Cutting insert, cutting tool, and method of manufacturing machined product

In an embodiment, a cutting insert includes a body member and a cutting member. The body member is a columnar body, and includes: an upper surface; a lower surface; and an outer side surface between the upper surface and the lower surface. The cutting member is located at a corner part of the outer side surface in the body member. The cutting member includes: at least three surfaces being exposed; and a cutting edge at an intersecting portion of two of the at least three surfaces. The body member includes a through hole penetrating through the upper surface and the lower surface.

TECHNICAL FIELD

The present embodiments relate to a cutting insert, a cutting tool, and a method of manufacturing a machined product.

BACKGROUND ART

As a cutting insert used when a workpiece, such as metal, is subjected to a milling process, an indexable insert described in Japanese Unexamined Patent Publication No. 2003-231015 (Patent Document 1) has been known. The indexable insert described in Patent Document 1 is made up of an indexable insert body (body member) composed of a sintered body, such as cemented carbide or ceramics, and a diamond insert (cutting edge member). A recessed part is disposed at an intersecting portion of a side flank surface and a front flank surface on a rake surface of the indexable insert body, and an insert is brazed to the recessed part.

The diamond insert is provided with an outer side cutting edge and a bottom cutting edge, namely, the outer side cutting edge and the bottom cutting edge are made of diamond, thereby enhancing the strength of a cutting edge. A through hole extends from a rake surface located at the front in a rotation direction to a surface located at the rear in the rotation direction in the indexable insert. The indexable insert is configured to be attached to a rotary cutting tool body (holder) by inserting a clamp screw member into the through hole.

In the configuration that the cutting edge member is connected to the recessed part in the body member as is the case with the cutting insert described in Patent Document 1, a region with a small thickness is formed between the recessed part and the through hole. Durability can become insufficient in the region with the small thickness, for example, when the cutting insert is miniaturized.

The present embodiments are intended to provide a cutting insert having good durability when the cutting insert is made up of a body member and a cutting edge member.

SUMMARY

In an embodiment, a cutting insert includes: a body member and a cutting member. The body member is a columnar body, and includes: an upper surface; a lower surface; and an outer side surface between the upper surface and the lower surface. The cutting member is located at a corner part of the outer side surface of the body member. The cutting member includes: at least three surfaces being exposed; and a cutting edge at an intersecting portion of two of the at least three surfaces. The body member further includes a through hole penetrating through the upper surface and the lower surface.

EMBODIMENTS

A cutting insert and a cutting tool according to an embodiment are described in detail below with reference to the drawings. For convenience of description, the drawings referred to in the following show, in simplified form, only major components among components of the embodiments. Therefore, the cutting insert and the cutting tool of the present invention may include any optional component not shown in the drawings referred to in the present description. Sizes of the components in the drawings are not faithful to sizes of actual components and to size ratios of these individual components.

In the present embodiment shown inFIGS. 1 to 5, the cutting tool101of the present embodiment includes a holder103, a plurality of cutting inserts1(hereinafter also referred to as “inserts1”), and a screw105.

The holder103has a rotation axis O1. A side where the inserts1are located is referred to as a front end side, and the opposite of the front end side is referred to as a rear end side, the holder103is a columnar body member extending along the rotation axis O1from the front end side toward the rear end side. The holder103rotates in a rotation direction X1around the rotation axis O1about the rotation axis O1during a cutting process of a workpiece for manufacturing a machined product. In the present embodiment, a central axis of the holder103that is the columnar body and the rotation axis O1of the holder103coincide with each other.

Hereinafter, a side close to the rotation axis O1is referred to as an inner peripheral side, and a side away from the rotation axis O1is referred to as an outer peripheral side. A direction from the rear end side of the holder103toward the front end side thereof is referred to as a front end direction, and a direction from the front end side of the holder103to the rear end side thereof is referred to as a rear end direction.

For example, steel, cast iron, or aluminum alloy is usable for the holder103. In the present embodiment, steel having high toughness among these materials is used for the cutting tool101. The size of the holder103is suitably settable according to the size of a workpiece. For example, a length in the direction along the rotation axis O1is settable to approximately 30-90 mm. A width (diameter) in a direction orthogonal to the rotation axis O1is settable to approximately 20-500 mm.

