutting insert of the embodiment shown in FIGS. 1 to 5; FIG. 26 is a side view of the modified example shown in FIG. 25 viewed from the direction facing the rectangular surface of the insert body (center line direction of the mounting hole); FIG. 26 is a plan view of the modification shown in FIG. 25 viewed from the direction facing the first side surface serving as the rake surface of the insert body; FIG. 26 is a front view of the modification shown in FIG. 25 viewed from the direction facing the second side surface of the insert body; FIG. 27 is a ZZ sectional view in FIG. 26;

1 to 5 show one embodiment of the cutting insert of the present invention, and FIGS. 6 to 11 show the tool body in one embodiment of the indexable cutting tool of the present invention, 12 shows a clamping screw for attaching the cutting insert of the embodiment shown in FIGS. 1-5 to the tool body shown in FIGS. 6-11, and FIGS. 5 shows an embodiment of the indexable cutting tool of the present invention in which the cutting insert of the embodiment shown in FIG. 5 is attached to the tool body shown in FIGS. 6 to 11. FIG.

Also, FIG. 20 shows a work material (crankshaft) to be cut by the indexable cutting tool of this embodiment, and FIGS. 19 shows each step of cutting with the indexable cutting tool of the embodiment shown in FIG.

The cutting insert of this embodiment includes a rectangular plate-shaped insert body 1 made of hard material such as cemented carbide. The insert body 1 has a rectangular plate shape in detail, and more specifically has a substantially square plate shape as shown in FIG. Therefore, the insert body 1 has two quadrilateral faces (square faces) 2 on the front and back planes, two first side faces 3 arranged around the two quadrilateral faces 2 and facing opposite to each other. It has two second side surfaces 4 extending in a direction perpendicular to the first side surfaces 3 between the two first side surfaces 3 and facing opposite to each other.

A mounting hole 5 having a circular cross section penetrating through the insert body 1 is opened at the center of the two square faces 2 . As shown in FIG. 5, the mounting hole 5 is formed such that its inner diameter gradually or stepwise decreases from the openings to the two square faces 2 toward the inside of the insert body 1 . The insert body 1 is formed in a shape that is 180° rotationally symmetrical with respect to the center line O of the mounting hole 5 and is also formed in a shape that is reversed and symmetrical with respect to the two quadrangular surfaces 2 .

The two first side surfaces 3 are rake surfaces and are formed in a parallelogram shape as shown in FIG. A cutting edge 6 having a corner edge 6a at an acute-angled corner C of the parallelogram formed by the first side surface 3 is formed on the edge of the first side surface 3 serving as the rake face. Therefore, these cutting edges 6 have their corner edges 6a positioned diagonally between the two square faces 2 as shown in FIG. 2 and diagonally between the two second side faces 4 as shown in FIG. being arranged in a position, i.e. alternately on two first side faces 3 opposite each other in the circumferential direction of the two quadrilateral faces 2 and in the circumferential direction of the two second side faces 4 become.

The corner edge 6a is formed in a convex curved shape such as a convex circular arc as shown in FIG. Also, the portion of the cutting edge 6 extending along the crossing ridgeline between the first side surface 3 and the second side surface 4 is a straight front cutting edge 6b that is also inclined when viewed from the direction facing the first side surface 3. , and the intersection ridgeline portion between the first side surface 3 and the quadrangular surface 2 is a straight side edge 6c extending in a direction intersecting the end cutting edge 6b at an acute angle.

Therefore, the front flank 4a of the cutting edge 6 connected to the front cutting edge 6b on the second side surface 4 and the lateral flank 2a of the cutting edge 6 connecting to the side edge 6c on the quadrangular surface 2 are also arranged in directions intersecting at an acute angle. will be extended. The front flank 4a and the side flank 2a are formed flat. 2 and 4, the end cutting edge 6b and the side cutting edge 6c are formed on the first side surface 3 opposite to the first side surface 3 on which the cutting edge 6 is gradually formed as they separate from the corner edge 6a. It extends so as to incline toward the side.

