Indexable cutting tools

Abstract

To provide a blade tip replaceable cutting tool comprising a small-diameter brazing holder that sufficiently ensures rigidity of a steel head part even though comprising a gas exclusion mechanism during brazing.SOLUTION: A blade tip replaceable tool comprises a brazing holder having a tool diameter of φ8 mm or less, and a cutting insert. A steel head part has a fitting seat at a tip, and a recess formed at a rear end part thereof. A protrusion including a tapered surface is formed at a tip of a carbide shank part. A tip of a through hole of the carbide shank part opens into a dead space in the brazing folder. The dead space communicates with an exterior space of the brazing holder via only the through hole. A ratio of a diameter D1 of the through hole to a maximum diameter D2 of the protrusion of the carbide shank part is 10.0% or more and 50.0% or less. A taper angle θ is 40°≤θ≤60°. A ratio of a length Ls of a solid part to an entire length L2 of the steel head part is 5% or more and 25% or less.SELECTED DRAWING: Figure 6

Description

Technical Field

[0001] The present invention relates to a cutting tool with an exchangeable cutting edge.

Background Art

[0002] Conventionally, there is known a brazed holder in which a steel head portion and a carbide shank portion are joined by brazing to enhance rigidity. In the brazing process, a brazing material is sandwiched between the joining surfaces of the steel head portion and the carbide shank portion, and the sandwiched brazing material is heated from the outside to melt and joined. In order to wet and spread the brazing material on the surface of each joining surface, the oxide film on the surface of the joining surface is removed, but at that time, gas is generated, so it is necessary to provide a gas vent hole. As the form of the gas vent hole, a side hole that penetrates the steel head portion in the radial direction and opens to the side surface is known (see Non-Patent Document 1). Five holder photographs are published on the second page of Non-Patent Document 1. Among them, three of the smaller-diameter ones are brazed holders, and a side hole can be confirmed in the holder with the smallest tool diameter.

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Non-Patent Documents

[0004]

Non-Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0005] If the side holes in the steel head are used as gas vents, a small tool diameter increases the proportion of the gas vents to the volume of the steel head, raising concerns about stress concentration leading to breakage and deterioration of dynamic balance. On the other hand, as described in Patent Document 1, when a coolant hole is provided that penetrates the steel head portion and the carbide shank portion in the axial direction, the coolant hole also functions as a gas vent. When the tool diameter is large, the ratio of the through hole to the tool diameter in terms of cross-sectional area is small, so it is relatively easy to secure the necessary tool rigidity. However, when the tool diameter is small, the ratio of the coolant hole to the tool diameter is large, making it difficult to secure the necessary tool rigidity in the steel head portion.

[0006] This invention has been made in view of the above circumstances, and aims to provide an interchangeable cutting tool equipped with a small-diameter brazing holder that ensures sufficient rigidity of the steel head portion while also having a gas elimination mechanism during brazing. [Means for solving the problem]

[0007] (1) An interchangeable cutting tool according to one aspect of the present invention is an interchangeable cutting tool comprising a brazed holder with a tool diameter of φ8 mm or less, in which a steel head portion made of steel and a carbide shank portion made of cemented carbide are joined axially by brazing, and a cutting insert mounted on the steel head portion. The tip of the steel head portion is provided with a mounting seat on which at least one cutting insert can be attached. The rear end of the steel head portion has a recess formed therein, which opens toward the cemented carbide shank portion and includes a concave tapered surface that forms a joint with the cemented carbide shank portion. The tip of the cemented carbide shank portion has a convex portion formed therein, which includes a tapered surface that fits into the concave tapered surface of the steel head portion. The cemented carbide shank portion has a through hole that penetrates axially through the radial center of the cemented carbide shank portion. The tip of the through hole opens into a space within the brazed holder surrounded by the recess of the steel head portion and the convex portion of the cemented carbide shank portion. The aforementioned cavity is connected to the external space of the brazing holder only through the through hole. When the diameter of the through hole is D1 and the maximum diameter of the protrusion of the carbide shank is D2, the ratio of D1 to D2 satisfies the relationship of 10.0% to 50.0%. The taper angle θ of the tapered surface of the carbide shank is 40° ≤ θ ≤ 60°. When the total axial length of the steel head with the cutting insert attached is L2, and the axial length of the solid portion of the steel head that has a solid, perpendicular cross-section from the central axis to the outer circumference is Ls, the ratio of Ls to L2 is 5% to 25%.