A plurality of insert pockets107(hereinafter also referred to as “pockets107”) are located along an outer peripheral side on the front end side of the holder103. The pockets107, to which the inserts1are respectively attached, open into the outer peripheral side on the front end side of the holder103before the attachment of the inserts1. The pockets107may be disposed at equal intervals or unequal intervals so as to have rotational symmetry around the rotation axis O1. The pockets107are preferably disposed at equal intervals in order to reduce variations in load applied to the inserts1attached to the pockets107.

The pockets107are located on the holder103, and therefore the holder103is not a strict columnar body. Each of the inserts1attached to the pockets107is fixed to the holder103by the screw105.

In the present embodiment illustrated inFIG. 4, exemplary eight pockets107are disposed on the holder103and the inserts are respectively located at these eight pockets107. The number of the pockets107, and the number of the inserts1attached to the holder103are not limited to eight. Therefore, both numbers may be, for example, two, three, four, five, six, or ten or more.

In the present embodiment illustrated inFIGS. 6 to 10, each of the inserts1is made up of the body member3and the cutting member5, and has a columnar body as a whole. In the instant embodiment, the body member3is a columnar body, and the body member3is a quadrangular columnar body. The body member3includes an upper surface7, a lower surface9, and an outer side surface11. The outer side surface11is located between the upper surface7and the lower surface9.

The cutting member5is located at a corner part of the outer side surface11of the body member3. In other words, the cutting member5is located at a recessed part13included in the corner part of the outer side surface11of the body member3. In the present embodiment, each of the inserts1are therefore the columnar body as a whole.

The cutting member5is fixed to the body member3. The cutting member5is connected to the body member3by using a brazing filler metal or the like in the present embodiment. In order to facilitate visual understanding, hatching made up of diagonal lines is applied to the cutting member5inFIGS. 6 to 10.

The cutting member5is a part of the insert1and includes a cutting edge15for cutting a workpiece. Also, the cutting member5has high hardness to ensure the high strength cutting edge15in the insert1. Thus, the cutting edge15is not located on the body member3but located on the cutting member5in the present embodiment. The body member3is a base part in the insert1and need not have hardness equal to or higher than that of the cutting member3. Manufacturing costs for the inserts1are reducible while enhancing the strength of the cutting edges15because the inserts1are thus respectively made up of the body member3and the cutting member5.

For example, cemented carbide or cermet is usable as a material of a member constituting the body member3. Examples of compositions of the cemented carbide include WC—Co, WC—TiC—Co, and WC—TiC—TaC—Co. WC—Co is producible by adding cobalt (Co) powder to tungsten carbide (WC), followed by sintering. For WC—TiC—Co, titanium carbide (TiC) is added to WC—Co. For WC—TiC—TaC—Co, tantalum carbide (TaC) is added to WC—TiC—Co.

The cermet is a sintered composite material obtainable by compositing the metal with a ceramic ingredient. Specific examples of the cermet include those containing a titanium compound as a main component such as titanium carbide (TiC) or titanium nitride (TiN).

The cutting member5is made of a material having a higher hardness than a material constituting the body member3. Specifically, examples of the material of the cutting member5include polycrystalline diamond and monocrystalline diamond. The hardness of the body member3and the cutting member5is evaluable by measuring Vickers hardness of their respective parts.

For Vickers hardness measurement, a well-known test method can be used. In the method, for example, a pyramid-shaped indenter made of a square pyramid diamond is pressed against the surface of a material, and then measured is an indent that remains after removing a load. When the indenter is pressed against the body member3, an indent is formed on the body member3because the material of the body member3is made of the material having a lower hardness than the indenter as illustrated above. When the material of the cutting member5is monocrystalline diamond, little or no indent is formed.

In the present embodiment, the upper surface7and the lower surface9of the body member3have a tetragonal shape. The upper surface7is a surface that comes into contact with a seating surface of the pocket107of the holder103when the insert1is attached to the holder103. The lower surface9is a surface being exposed to the front end side of the holder103when the insert1is attached to the holder103.

The outer side surface11of the body member3includes four surface regions of a front side surface17, a rear side surface19, an outer side surface21, and an inner side surface23. The side surfaces17,19,21and23are respectively correspond to sides of the upper surface7and the lower surface9each having the tetragonal shape (where the side surfaces are named not only fromFIG. 6but also from a positional relationship under a situation of the base member3attached to the holder103). These surface regions have an approximately tetragonal shape in their respective front views.