Further, the first side surface 3 is formed with a groove-shaped chip breaker 3a extending along the cutting edge 6 in the range where the cutting edge 6 is formed. A flat surface 3b perpendicular to the rectangular surface 2 is formed on the first side surface 3 other than the chip breakers 3a. It is formed at a position protruding toward the side.

Furthermore, the second side surface 4 is provided with two protrusions 7 at two locations connected to the acute-angled corner portions C of the two first side surfaces 3 , and these two protrusions 7 of the first side surface 3 each have a stepped surface 7a facing the obtuse corner portion D of the first side surface 3 in the direction along the intersection ridgeline between the second side surface 4 and the quadrangular surface 2 . That is, the second side surface 4 has an obtuse angle corner portion D of one of the two first side surfaces 3 to the other first side surface 3 at the intersection ridge with the quadrangular surface 2 . A convex portion 7 having a stepped surface 7a that protrudes outward from the insert body 1 toward an acute-angled corner portion C at 3 is formed.

The outer peripheral surface of the convex portion 7 serves as a corner flank surface 7b of the other first side surface 3 connected to the corner cutting edge 6a to form a convex cylindrical surface. It is formed at the boundary between the planar front flank 4a connected to the end cutting edge 6b of one first side surface 3 and the outer peripheral surface of the projection 7. As shown in FIG. This step surface 7a is a front flank surface 4a of the second side surface 4, which is a portion continuing to the obtuse corner portion D of the first side surface 3 as shown in FIG. and the quadrangular surface 2 at an angle θ in the range of 90° to 135°. Especially in this embodiment, the angle θ is an obtuse angle.

The cutting insert configured in this manner is detachably attached to the insert mounting seat 12 formed at the tip of the tool body 11 shown in FIGS. 1 to constitute one embodiment of the indexable cutting tool of the present invention shown in FIGS. The cutting insert and indexable cutting tool of this embodiment are so-called right-hand cutting inserts and indexable cutting tools.

The cutting edge portion 11A on the tip side (left side in FIGS. 6, 8 and 9; right side in FIG. 7) is made of steel or the like. One side surface of the shank portion 11B (the lower side surface in FIG. 8, the upper side surface in FIG. 9, the right side surface in FIG. 10) of the shank portion 11B on the left side) is a substantially rectangular shape that is biased toward the 11a side and made thinner than the shank portion 11B. is formed into a plate shape.

The insert mounting seat 12 is formed at the upper end (upper end in FIGS. 6 and 10) of one side surface 11a of the cutting edge portion 11A so as to be recessed from the one side surface 11a. In addition, on the one side surface 11a of the tool body 11 and the other side surface 11b facing the opposite side of the one side surface 11a, these side surfaces 11a, A recessed arcuate stepped portion 11c is formed on the rear end side of the tool body 11 in a side view facing the recessed portion 11b.

The insert mounting seat 12 has a planar bottom surface 12a that extends perpendicularly to the one side surface 11a of the tool body 11 and faces the upper end of the tool body 11, and one side surface 11a that is perpendicular to the bottom surface 12a. a flat first wall surface 12b recessed one step from the bottom surface 12a, and an inclined flat surface extending toward the front end side of the tool body 11 toward the rear end side of the tool body 11 so as to approach the first wall surface 12b. and a second wall surface 12c. A screw hole 12d into which the clamp screw 13 is screwed is formed in the first wall surface 12b.

As shown in FIG. 6, the bottom surface 12a of the insert mounting seat 12 is directed toward the lower side of the tool body 11 (the lower side in FIGS. 6, 7, 10, and 11) as it goes toward the tip side of the tool body 11. While extending with a slight inclination, the first wall surface 12b extends with a slight inclination toward the one side surface 11a as shown in FIG. 12 d of screw holes are formed so that the centerline may become perpendicular|vertical to this 1st wall surface 12b.

