WO2024224817A1 - Cutting tool and method for manufacturing machined product - Google Patents

Abstract

There is a need for a cutting tool that has a configuration in which chips can be easily removed during insert replacement work. A cutting tool based on one aspect of the present disclosure has: a holder that has a pocket; an insert that is attached to the holder; and a fixing screw that fixes the insert to the holder. The fixing screw has a shaft and a head. The head has a hexalobular hole and a slit that extends from one lobe of the hexalobular hole to the outer edge of the head.

Description

Cutting tool and method for manufacturing machined product

The present disclosure relates to a cutting tool and a method for manufacturing a machined product. Examples of cutting tools include rotary tools and turning tools. Examples of rotary tools include milling tools. Turning tools can be used for milling processes such as face milling and end milling. Examples of turning tools include external diameter machining tools, internal diameter machining tools, grooving tools, and cut-off tools.

In cutting tools in which an insert is attached to a holder by a fixing screw, the insert is replaced when it becomes worn. When replacing the insert, it is necessary to remove the chips that have entered the screwdriver hole in the head of the fixing screw. The insert replacement method described in Patent Document 1 is known as a process for removing the chips. In Patent Document 1, the chips are removed by blowing air into the screwdriver hole.

Japan "JP Patent Publication No. 2021-154434"

A cutting tool according to one aspect of the present disclosure includes a holder having a pocket, an insert attached to the holder, and a fixing screw for fixing the insert to the holder. The fixing screw has a shaft and a head, and the head has a hexlobe hole and a slit extending from a corner of the hexlobe hole to the outer edge of the head.

FIG. 1 is a perspective view of a cutting tool according to an embodiment of the present disclosure. FIG. 2 is an enlarged view of region II shown in FIG. 3 is a cross-sectional view taken along line III-III of the cutting tool shown in FIG. 2. FIG. 2 is a perspective view of an insert in the cutting tool shown in FIG. 1 . FIG. 2 is a perspective view of a fixing screw in the cutting tool shown in FIG. 1 . FIG. 6 is a plan view of the fixing screw shown in FIG. 5 . FIG. 6 is a plan view of a first modified example of the fixing screw shown in FIG. 5 . 8 is a cross-sectional view taken along line VIII-VIII of the fixing screw shown in FIG. 6. 5. FIG. 9 is a cross-sectional view corresponding to FIG. 8 in a second modified example of the fixing screw shown in FIG 7 is a cross-sectional view taken along line XX of the fixing screw shown in FIG. 6. 10 in a third modified example of the fixing screw shown in FIG. 5. FIG. 3 is a schematic diagram showing one step of a manufacturing method of a machined product according to an embodiment. FIG. 3 is a schematic diagram showing one step of a manufacturing method of a machined product according to an embodiment. FIG. 3 is a schematic diagram showing one step of a manufacturing method of a machined product according to an embodiment. FIG.

The hole for turning the fixing screw in a cutting tool is generally a hexalobular hole (a hole shaped like a six-pointed star). As a result, chips tend to remain in the six corners of the hexalobular hole, and there is a risk that the chips may not be sufficiently removed even by blowing air. For this reason, there is a demand for cutting tools that are designed to make it easy to remove chips when replacing inserts.

The cutting tool 1 according to the embodiment of the present disclosure and the method for manufacturing a machined product will be described in detail below with reference to the drawings. However, for the sake of convenience, each of the drawings referred to below shows a simplified version of only the components necessary to explain the embodiment. Therefore, the cutting tool 1 according to the embodiment of the present disclosure may include any components not shown in each of the drawings referred to. Furthermore, the dimensions of the components in each drawing do not faithfully represent the actual dimensions of the components and the dimensional ratios of each member, etc.

<Cutting tools>
1, a cutting tool 1 according to an example of the present disclosure is a rotary tool used for turning. In addition to rotary tools, the cutting tool 1 may also be a tool used for turning such as external diameter machining, internal diameter machining, and grooving.