[0008] According to the above configuration, the length Ls of the solid portion of the steel head is 5% or more of the total length L2 of the steel head, thus reducing the risk of breakage from the outer circumference of the steel head, ensuring sufficient rigidity in the steel head, and obtaining sufficient tool rigidity even for small diameter tools of φ8 mm or less. Furthermore, the ratio of the diameter D1 of the through hole to the maximum diameter D2 of the convex portion of the carbide shank is in the range of 10.0% to 50.0%, and the taper angle θ is in the range of 40° to 60°, making it possible to achieve both the formation of a gas vent hole and the securing of the necessary tool rigidity.

[0009] (2) In (1), when the axial distance from the tip of the cutting insert to the tip of the cavity is L1, the ratio L1 / L2 of the distance L1 to the total length L2 of the steel head portion may be 45% ≤ L1 / L2 ≤ 60%.

[0010] (3) In (1) or (2), when the total axial length of the replaceable tip cutting tool is L3, the total length L2 of the steel head portion may be configured to be 18.0% or less of the total length L3 of the replaceable tip cutting tool.

[0011] (4) In any one of (1) to (3), the steel head portion may be made of steel with a hardness of 35 HRC or higher, and the carbide shank portion may be made of a cemented carbide alloy with a hardness of 80 HRC or higher. [Effects of the Invention]

[0012] According to one aspect of the present invention, a replaceable cutting edge tool is provided, which has a small-diameter brazing holder that ensures sufficient rigidity of the steel head portion while also having a gas removal mechanism during brazing. [Brief explanation of the drawing]

[0013] [Figure 1] Figure 1 is a side view of an interchangeable-tip cutting tool according to an embodiment. [Figure 2] Figure 2 is a front view of the replaceable-tip cutting tool shown in Figure 1, viewed from the axial tip side. [Figure 3] Figure 3 is an exploded perspective view of the brazing holder. [Figure 4] Figure 4 is a three-view drawing of the steel head section. [Figure 5] Figure 5 shows the joint structure between the steel head and the carbide shank. [Figure 6] Figure 6 shows the dimensions of each part of an interchangeable-tip cutting tool. [Modes for carrying out the invention]

[0014] FIG. 1 is a side view of the cutting tool with replaceable cutting edges of the present embodiment. FIG. 2 is a front view of the cutting tool with replaceable cutting edges shown in FIG. 1 as viewed from the tip side in the axial direction. FIG. 3 is an exploded perspective view of the brazing holder. FIG. 4 is a three-view drawing of the steel head portion. FIG. 5 is a view showing the joining structure of the steel head portion and the carbide shank portion.

[0015] The cutting tool with replaceable cutting edges 1 of the present embodiment includes a brazing holder 2 and a cutting insert 3 mounted on the brazing holder 2. The brazing holder 2 has a structure in which a steel head portion 4 made of steel and a carbide shank portion 5 made of cemented carbide are axially joined by brazing along the central axis O. The brazing holder 2 is a small-diameter holder with a tool diameter of φ8 mm or less.

[0016] In the following description, along the axial direction of the central axis O of the cutting tool with replaceable cutting edges 1, the direction from the carbide shank portion 5 toward the steel head portion 4 is referred to as the tip side, and the direction from the steel head portion 4 toward the carbide shank portion 5 is referred to as the rear end side. Also, the direction perpendicular to the central axis O of the cutting tool with replaceable cutting edges 1 is referred to as the radial direction, and the direction that circulates around the central axis O is referred to as the circumferential direction.

[0017] The cutting tool with replaceable cutting edges 1 of the present embodiment is a ball end mill with replaceable cutting edges. The cutting tool with replaceable cutting edges 1 is rotatable about the central axis O. Therefore, the central axis O of the cutting tool with replaceable cutting edges 1 is the tool rotation axis of the cutting tool with replaceable cutting edges 1.

[0018] The cutting insert 3 is attached to the steel head portion 4 of the cutting tool with replaceable cutting edges 1, and the rear end portion of the carbide shank portion 5 is gripped by the spindle of the machine tool. The cutting tool with replaceable cutting edges 1 is rotated in the tool rotation direction T about the central axis O while being fed in a direction intersecting the central axis O, and thus cutting is performed on the workpiece by a plurality of cutting edges 31 provided on the cutting insert 3.