Further, at the corner where the bottom surface 12a of the insert mounting seat 12 and the first wall surface 12b intersect and the corner where the first wall surface 12b and the second wall surface 12c intersect, A recess 12e having a circular cross section is formed as a relief for preventing interference. Further, a recess 12f in which the protrusion 7 of the insert body 1 is accommodated is formed in the corner between the bottom surface 12a and the second wall surface 12c. Furthermore, the clamp screw 13 has a head 13a and a male threaded portion 13b. It is formed in a truncated cone shape around the center line of 13b.

With such an insert mounting seat 12, the insert body 1 of the cutting insert abuts one of the two rectangular surfaces 2 against the first wall surface 12b and one of the two first side surfaces 3. A state in which the flat surface 3b of one first side surface 3 is in contact with the bottom surface 12a, and in this way, one rectangular surface 2 and one first side surface 3 are in contact with the first wall surface 12b and the bottom surface 12a. , one of the two second side surfaces 4 directed toward the rear end of the tool body 11 is brought into contact with the second wall surface 12c so as to be seated. At this time, the convex portion 7 of the second side surface 4 on the side of the first side surface 3 that abuts the bottom surface 12 a is accommodated in the concave portion 12 f of the insert mounting seat 12 . In this seated state, the side cutting edge 6c is slightly inclined toward the other side surface 11b of the tool body 11 toward the rear end side of the tool body 11. As shown in FIG.

Here, in this seated state, the center line of the screw hole 12d of the insert mounting seat 12 is slightly eccentric to the center line O of the mounting hole 5 of the insert body 1 toward the concave portion 12f. is formed as When the clamp screw 13 inserted through the mounting hole 5 is screwed into the screw hole 12d in the state where the insert body 1 is seated in this manner, the back surface 13c of the head 13a of the clamp screw 13 is pushed into one side of the tool body 11. The insert body 1 contacts the tapered surface of the opening of the mounting hole 5 on the side of the rectangular surface 2 of the insert body 1 facing the side surface 11 a , and the male threaded portion 13 b is slightly bent, and the reaction force causes the insert body 1 to move toward the insert mounting seat 12 . When viewed from the direction facing the first wall surface 12b, the bottom surface 12a and the second wall surface 12c intersect and are pulled in the direction toward the recess 12f to be detachably attached.

The indexable cutting tool to which the cutting insert is attached in this manner performs finish machining from the outer peripheral surface of the journal portion W1 of the crankshaft W, which is the work material, to the inner peripheral portion of the inner surface of the crank arm W2 as shown in FIG. At the corner where the outer peripheral surface of the journal W1 intersects with the inner surface of the crank arm W2, an annular groove W3 recessed inwardly is formed by profiling.

The crankshaft W is rotatably supported in the rotation direction T shown in FIG. 22 around the center line X of the journal portion W1. Also, in the indexable cutting tool, the cutting edge portion 11A is directed toward the outer peripheral surface of the journal portion W1 and is opposite to the one first side surface 3 of the insert body 1 that abuts the bottom surface 12a of the insert mounting seat 12. The first side surface 3 of is supported so as to face the rotation direction T of the crankshaft W as a rake surface.

The indexable cutting tool supported in this manner moves from the central portion of the journal portion W1 in the width direction (center line X direction) to the journal portion by advancing the tool body 11 as indicated by the white arrow in FIG. A cutting edge 6 is cut into the outer peripheral surface of W1. 23, the indexable cutting tool is sent toward one side surface 11a of the tool body 11 in the direction of the center line X, and the journal portion W1 is formed by drawing with the corner edge 6a. After the outer peripheral surface is finished, the inner peripheral portion of the inner surface of the crank arm W2 is finished by being fed to the outer peripheral side of the journal portion W1 and drawn by the side edge 6c.