The cutting tool 1 may have a holder 3, an insert 5, and a fixing screw 7. The holder 3 has a columnar shape extending from a first end 3a to a second end 3b along a rotation axis O1. In FIG. 1 and other figures, the direction of rotation about the rotation axis O1 is indicated by Y1. If the cutting tool 1 is a tool used for turning as described above, the rotation axis O1 may be replaced with the central axis.

The cutting tool 1 may have a pocket 9 located on the side of the first end 3a. There may be only one pocket 9, or there may be multiple pockets 9 as in the example shown in FIG. 1. As in the example shown in FIG. 1, the multiple pockets 9 may each open to the outer circumferential surface of the holder 3 and the end face on the side of the first end 3a. When the cutting tool 1 is viewed from the front from the side of the first end 3a, the multiple pockets 9 may be arranged at equal or unequal intervals.

The pocket 9 is a space in which the insert 5 and the fixing screw 7 are positioned. The pocket 9 may also be used as a space through which chips generated during cutting to manufacture a machined product can flow.

The holder 3 can be made of steel, cast iron, or the like. For example, from the viewpoint of increasing the toughness of the holder 3, steel may be used among these materials.

The insert 5 is located in the pocket 9 and attached to the holder 3. The example insert 5 shown in FIG. 4 has a polygonal plate shape and has an upper surface 11, a lower surface 13, side surfaces 15, and a through hole 17.

The upper surface 11 of the insert 5 may be polygonal and may be located relatively forward in the rotational direction Y1 of the insert 5 when the insert 1 is attached to the holder 3, as in the example shown in FIG. 1. The upper surface 11 may be rotationally symmetrical by 180° with respect to the center of the upper surface 11, as in the example shown in FIG. 4. The center of the upper surface 11 can be identified, for example, by the intersection of the diagonals of the upper surface 11. The lower surface 13 may be located on the opposite side of the upper surface 11, and may be located relatively backward in the rotational direction Y1 of the insert 5 when the insert 1 is attached to the holder 3, as in the example shown in FIG. 1.

The side surface 15 of the insert 5 may be located between the upper surface 11 and the lower surface 13. The side surface 15 may be connected to each of the upper surface 11 and the lower surface 13. In the example shown in FIG. 4, since the upper surface 11 is polygonal, the side surface 15 has flat surface areas located along the edges of the upper surface 11 and convex surface areas located along the corners of the upper surface 11.

The example insert 5 shown in FIG. 4 has a generally rectangular plate shape, with the upper surface 11 and the lower surface 13 each being rectangular. When the upper surface 11 and the lower surface 13 have the above configuration, the side surface 15 has four flat surface areas and four convex surface areas. The shape of the insert 5 is not limited to the above configuration. For example, the upper surface 11 may not be rectangular, but may be, for example, generally triangular, generally pentagonal, or generally hexagonal.

The through hole 17 in the insert 5 extends from the upper surface 11 to the lower surface 13, and opens at the center of the upper surface 11 and the center of the lower surface 13. The through hole 17 is a portion for inserting (inserting) the fixing screw 7. The fixing screw 7 inserted into the through hole 17 is fixed in the pocket 9, thereby fixing the insert 5 to the holder 3.

The through hole 17 has a central portion 17a, a first conical portion 17b, and a second conical portion 17c. The central portion 17a is located in the center of the thickness direction of the insert 5 (direction from the upper surface 11 toward the lower surface 13) and has a constant inner diameter. The first conical portion 17b is located from the central portion 17a toward the upper surface 11, and has a truncated cone shape whose inner diameter increases with increasing distance from the central portion 17a. The second conical portion 17c is located from the central portion 17a toward the lower surface 13, and has a truncated cone shape whose inner diameter increases with increasing distance from the central portion 17a.