[0019] The cutting insert 3 is made of, for example, a cemented carbide. The cemented carbide shank portion 5 is preferably made of a cemented carbide with a hardness of 80 HRC or higher. The cutting insert 3 comprises a plate-shaped insert body 3a and a plurality of cutting edges 31 formed at the tip of the insert body 3a. In this embodiment, the cutting edges 31 are ball-shaped cutting edges whose rotational trajectory around the central axis O forms a hemispherical shape. Two cutting edges 31 are positioned at 180° rotationally symmetrical positions around the central axis O. The insert body 3a is provided with a through hole that penetrates the insert body 3a in the thickness direction. A fixing screw 12 is passed through the through hole in the insert body 3a when fixing the cutting insert 3 to the steel head portion 4.

[0020] The cutting insert 3 in this embodiment has two blades, but it may also have one blade or three or more blades. Multiple cutting inserts may be mounted on the steel head portion 4. The replaceable tip cutting tool 1 may be a radius end mill or a square end mill.

[0021] A mounting seat 8 is provided at the tip of the steel head portion 4, to which a cutting insert 3 can be attached. The cutting insert 3 is positioned on the mounting seat 8 with its central axis (insert central axis) aligned with the central axis of the brazed holder 2. In other words, the central axis of the brazed holder 2 and the central axis of the cutting insert 3 are coaxial with each other. Furthermore, the central axes of the cutting insert 3 and the central axis of the brazed holder 2 coincide with the central axis O of the replaceable-tip cutting tool 1.

[0022] The steel head portion 4 is made of steel. Preferably, the steel head portion 4 is made of steel with a hardness of 35 HRC or higher. As shown in Figure 4, the steel head portion 4 is generally cylindrical. A mounting seat 8, which consists of a groove into which a cutting insert 3 is inserted, is provided at the tip of the steel head portion 4. As shown in Figure 4(A), the mounting seat 8 is generally rectangular when viewed from the axial tip side of the steel head portion 4. The bottom surface 8a of the mounting seat 8 is a plane perpendicular to the central axis O.

[0023] The groove-shaped mounting seat 8 is formed, dividing the tip of the steel head portion 4 into two gripping portions 4A and 4B. The gripping portions 4A and 4B each extend axially at the tip of the steel head portion 4. A through hole 9A is formed in gripping portion 4A, passing through it radially. A screw hole 9B is formed in gripping portion 4B, passing through it radially. The male screw portion of the fixing screw 12, which fixes the cutting insert 3, is fitted into the female screw portion of the screw hole 9B.

[0024] The cutting insert 3 is inserted into a mounting seat 8, which is sandwiched between the gripping portions 4A and 4B. With the cutting insert 3 installed on the mounting seat 8, the through hole 9A of the gripping portion 4A, the through hole of the cutting insert 3, and the screw hole 9B of the gripping portion 4B are positioned coaxially. The cutting insert 3 is fixed to the steel head portion 4 by inserting the fixing screw 12 from the through hole 9A side and tightening the fixing screw 12 into the screw hole 9B.

[0025] As shown in Figure 4(B), the gripping portions 4A and 4B have a shape that is asymmetrical with respect to the central axis O when viewed from the axial direction of the screw hole 9B. Specifically, the gripping portions 4A and 4B have a shape in which the portion on the rear side in the tool rotation direction T is cut out. As a result, as shown in Figure 1, when the cutting insert 3 is mounted, the rake face of the cutting edge 31 is exposed from the gripping portions 4A and 4B. On the other hand, the surface of the cutting insert 3 opposite to the rake face is covered by the gripping portions 4A and 4B. The grooves including the rake faces of the two cutting edges 31 and the side end faces 4a and 4b (see Figure 4) of the gripping portions 4A and 4B become the chip evacuation grooves for each cutting edge 31. Furthermore, in this embodiment, as shown in Figure 4, notches 15A and 15B are provided on the side surface of the steel head portion 4, extending the side end faces 4a and 4b to the rear side of the bottom surface 8a of the mounting seat 8. The notches 15A and 15B also function as part of the chip evacuation groove.