Further, when the outer peripheral surface of the journal portion W1 and the inner peripheral portion of the inner surface of the crank arm W2 are finished in this way, the corner edge 6a is formed on the outer peripheral surface of the journal W1 as indicated by the white arrow in FIG. The crank arm W2 is reciprocally moved in a V-shape toward the corner where the inner peripheral portion of the inner surface of the crank arm W2 intersects to perform profiling processing, thereby forming an annular groove W3 having a concave curve in cross section at the corner. .

As shown in FIG. 24, half of the outer peripheral surface of the journal portion W1 and the inner surface of one of the crank arms W2 are finished when viewed from the rotational direction of the crankshaft W, and the annular groove portion W3 is formed. The cutting insert and the indexable cutting tool are retracted from between the crank arm W2.

Next, by using a left-hand indexable cutting tool mirror-symmetrical with respect to a plane parallel to one side surface 11a of the tool body 11, the remaining half of the outer peripheral surface of the journal portion W1 and the other half of the outer peripheral surface of the journal portion W1 viewed from the rotational direction of the crankshaft W are cut. The inner surface of the crank arm W2 is finished, and an annular groove W3 is formed at the corner between the outer peripheral surface of the journal portion W1 and the inner surface of the crank arm W2.

Here, in the cutting insert and the indexable cutting tool configured as described above, the clamp screw 13 is inserted into the mounting hole 5 opening in the quadrangular surface 2 having the side flank 2a of the insert body 1 and the clamp screw 13 is inserted into the insert mounting seat 12 at the second end. 1 and is mounted by being screwed into a screw hole 12d formed in a wall surface 12b of 1, and an upper jaw-like part and a first side surface 3 directed in the rotation direction of the work material (crankshaft W) as a rake surface. The fixing screws are not arranged so as to overlap.

Therefore, chips generated by the cutting edge 6 during the finishing of the journal portion W1 and the crank arm W2 and the formation of the annular groove portion W3 do not get entangled in the upper jaw portion and the fixing screw. In the form, the chip breaker 3a rides on the flat surface 3b and is divided, and is smoothly discharged from between the crank arms W2. Therefore, even if the journal portion W1 becomes narrow due to downsizing of the engine, the finished journal portion W1 and the crank arm W2 will not be damaged, and the tool body 11 will not be damaged. Stable cutting can be performed.

In addition, in the cutting insert having the above configuration, the insert body 1 has a 180° rotational symmetry shape with respect to the center line O of the mounting hole 5, and has a shape that is inverted symmetrically with respect to the two quadrangular surfaces 2, and is used as a rake surface 2. Since the two first side surfaces 3 are parallelogram-shaped, one of the two acute-angled corner portions C of the first side surface 3, which is the rake face, is positioned so that the corner edge 6a of the cutting edge 6 is the insert mounting seat 12. When attached so as to be located on the opposite side of the first wall surface 12b, the other acute-angled corner portion C on the opposite side of this one acute-angled corner portion C is such that the corner edge 6a is attached to the first wall surface. 12b side.

Since the insert body 1 is pulled in by the clamp screw 13 in the direction in which the bottom surface 12a of the insert mounting seat 12 intersects the second wall surface 12c, as described above, the first wall surface 12c of the insert mounting seat 12 is mounted. One square surface 2 in contact with the wall surface 12b and the front flank surface 4a connected to the other acute corner portion C of the second side surface 4 in contact with the second wall surface 12c are the first, It is attached so as to be pressed against the second wall surfaces 12b and 12c. Therefore, since the insert body 1 can be attached to the insert mounting seat 12 like a wedge, it is possible to secure the mounting strength to the tool body 11 and perform stable cutting.