The front side surface17is a surface region located at the front in the rotation direction X1when the insert1is attached to the holder103. In the front view of the front side surface17, its width in a direction orthogonal to the rotation axis O1is larger than its height in a direction along the rotation axis O1. The rear side surface19is another surface region located at the rear in the rotation direction X1when the insert1is attached to the holder103. The rear side surface19is located opposite to the front side surface17, and comes into contact with the pocket107when the insert1is attached to the holder103.

The outer side surface21is another surface region of the outer side surface1which is located closest to the outer peripheral side when the insert1is attached to the holder103. The outer side surface21protrudes from the holder103in an outer side direction. Although the entirety of the outer side surface21protrudes from the holder103in the present embodiment, there is no intention to limit to this configuration. For example, a part of the outer side surface21which is close to the front side surface17may partially protrude from the holder103in the outer side direction.

The inner side surface23is another surface region located close to the inner peripheral side when the insert1is attached to the holder103, and comes into contact with the pocket107when the insert1is attached to the holder103.

The description that the upper surface7, the lower surface9, the front side surface17, the rear side surface19, the outer side surface21, and the inner side surface23have the tetragonal shape denotes that these surfaces need to have an approximately tetragonal shape but need not to have a strict tetragonal shape. Corners of the surface regions may have a round shape in their respective front views. Also, sides located so as to connect adjacent corners need not to have a strict straight line, but may be partially made into a shape having concave and convex.

The size of the body member3is not particularly limited. In the present embodiment, for example, a maximum value of a width between the front side surface17and the rear side surface19can be set to approximately 5-20 mm in a top view (in a front view of the upper surface3). A maximum value of a width between the inner side surface23and the outer side surface21can be set to approximately 5-20 mm in the top view. A maximum value of a thickness between the upper surface7and the lower surface9is 3-10 mm.

In the present embodiment, the body member3includes the recessed part13. The recessed part13is located at a part thereof which corresponds to a region of the front side surface17on the outer side surface11which is close to the outer side surface21, corresponds to a region of the outer side surface21which is close to the front side surface17, and corresponds to a corner of the lower surface9. It can also be said that the recessed part13in the present embodiment is located at a part of a corner of the upper surface7and a part of the corner of the lower surface9, besides on the outer side surface11.

The cutting member5is located at the recessed part13of the body member3. The cutting members includes at least three surfaces that are exposed. In the present embodiment, the cutting member5has a tetragonal plate shape, and includes a first surface25located close to the front side surface17of the body member3that is exposed. The cutting member5also include a second surface27located close to the outer side surface21of the body member3, and a third surface29located close to the lower surface9of the body member3that are exposed.

The cutting member5includes the cutting edge15on an intersecting portion where two of the exposed surfaces intersect each other. The cutting edge15includes a first cutting edge15A and a second cutting edge15B in the present embodiment. The first cutting edge15A is located at an intersecting portion of the cutting member5where the first surface25and the second surface27intersect each other. Accordingly, the first cutting edge15A extends in a direction from the upper surface7toward the lower surface9of the body member3in the present embodiment.

In the present embodiment, the cutting tool101is a tool for use in a so-called milling process for cutting a workpiece by causing the holder103to move in the direction approximately orthogonal to the rotation axis O1while the holder103is rotating around the rotation axis O1. The first cutting edge15A therefore functions as a so-called outer side cutting edge configured to mainly cut the workpiece.

The first cutting edge15A is located over the entirety of the intersecting portion of the first surface25and the second surface27in the present embodiment. Although the first cutting edge15A may be located at least on a part of the intersecting portion of the first surface25and the second surface27. The first cutting edge15A is disposed over the entirety of the intersecting portion of the first surface25and the second surface27in order to ensure a large height of cut in the present embodiment. The length of the first cutting edge15A can be set to, for example, approximately 3-7 mm.

The first cutting edge15A protrudes outward from the outer side surface11of the holder103when the insert1is attached to the holder103. The first cutting edge15A has such a straight line form that is inclined so as to approach the rear side surface19as going from an end portion of the first cutting edge15A which is close to the lower surface9toward an end portion of the first cutting edge15A which is close to the upper surface7. An axial rake θ of the first cutting edge15A can be set to, for example, approximately 3-10° when the insert1is attached to the holder103, a.

When the first cutting edge15A is so located, it is possible to decrease the likelihood that the body member3can come into contact with a workpiece during a cutting process of the workpiece.

The second cutting edge15B is located on an intersecting portion of the first surface25and the third surface29in the cutting member5. Therefore, the second cutting edge15B in the present embodiment extends in a direction along the lower surface9of the body member3.