[0026] A recess 7 is formed at the rear end of the steel head portion 4, opening toward the carbide shank portion 5. The recess 7 has a concave tapered surface 7a that narrows from the rear end to the tip of the steel head portion 4, and a concave cylindrical surface 7b that extends further toward the tip from the tip of the concave tapered surface 7a. In this embodiment, the diameter of the concave tapered surface 7a at the rear end is the same as the diameter of the steel head portion 4. In this embodiment, the diameter of the concave cylindrical surface 7b is approximately the same as the diameter D1 of the through hole 11 of the carbide shank portion 5, which will be described later. In this embodiment, a concave conical surface extending toward the tip is formed at the tip of the concave cylindrical surface 7b. However, this represents the shape of the hole when the concave cylindrical surface 7b is machined with a drill, and a flat surface may also be used.

[0027] The carbide shank portion 5 is cylindrical, extending along the central axis O. The carbide shank portion 5 has a convex portion 6 at its tip that tapers toward the tip. The outer circumferential surface of the convex portion 6 is a tapered surface 6a that fits into the concave tapered surface 7a of the steel head portion 4. The carbide shank portion 5 has a through hole 11 that penetrates the carbide shank portion 5 in the axial direction. The through hole 11 has a circular cross-section coaxial with the carbide shank portion 5. The through hole 11 opens at the tip of the convex portion 6. The diameter of the tip of the convex portion 6 is approximately the same as the opening diameter of the tip of the through hole 11. The convex portion 6 is trapezoidal when viewed radially.

[0028] As shown in Figure 5, the steel head portion 4 and the carbide shank portion 5 are fixed together by brazing. Specifically, the convex portion 6 of the carbide shank portion 5 is inserted into the recess 7 of the steel head portion 4, and the tapered surface 6a of the convex portion 6 and the concave tapered surface 7a of the recess 7 are brazed together. The tapered surface 6a and the concave tapered surface 7a constitute the joint portion 13.

[0029] As shown in Figure 5(A), when the steel head portion 4 and the carbide shank portion 5 are brazed together, the convex portion 6 of the carbide shank portion 5 is accommodated within the axial range of the concave tapered surface 7a. As a result, a cavity 14 is formed inside the steel head portion 4, surrounded by the recess 7 of the steel head portion 4 and the convex portion 6 of the carbide shank portion 5. In this embodiment, the cavity 14 is the space surrounded by the concave cylindrical surface 7b of the recess 7. The tip of the convex portion 6 may also be located within the axial range of the concave cylindrical surface 7b.

[0030] The tip end of the through hole 11 in the carbide shank portion 5 is located at the rear end of the concave cylindrical surface 7b. The through hole 11 in the carbide shank portion 5 opens into the cavity 14. The joint 13 between the concave tapered surface 7a and the tapered surface 6a is sealed by brazing. Furthermore, the steel head portion 4 does not have a ventilation hole that penetrates the steel head portion 4 radially and leads to the cavity 14. Therefore, the cavity 14 is connected to the external space of the brazing holder 2 only through the through hole 11.

[0031] The cavity 14 functions as a discharge point for excess brazing material pushed out from the joint 13 during the process of joining the concave tapered surface 7a and the tapered surface 6a. This makes it easier to control the thickness of the brazing material located between the concave tapered surface 7a and the tapered surface 6a. This improves the dimensional accuracy of the replaceable tip cutting tool 1. It also suppresses variations in the joint strength of the joint 13 from product to product.

[0032] The through-hole 11 functions as a passage for venting gas generated from the brazing material to the outside during the process of joining the concave tapered surface 7a and the tapered surface 6a. If the cavity 14 is sealed from the outside, the internal pressure will increase due to the generated gas, which may cause the brazing material at the joint 13 to be pushed out or cause air bubbles to be mixed into the joint surface, potentially reducing the joint strength. According to this embodiment, problems caused by gas during brazing are eliminated, and sufficient joint strength can be obtained.

[0033] In this embodiment, the replaceable tip cutting tool 1 is configured such that the dimensions of each part shown in Figure 6 satisfy a predetermined range or size relationship. First, when the diameter of the through hole 11 in the carbide shank portion 5 is D1 and the maximum diameter of the protrusion 6 in the carbide shank portion 5 is D2, the ratio of D1 to D2 satisfies the relationship of 10.0% or more and 50.0% or less. If the ratio of D1 to D2 is less than 10.0%, the through hole 11 becomes very narrow, making it easier for the brazing material flowing to the tip of the carbide shank 5 to block the opening of the through hole 11. When the through hole 11 is blocked, problems such as a decrease in joint strength due to gases generated during brazing are more likely to occur. If the ratio of D1 to D2 is greater than 50.0%, a large opening is formed at the tip of the protrusion 6 of the carbide shank portion 5, thus reducing the area of ​​the tapered surface 6a. As the brazing area decreases, it becomes difficult to ensure sufficient joint strength.