Furthermore, in the cutting insert configured as described above, the second side surface 4 is provided with two convex portions 7 that are connected to the acute-angled corner portions C of the two first side surfaces 3, respectively. Each has a step surface 7a facing the obtuse corner portion D of the first side surface 3 in the direction along the intersection ridgeline between the second side surface 4 and the quadrangular surface 2 . On the other hand, in the insert mounting seat 12 of the tool body 11 of the indexable cutting tool, the bottom surface 12a of the second side surface 4 of the insert body 1 is provided between the second wall surface 12c and the bottom surface 12a. A concave portion 12f is formed in which the convex portion 7 on the side of the first side surface 3 that abuts on is accommodated.

Therefore, if a cutting load acting on the cutting edge 6 used for cutting causes a force to rotate the insert body 1 around the center line O of the mounting hole 5, the clamp screw 13 should be loosened. Also, by engaging the projection 7 accommodated in the recess 12f with the recess 12f, it is possible to prevent the insert body 1 from falling off from the insert mounting seat 12. As shown in FIG. Therefore, it is possible to prevent the cutting insert, the tool body 11, or the crankshaft W, which is the work material, from being damaged due to the falling off of the insert body 1 as described above.

The stepped surface 7a of the convex portion 7 is a second portion that is continuous with the obtuse corner portion D of the first side surface 3 when viewed from the direction of the center line O of the mounting hole 5 as in the present embodiment. It is desirable to extend in a direction intersecting the intersection ridgeline L between the front flank 4a of the side surface 4 and the quadrangular surface 2 at an angle θ in the range of 90° to 135°.

If the angle θ is less than 90°, the step surface 7a protrudes outward from the insert body 1 toward the obtuse corner D of one of the two first side surfaces 3. As shown in FIG. 1, the convex portion 7 is likely to be chipped. Further, when the angle θ is an obtuse angle larger than 135°, the convex portion 7 is engaged with the concave portion 12f when a force acts to rotate the insert body 1 around the center line O of the mounting hole 5 as described above. There is a possibility that the effect of preventing falling off cannot be expected.

Although this angle θ is an obtuse angle in the above-described embodiment, the step surface 7a of the projection 7 is aligned with the intersecting ridgeline L as in the cutting insert of the modification of the above-described embodiment shown in FIGS. The angle ? 25 to 29, portions common to the embodiment shown in FIGS. 1 to 5 are assigned the same reference numerals.

In the above-described embodiment, flat surfaces 3 b perpendicular to the quadrangular surface 2 are formed on the two first side surfaces 3 so as to protrude outward from the insert body 1 beyond the cutting edge 6 . Therefore, when the first side surface 3 abuts against the bottom surface 12a of the insert mounting seat 12, the flat surface 3b abuts, preventing interference between the cutting edge 6 and the bottom surface 12a. The main body 1 can be brought into contact stably and the mounting strength can be further improved.

REFERENCE SIGNS LIST 1 insert body 2 quadrangular surface 3 first side surface 3a chip breaker 3b flat surface 4 second side surface 5 mounting hole 6 cutting edge 6a corner edge 6b end cutting edge 6c transverse edge 7 convex portion 7a stepped surface 11 tool body 11a tool One side surface of body 11 12 Insert mounting seat 12a Bottom surface of insert mounting seat 12 12b First wall surface of insert mounting seat 12 12c Second wall surface of insert mounting seat 12 12d Screw hole 12f Recess 13 Clamp screw C First side surface Acute-angled corner portion of 3 D Obtuse-angled corner portion of first side surface 3 O Center line of mounting hole 5 L Intersecting ridgeline between quadrangular surface 2 and second side surface 4 θ Viewed from center line O direction of mounting hole 5 Angle formed by stepped surface 7a with respect to intersecting ridgeline L W Crankshaft (work material)
W1 Journal part W2 Crank arm

Claims (3)