2 and 3, the pocket 9 in the holder 3 has a restraining seat 19 against which the lower surface 13 of the insert 5 abuts, and a restraining side surface 21 against which the side surface 15 of the insert 5 abuts. For example, the restraining seat 19 may be rectangular in shape corresponding to the lower surface 13, and the restraining side surface 21 may be composed of two flat surface areas corresponding to the two flat surface areas of the side surface 15. Also, as in the example shown in FIG. 3, the restraining seat 19 may be provided with a screw hole 23 into which the fixing screw 7 is screwed. The screw hole 23 includes the central axis of the through hole 17 in the insert 5 and extends in a direction along the central axis.

As shown in the example in FIG. 4, the insert 5 has an upper cutting edge 25 located at the intersection of the upper surface 11 and the side surface 15. The upper cutting edge 25 may be located over the entire intersection of the upper surface 11 and the side surface 15, or may be located over only a portion of this intersection. In addition to the upper cutting edge 25, the insert 5 may have a lower cutting edge 27 located at the intersection of the lower surface 13 and the side surface 15. The lower cutting edge 27 may be located over the entire intersection of the lower surface 13 and the side surface 15, or may be located over only a portion of this intersection.

In one cutting process, either the upper cutting edge 25 or the lower cutting edge 27 is used. For example, when the lower surface 13 of the insert 5 abuts against the restraining seat surface 19 of the pocket 9 (see FIG. 3), the upper cutting edge 25 is used for cutting. If the upper cutting edge 25 wears down to a predetermined amount or more, the insert 5 may be removed from the pocket 9, turned upside down (front and back), and then reattached to the pocket 9. In this case, the upper surface 11 of the insert 5 abuts against the restraining seat surface 19 of the pocket 9, and the lower cutting edge 27 can be used for cutting.

The fixing screw 7 is a member for fixing the insert 5 to the holder 3. The fixing screw 7 is inserted into the through hole 17 of the insert 5 and is screwed into the threaded hole 23 (see FIG. 3) formed in the restraining seat surface 19 of the pocket 9 in the holder 3.

<Fixing screw>
As shown in the example in Fig. 5, the fixing screw 7 has a head 29 and a shank 31. The shank 31 is a rod-shaped portion located at the tip end of the fixing screw 7, and has a screw groove 33 formed on its outer circumferential surface. The head 29 is located at the rear end of the fixing screw 7, and has a larger outer diameter than the shank 31. The head 29 is, for example, dish-shaped or round-dish-shaped. The surface of the head 29 located on the shank 31 side and that abuts against the insert 5 is the seat 43. That is, the insert 5 is sandwiched between the seat 43 of the fixing screw 7 and the restraining seat 19 of the pocket 9 (see Fig. 3).

A thread groove 33 is formed at least on the tip side of the shaft portion 31. The insert 5 is sandwiched between the head 29 of the fixing screw 7 and the restraining seat surface 19 of the pocket 9, and the thread groove 33 of the fixing screw 7 screws into the thread groove (not shown) of the screw hole 23, thereby fixing the insert 5 to the holder 3 (see FIG. 3).

A screwdriver hole is formed in the rear end face of the head 29. Specifically, a hexlobe hole 35 (a six-pointed star-shaped hole) is formed as the screwdriver hole. A hexlobe-shaped tool is inserted into the hexlobe hole 35, and the fixing screw 7 can be attached and detached by rotating the tool.

As shown in the example in FIG. 5, the head 29 of the fixing screw 7 has a hexlobe hole 35 and further has a slit 37 that extends from a corner of the hexlobe hole 35 to the outer edge of the head 29. The corners of the hexlobe hole 35 are the protruding corners of a star, and in the case of a hexagonal star, there are six corners. The slits 37 may extend from each of the multiple corners of the hexlobe hole 35, or may extend from one of the corners of the hexlobe hole 35, as in the example shown in FIG. 5.