[0034] The taper angle θ of the tapered surface 6a of the carbide shank portion 5 is between 40° and 60°. The taper angle of the concave tapered surface of the steel head portion 4 matches the taper angle θ of the tapered surface 6a to be joined. If the taper angle θ is less than 40°, the wall thickness on the radially outer side of the concave tapered surface 7a in the steel head portion 4 will be reduced, which may reduce the rigidity of the steel head portion 4. If the taper angle θ exceeds 60°, the area of ​​the tapered surface 6a will decrease, reducing the joining area of ​​the joint portion 13, making it difficult to ensure joint strength.

[0035] When the total axial length of the steel head portion 4 with the cutting insert 3 attached is L2, and the axial length of the solid portion 20 of the steel head portion 4, which has a solid, perpendicular cross-section from the central axis O to the outer circumference, is Ls, the ratio of Ls to L2 is 5% or more and 25% or less. In this embodiment, the solid portion 20 is the cylindrical part of the steel head portion 4 sandwiched between the rear ends of the notches 15A and 15B and the front end of the recess 7. The depth of the notches 15A and 15B varies depending on the shape of the cutting insert 3, and depending on the depth of the notches 15A and 15B, the rigidity of the steel head portion 4 may decrease. Therefore, the solid portion 20 is defined as the part that does not include both the notches 15A and 15B and the recess 7 which is the hollow part of the steel head portion 4. If the ratio of Ls to L2, Ls / L2, is less than 5%, the proportion of the solid portion 20 in the steel head portion 4 is too small, resulting in insufficient rigidity of the steel head portion 4. If Ls / L2 is greater than 25%, the taper angle θ becomes too large relative to the steel head portion. As a result, the area of ​​the tapered surface 6a decreases, and there is a risk that a sufficient brazing area cannot be secured. Ls / L2 is preferably 7.5% or more, and more preferably 10.0% or more.

[0036] The steel head portion 4 of this embodiment does not have a hole that penetrates the steel head portion 4 in the axial direction. The steel head portion described in Patent Document 1 has a hole that penetrates the steel head portion in the axial direction as a coolant hole. While such a through hole does not cause problems with large-diameter or medium-diameter tools, when applied to small-diameter tools, the ratio of the hollow portion (coolant hole) to the tool becomes large, which may result in insufficient tool rigidity. Furthermore, even if a solid portion is provided in part of the steel head portion, if the size of the solid portion is insufficient, it will not contribute to improving the rigidity of the steel head portion. In this embodiment, a solid portion 20 is provided, and Ls / L2 is set to the above range, thereby ensuring rigidity even for small-diameter tools of φ8 mm or less.

[0037] When L1 is the axial distance from the tip of the cutting insert 3 to the tip of the cavity 14, it is preferable that the ratio L1 / L2 of the distance L1 to the total length L2 of the steel head portion 4 is 45% ≤ L1 / L2 ≤ 60%. If the ratio L1 / L2 is less than 45%, the volume of the cavity 14 increases, and the proportion of the hollow portion increases, making it difficult to ensure the overall rigidity of the steel head portion 4. If the ratio L1 / L2 is greater than 60%, it becomes difficult to secure the volume of the cavity 14, and the through hole 11 is more likely to be blocked by excess brazing material.

[0038] When the total axial length of the replaceable tip cutting tool 1 is L3, the total length L2 of the steel head portion 4 is preferably 18.0% or less of the total length L3 of the replaceable tip cutting tool 1. The configuration of the steel head portion 4 in this embodiment described above is suitable for a replaceable tip cutting tool 1 having a total length exceeding 5.5 times the total length L2 of the steel head portion 4. A replaceable tip cutting tool 1 equipped with a steel head portion 4 with the above configuration makes it easier to ensure the overall rigidity of the cutting tool. [Examples]

[0039] To confirm the effects of the present invention, the steel head portions of Examples 1 to 3 and Comparative Example 1 shown in Table 1 were brazed to the carbide shank portions to create replaceable cutting tools. The carbide shank is made of a cemented carbide alloy with a hardness of 68 HRC, and has a length of 75.5 mm, a through hole diameter D1: 1.5 mm, and a maximum diameter D2: 5.5 mm. The taper angle θ of the convex tip is as shown in Table 1.