In the present embodiment, the second cutting edge15B functions as a “flat cutting edge” to decrease unevenness on a machined surface of the workpiece. Hence, the second cutting edge15B need not necessarily be disposed over the entirety of the intersecting portion of the first surface25and the third surface29, but is preferably disposed so as to include a part of the second cutting edge15B which is located close to the outer periphery in a state of being attached to the holder103(which is namely a right side of the second cutting edge15B inFIG. 9). The length of the second cutting edge15B can be set to, for example, approximately 2-5 mm.

The second cutting edge15B protrudes toward the front end side of the holder103when the insert1is attached to the holder103. The second cutting edge15B has a downwardly convex shape when viewed from the front in the rotation direction X1(for example, inFIG. 9). When the second cutting edge15B is so located, it is possible to minimize the likelihood that the body member3can come into contact with the workpiece during the cutting process of the workpiece.

The second cutting edge15B includes a straight line portion. In the present embodiment, the straight line portion extends from the outer peripheral side in the state of being attached to the holder103(i.e., the right side of the second cutting edge15B inFIG. 9) toward an inner peripheral side. With the second cutting edge15B that includes the straight line portion, the second cutting edge15B can function well as the flat cutting edge. A radial rake of the second cutting edge15B can be set to, for example, approximately 5-20° when the insert1is attached to the holder103.

If the second cutting edge15B protrudes as describe above, it is possible to avoid that the body member3comes into contact with the workpiece without inclining the holder103more than necessary.

In the present embodiment, the body member3of the insert1includes a through hole31. The through hole31is a portion through which the insert1is screwed to the holder103. Specifically, the screw105is inserted into the through hole31of the insert1, a front end of the screw105is inserted into a screw hole (not shown) that is formed in the pocket107and therefore the screw105is fixed to the screw hole. Accordingly, the insert1is attached to the holder103.

The through hole31penetrates through the center of the upper surface7and the center of the lower surface9of the main body3. In other words, the through hole31is located from the center of the upper surface7to the center of the lower surface9of the body member3, and opens into the center of the upper surface7and the center of the lower surface9. Therefore, the through hole31does not open into the outer side surface11of the main body3. In the presentembodiment, a penetrating direction of the through hole31extends along the rotation axis O1.

If the through hole31penetrates through the front side surface17and the rear side surface19, or if the through hole31penetrates through the outer side surface21and the inner side surface23, provided that the through hole31is identical in size, a small thickness region is formed between the recessed part13and the through hole31of the body member3. If the small thickness region exists, the small thickness region can be damaged due to a load applied to the insert1during the cutting process.

However, in the present embodiment, because the through hole31penetrates through the lower surface9and the upper surface7, the recessed part13and the through hole31are located away from each other. In other words, the first cutting edge15A subjected to a large cutting resistance and the through hole31are located away from each other. Therefore, a formation of the small thickness region between the recessed part13and the through hole31can be avoided. This leads to the insert1having good durability.

If the through hole31is formed from the front side surface17to the rear side surface19, it follows that the head of the screw105is located ahead of a chip flow, and hence the head of the screw105can be damaged. In contrast, in the present embodiment, the through hole31opens into the upper surface7and the lower surface9in the present embodiment, and therefore, the likelihood of damage to the head of the screw105can be reduced.

The first surface25of the cutting member5is located at the front in the rotation direction X1. Therefore, the first surface25in the cutting member5functions as “a rake surface” along which chips flow during the cutting process. Hereinafter, the first surface25is therefore also referred to as the rake surface. The second surface27and the third surface29in the cutting member5function as “a flank surface” during the cutting process.

In the present embodiment shown inFIG. 8, the entirety of the second cutting edge15B is located closer to the outer peripheral side than the through hole31. Specifically, the entirety of the second cutting edge15B is located closer to the outer peripheral side than a middle part of the through hole31whose inner diameter is constant. A load due to a principal force is applied from the second cutting edge15B toward the rear in the rotation direction X1during the cutting process.

However, because the second cutting edge15B is located closer to the outer peripheral side than the through hole31, direct transmit of the load from the second cutting edge15B toward the through hole31can be avoided. As a result, the durability of the insert1is further enhanced. The phrase “being located closer to the outer peripheral side” denotes being located away from the rotation axis O1of the holder103.