When cutting is performed using the cutting tool 1, some of the chips generated during cutting may get into the hexlobe hole 35. Therefore, when using a hexlobe-shaped tool to attach or remove the fixing screw 7, it is necessary to remove the chips that have gotten into the hexlobe hole 35 beforehand. However, compared to a hex socket (hexagonal hole), which is a common hole for turning screws, it is difficult to remove the chips that have gotten into the hexlobe hole 35.

However, if the head 29 of the fixing screw 7 has the above-mentioned slit 37, the chips that have entered the hexlobe hole 35 can be discharged to the outside through this slit 37. Therefore, even if the head 29 of the fixing screw 7 has a hexlobe hole 35, the chips that have entered the hexlobe hole 35 can be stably removed.

When the slits 37 extend from each of the multiple corners of the hexalobular hole 35, chips that have entered the hexalobular hole 35 can be efficiently removed. Also, when the slits 37 extend from one of the corners of the hexalobular hole 35, it is easy to prevent a decrease in strength of the head 29 of the fixing screw 7 caused by the formation of the slits 37.

As shown in the example in FIG. 6, the slit 37 may have a bottom surface 39 and a pair of inner wall surfaces 41, or as shown in the example in FIGS. 10 and 11, the slit 37 may further have a concave curved surface 37e connecting the bottom surface 39 and the pair of inner wall surfaces 41.

When the rear end face of the head 29 of the fixing screw 7 is viewed from the front, the width W of the slit 37 may be constant from the portion connected to the hexlobe hole 35 to the outer edge of the head 29, as in the example shown in Figure 6, or the slit 37 may have a portion 37a where the width W increases with increasing distance from the hexlobe hole 35, as in the example shown in Figure 7. When the slit 37 has a portion 37a where the width W increases with increasing distance from the hexlobe hole 35, chips are less likely to become clogged in the slit 37. This improves chip discharge.

The portion 37a where the width W is wider may be located in only a part of the slit 37 as shown in FIG. 6, or may be located in the entire slit 37, that is, from the end of the slit 37 connected to the hexlobe hole 35 to the end located on the outer edge of the head 29. For example, as shown in FIG. 7, the portion 37a where the width W is wider may be located away from the end 37d of the slit 37 connected to the hexlobe hole 35.

In this case, the thickness of the head 29 near the hexlobe hole 35 is easily ensured. Therefore, the hexlobe hole 35 is less likely to deform, and the fixing screw 7 can be stably attached and detached using a hexlobe-shaped tool. In addition, if the portion 37a, whose width W increases with distance from the hexlobe hole 35, reaches the outer edge of the head 29, the chip outlet in the slit 37 becomes wider, making it easier to discharge the chips in the slit 37 to the outside of the slit 37.

The width W of the slit 37 in the above means the width W of the slit 37 in a direction perpendicular to the direction in which the slit 37 extends when the rear end face of the head 29 of the fixing screw 7 is viewed from the front. In the case where the slit 37 has a pair of inner wall surfaces 41, the width W of the slit 37 in the above may be evaluated based on the distance between the pair of inner wall surfaces 41.

As shown in the example in Figure 8, the slit 37 may have a portion 37b where the depth D becomes shallower with increasing distance from the hexalobular hole 35. Here, an imaginary plane S is set that is perpendicular to the central axis O2 of the fixing screw 7 and tangent to the rear end face of the head 29 of the fixing screw 7. The length from this imaginary plane S to the bottom (bottom face 39) of the fixing screw 7 in the direction along the central axis O2 of the fixing screw 7 is defined as the depth D of the slit 37.

This configuration improves the ability to discharge chips to the outside. This is because the slit 37 has a portion 37b where the depth D is shallow, making it easier for the chips to move upward.

The portion 37b where the depth D is shallow may be located in only a part of the slit 37, or may be located in the entire slit 37, that is, from the end of the slit 37 connected to the hexlobe hole 35 to the end located on the outer edge of the head 29. In this case, for example, as in the example shown in Figure 8, the portion 37b where the depth D is shallow may be separated from the end 37d of the slit 37 connected to the hexlobe hole 35.