A square plate-shaped insert body is provided, and a mounting hole passing through the insert body is opened in the center of two square faces of the insert body, and the insert body is oriented 180° with respect to the center line of the mounting hole. It has a rotationally symmetrical shape and a symmetrical shape with the front and back inverted with respect to the two quadrangular surfaces,
The four sides of the insert body arranged around the two square faces are two first sides facing away from each other and two second sides located between the two first sides. having a side and
The two first side surfaces are parallelogram-shaped when viewed from the direction facing the first side surfaces, and each of the first side surfaces is a rake surface. A cutting edge having a corner edge is formed at the sharp corner of the rake face,
The corner edges of these cutting edges are arranged at diagonal positions of the two quadrilateral surfaces and diagonal positions of the two second side surfaces,
The second side surface is provided with convex portions at two locations connected to the acute-angled corner portions of the two first side surfaces,
When viewed from the direction facing the second side surface, each of the two protrusions is located in the direction along the intersection ridgeline between the second side surface and the quadrilateral surface . having a stepped surface facing an obtuse-angled corner portion of the first side surface facing away from the first side surface on which the convex portions are arranged ;
A cutting insert, wherein the two first side surfaces serving as the rake surfaces are formed with flat surfaces that are perpendicular to the quadrangular surface and protrude outward from the insert body beyond the cutting edge. . The stepped surface has an angle of 90° to 135° with respect to an intersection ridge line between the second side surface and the quadrangular surface, which is continuous with the obtuse angle corner portion of the first side surface, when viewed from the center line direction of the mounting hole. The cutting insert according to claim 1, characterized in that it extends in the transverse direction at a range of angles. A recessed insert mounting seat is formed at the tip of the plate-shaped tool body, and the cutting insert is inserted through the mounting hole of the cutting insert into the insert mounting seat. An indexable cutting tool detachably attached by a clamp screw screwed into a mounting seat,
The above cutting insert is
The insert body is provided with a rectangular plate shape, and the mounting hole passing through the insert body is opened in the center of the two rectangular faces of the insert body, and the insert body is 180 with respect to the center line of the mounting hole. ° It has a rotationally symmetrical shape and a symmetrical shape with the front and back inverted with respect to the two quadrangular surfaces,
The four sides of the insert body arranged around the two square faces are two first sides facing away from each other and two second sides located between the two first sides. having a side and
The two first side surfaces are parallelogram-shaped when viewed from the direction facing the first side surfaces, and each of the first side surfaces is a rake surface. A cutting edge having a corner edge is formed at the sharp corner of the rake face,
The corner edges of these cutting edges are arranged at diagonal positions of the two quadrilateral surfaces and diagonal positions of the two second side surfaces,
The second side surface is provided with convex portions at two locations connected to the acute-angled corner portions of the two first side surfaces,
When viewed from the direction facing the second side surface, each of the two protrusions is located in the direction along the intersection ridgeline between the second side surface and the quadrilateral surface. having a stepped surface facing an obtuse-angled corner portion of the first side surface facing away from the first side surface on which the convex portions are arranged;
The insert mounting seat has a bottom surface with which one of the two first side surfaces of the insert body abuts, and a first square surface with which one of the two square surfaces of the insert body abuts. 1 wall surface and a first side surface of the two second side surfaces of the insert body opposite to the one first side surface abutting the bottom surface of the insert body, which is connected to an acute-angled corner portion of the rake surface. a second wall surface facing the tip side of the tool body with which the portion abuts,
The second wall surface is inclined toward the first wall surface toward the rear end of the tool body, and the first wall surface is provided with a screw hole into which the clamp screw is screwed. ,
Between the bottom surface and the second wall surface, one of the two second side surfaces of the insert body is directed toward the rear end of the tool body and brought into contact with the second wall surface. a concave portion is formed in which the convex portion on the one first side surface that is brought into contact with the bottom surface of the second side surface is accommodated,
The insert body is attached by being drawn in by the clamp screw in a direction in which the bottom surface and the second wall surface of the insert attachment seat intersect when viewed from the direction facing the first wall surface. indexable cutting tool.

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