In the present embodiment as shown inFIG. 9, for example, a vertical thickness of the body member3in the corner part where the cutting member5is located is larger than a vertical thickness thereof in a part other than the corner part. Hence, when attached to the holder103, a part of the body member3which is located on the outer peripheral side protrudes toward the front end side. In other words, the inner peripheral side of the body member3has a partially indented shape inFIG. 9.

This ensures that the length of the first cutting edge15A is made longer. It is preferably possible to stably reduce the likelihood that the body member3and the holder103come into contact with the workpiece during a ramping process in which the holder103moves in a direction slightly inclined toward the front end side from the direction approximately orthogonal to the rotation axis O1while rotating around the rotation axis O1.

A ridge line where the outer side surface21and the lower surface9intersect each other is inclined so as to be located closer to the front end side as going toward the front in the rotation direction X1, and he second cutting edge15B protrudes most toward the front end direction, when the insert1is viewed from the side as shown inFIG. 10. This makes it possible to reduce the likelihood that the lower surface9comes into contact with the workpiece.

It is also possible to reduce the likelihood that the lower surface9comes into contact with the workpiece even when the outer side surface21in the body member3has the following configuration. That is, a part of the outer side surface21which is located close to the front in the rotation direction X1protrudes toward the front end side when attached to the holder103. In other words, in the present embodiment, a part of the ridge line where the outer side surface21and the lower surface9intersect each other, which is located close to the front in the rotation direction X1protrudes toward the front end side.

In the present embodiment, the insert1has a parallelogram shape in which an angle formed by the front side surface17and the outer side surface21is an acute angle when the insert1is viewed from above. This ensures a large distance between the first cutting edge15A and the through hole31, thereby making it easier to ensure a large thickness between a concave shaped portion to which the cutting member5in the body member3is connected, and the through hole31. It is therefore possible to further enhance the durability of the insert1.

In the present embodiment, the entirety of the cutting edge15is located at the front in the rotation direction relative to the through hole31. A load is also applied from the cutting edge15toward the rotation axis O1during the cutting process. However, when the entirety of the cutting edge15is located at the front in the rotation direction relative to the through hole31, it is possible to avoid that the load is directly transmitted from the cutting edge15toward the through hole31. Consequently, the insert1can have enhanced durability.

While the cutting tool101and the insert1according to the embodiment have been described in detail with reference to the drawings, the cutting tool and the cutting insert according to the present invention are not limited to the configurations in the above embodiment.

A method of manufacturing a machined product according to an embodiment is described below with reference to the drawings.

The machined product is manufacturable by subjecting a workpiece201to a cutting process. The method of manufacturing the machined product in the present embodiment includes the following steps:

(1) rotating the cutting tool101represented by the above embodiment around the rotation axis O1;

(2) bringing the cutting edge15in the cutting tool101being rotated into contact with the workpiece201; and

(3) separating the cutting tool101from the workpiece201.

More specifically, firstly, the cutting tool101is relatively brought near the workpiece201by rotating the cutting tool101around the rotation axis O1and moving the cutting tool101in X2direction as shown inFIG. 11. Subsequently, the workpiece201is cut by bringing the cutting edge15in the cutting tool101into contact with the workpiece201. As the cutting edge15, the first cutting edge and the second cutting edge are brought into contact with the workpiece201in the present embodiment as shown inFIG. 12. Thereafter, the cutting tool101is relatively separated from the workpiece201by further moving the cutting tool101in the X2direction as shown inFIG. 13.

In the present embodiment, the cutting tool101is brought near the workpiece201in a state in which the workpiece201is fixed and the cutting tool101is rotated around the rotation axis O1. InFIG. 12, the workpiece201is cut by bringing the first cutting edge and the second cutting edge of the insert1being rotated into contact with the workpiece201. InFIG. 13, the cutting tool101being rotated is separated from the workpiece201.

In the present embodiment, during the cutting process with the manufacturing method, the cutting tool101is brought into contact with the workpiece201, or the cutting tool101is separated from the workpiece201by moving the cutting tool101in each of the above steps. Nevertheless, there is no intention to limit to such embodiments.

For example, in the step (1), the workpiece201may be brought near the cutting tool101. Similarly, in the step (3), the workpiece201may be separated from the cutting tool101. When the cutting process is continued, it is necessary to repeat the step of bringing the cutting edge15in the insert1into contact with different portions of the workpiece201while keeping the cutting tool101rotated.

Representative examples of the material of the workpiece201include aluminum, carbon steel, alloy steel, stainless steel, cast iron, and nonferrous metals.

DESCRIPTION OF THE REFERENCE NUMERAL