In this case, the chips flow smoothly from the hexalobular hole 35 to the slit 37. Therefore, the chips are less likely to clog the slit 37. When the portion 37b where the depth D becomes shallow reaches the outer edge of the head 29, the chips can be directed upward at the chip outlet of the slit 37. This makes the chips flow even smoother into the slit 37, making it easier to expel the chips in the slit 37 to the outside of the slit 37.

Also, as shown in the example in Figure 9, the depth D of the slit 37 may be constant, i.e., the bottom (bottom surface 39) of the fixing screw 7 may be located on the same plane as the bottom surface 39 of the hexalobular hole 35.

When the slit 37 has a bottom surface 39 and a pair of inner wall surfaces 41, the pair of inner wall surfaces 41 may have a constant spacing H as they move away from the bottom surface 39, as in the example shown in FIG. 10, or may have a portion where the spacing H becomes wider as they move away from the bottom surface 39. That is, as in the example shown in FIG. 11, the width of the slit 37 is not constant in the direction along the central axis O2 of the fixing screw 7, and the slit 37 may have a portion 37c where the width of the slit 37 increases as it moves closer to the imaginary plane S described above.

In this case, the chips flow smoothly from the slit 37 to the top surface of the head 29. Therefore, the chips are less likely to clog the slit 37. If the portion 37c where the width of the slit 37 increases reaches the top surface of the head 29, the chip outlet in the slit 37 becomes wider, making it easier to discharge the chips in the slit 37 to the outside of the slit 37.

The seat surface 43 in the head 29 may be a plane perpendicular to the central axis O2 of the fixing screw 7, or may be tapered away from the central axis O2 of the fixing screw 7 as it moves away from the shaft portion 31, as in the example shown in FIG. 5. The slit 37 may open in such a seat surface 43 (see FIGS. 8 and 9).

In the example shown in FIG. 3, the through hole 17 of the insert 5 has a central portion 17a, a first conical portion (frustoconical portion) 17b, and a second conical portion (frustoconical portion) 17c. The seat surface 43 of the head 29 abuts against the first conical portion 17b. In this case, the chips that pass through the slit 37 come into contact with the first conical portion 17b. At this time, since the first conical portion 17b has a truncated cone shape whose inner diameter increases as it moves away from the central portion 17a, the chips tend to move upward along the first conical portion 17b. In other words, the chips are easily discharged to the outside, and the chips that have entered the hexlobe hole 35 can be stably removed.

The size of the insert 5 is not particularly limited. For example, the maximum width of the upper surface 11 may be set to approximately 3 to 20 mm. Also, the height from the upper surface 11 to the lower surface 13 may be set to approximately 5 to 20 mm.

The material of the insert 5 may be, for example, a cemented carbide or a cermet. The composition of the cemented carbide may be, for example, WC-Co, WC-TiC-Co, or WC-TiC-TaC-Co. Here, WC, TiC, and TaC are hard particles, and Co is the binder phase.

Cermets are sintered composite materials in which ceramic components are combined with metals. One example of a cermet is a titanium compound whose main component is titanium carbide (TiC) or titanium nitride (TiN). However, it goes without saying that the material of the insert 5 is not limited to the above composition.

The surface of the insert 5 may be coated with a film using a chemical vapor deposition (CVD) method or a physical vapor deposition (PVD) method. The composition of the film may include titanium carbide (TiC), titanium nitride (TiN), titanium carbonitride (TiCN), and alumina (Al2O3).

<Method of manufacturing machined product>
Next, a non-limiting method for manufacturing a machined product having one surface according to the present disclosure will be described with reference to Figs. 12 to 14. Figs. 12 to 14 show a method for manufacturing a machined product when cutting is performed using the above-mentioned cutting tool 1. In Figs. 12 to 14, the rotation axis O1 of the cutting tool 1 is indicated by a two-dot chain line. The machined product 103 is produced by cutting a workpiece 101.

The method for manufacturing a machined product may include the following steps:
(1) rotating a cutting tool 1 as typified by the above-described embodiment;
(2) contacting the rotating cutting tool 1 with the workpiece 101;
(3) a step of separating the cutting tool 1 from the workpiece 101;
may also be provided.

Specifically, first, as shown in FIG. 12, the cutting tool 1 may be rotated in the Y1 direction around the rotation axis O1 while being brought relatively close to the workpiece 101. Next, as shown in FIG. 13, the cutting edge of the cutting tool 1 may be brought into contact with the workpiece 101 to cut the workpiece 101. Then, as shown in FIG. 14, the cutting tool 1 may be moved relatively away from the workpiece 101.

The workpiece 101 may be fixed and the cutting tool 1 may be brought closer. Also, as in the example shown in Figures 12 to 14, the workpiece 101 may be fixed and the cutting tool 1 may be rotated around the rotation axis O1. Also, as in the example shown in Figure 14, the workpiece 101 may be fixed and the cutting tool 1 may be moved away. In the example shown in Figures 12 to 14, the workpiece 101 is fixed and the cutting tool 1 is moved in each process, but of course this is not limited to this form.

For example, in step (1), the workpiece 101 may be brought closer to the cutting tool 1. Also, in step (3), the workpiece 101 may be moved away from the cutting tool 1. To continue cutting, the cutting tool 1 may be kept rotating and the process of contacting the cutting edge of the insert 5 with different locations on the workpiece 101 may be repeated.

Typical examples of materials for the workpiece 101 include carbon steel, alloy steel, stainless steel, cast iron, and non-ferrous metals.

This disclosure is not limited to the above-described embodiments, and various modifications are possible within the scope of the claims. Embodiments obtained by appropriately combining the technical means disclosed in different embodiments are also included in the technical scope of this disclosure.

1 Cutting tool 3 Holder 5 Insert (cutting insert)
7 Fixing screw 9 Pocket 11 Upper surface 13 Lower surface 15 Side surface 17 Through hole 17a Central portion 17b First conical portion (frustum-shaped portion)
17c Second conical portion (frustum-shaped portion)
29 Head 31 Shank 35 Hexalobular hole 37 Slit 39 Bottom surface 41 Inner wall surface 43 Bearing surface 101 Workpiece 103 Cutting workpiece

Claims (7)

a holder having a pocket;
an insert attached to the holder;
a fixing screw for fixing the insert to the holder;
The fixing screw has a shank and a head,
The head portion includes:
Hexlobe hole,
a slit extending from a corner of the hexlobe hole to an outer edge of the head. The cutting tool of claim 1, wherein the slit has a portion that becomes wider as it moves away from the hexlobe hole. The cutting tool according to claim 1 or 2, wherein the slit has a portion whose depth decreases with increasing distance from the hexlobe hole. The slit has a bottom surface and a pair of inner wall surfaces connected to the bottom surface,
The cutting tool according to claim 1 , wherein the pair of inner wall surfaces have portions where the distance therebetween increases with increasing distance from the bottom surface. The head has a seat surface that abuts against the insert,
The seat surface has a tapered shape that moves away from the central axis of the fixing screw as it moves away from the shaft portion,
The cutting tool according to claim 1 , wherein the slit is open in the seating surface. the insert has an upper surface, a lower surface, a side surface, and a through hole that opens on the upper surface and the lower surface and through which the fixing screw is inserted;
6. The cutting tool according to claim 5, wherein the through hole has a central portion located at a center in a direction from the upper surface to the lower surface and having a constant inner diameter, and a truncated conical portion located from the central portion toward the upper surface and having an inner diameter that increases with increasing distance from the central portion. Rotating the cutting tool according to any one of claims 1 to 6;
contacting the rotating cutting tool with a workpiece;
and removing the cutting tool from the workpiece.

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