[0040] [Table 1]

[0041] In the replaceable cutting tools of the present invention examples 1 to 3, the ratio of the diameter D1 of the through hole to the maximum diameter D2 of the protrusion of the carbide shank is in the range of 10.0% to 50.0%, the taper angle θ of the tapered surface of the carbide shank is in the range of 40° ≤ θ ≤ 60°, and the ratio of the length Ls of the solid part to the total length L2 of the steel head is in the range of 5% to 25%. In the replaceable-tip cutting tools of the present invention examples 1 to 3, sufficient area can be secured at the joint between the steel head and the carbide shank, and sufficient joint strength can be obtained. Here, for ◎〇△ listed in Table 1, ◎ indicates a joint area of ​​60 mm². 2 The "Super" and "〇" indicate a joint area of ​​55mm². 2 The above is 60 or less, and △ indicates a joint area of ​​55 mm². 2 It is less than [value missing]. The evaluation level is based on the measurement results of the joint strength in the actual machine. In the tool diameter of the example, the joint area between the steel head and the carbide shank is 55 mm². 2Experiments have confirmed that, if the above conditions are met, sufficient joint strength can be obtained for loads within the specified range of the replaceable tip cutting tool. Furthermore, the joint area is 60 mm². 2 Experiments have confirmed that, in the case of "Super," it is possible to obtain a bonding strength that can withstand cutting conditions exceeding the specified range of the replaceable tip cutting tool. On the other hand, in the indexable cutting tool of Comparative Example 1, where the taper angle θ exceeds 60°, sufficient joint strength could not be obtained because the joint area between the steel head and the carbide shank was small. [Explanation of symbols]

[0042] 1…Indexable cutting tool, 2…Holder, 3…Cutting insert, 4…Steel head, 5…Carbide shank, 6…Convex part, 6a…Tapered surface, 7…Concave part, 7a…Concave tapered surface, 8…Mounting seat, 11…Through hole, 13…Joint, 14…Cavity, 20…Solid part, D1…Diameter of the through hole, D2…Maximum diameter of the convex part of the carbide shank, L1…Axial distance from the tip of the cutting insert to the tip of the cavity, L2…Total length of the steel head with the cutting insert attached, L3…Total length of the indexable cutting tool, Ls…Axial length of the solid part, O…Center axis, θ…Taper angle

Claims

1. A replaceable cutting tool comprising a brazed holder with a tool diameter of φ8 mm or less, in which a steel head portion made of steel and a carbide shank portion made of cemented carbide are joined axially by brazing, and a cutting insert mounted on the steel head portion, The tip of the steel head portion is provided with a mounting seat to which at least one cutting insert can be attached. The rear end of the steel head portion has a recess formed therein, which opens toward the carbide shank portion and includes a concave tapered surface that forms a joint with the carbide shank portion. The tip of the carbide shank portion has a convex portion that includes a tapered surface that fits into the concave tapered surface of the steel head portion. The carbide shank portion has a through hole that penetrates the radial center of the carbide shank portion in the axial direction, The tip of the through hole opens into a cavity within the brazing holder, which is surrounded by the recess of the steel head portion and the protrusion of the carbide shank portion, and this cavity is connected to the external space of the brazing holder only through the through hole. When the diameter of the through hole is D1 and the maximum diameter of the protrusion of the carbide shank is D2, the ratio of D1 to D2 satisfies the relationship of 10.0% or more and 50.0% or less. The taper angle θ of the tapered surface of the carbide shank portion is 40° ≤ θ ≤ 60°. When the total axial length of the steel head portion with the cutting insert attached is L2, and the axial length of the solid portion of the steel head portion having a solid, perpendicular cross-section from the central axis to the outer circumference is Ls, the ratio of Ls to L2 is 5% or more and 25% or less. Interchangeable tip cutting tool.

2. When L1 is the axial distance from the tip of the cutting insert to the tip of the cavity, The ratio L1 / L2 of the distance L1 to the total length L2 of the steel head portion is 45% ≤ L1 / L2 ≤ 60%. The replaceable tip cutting tool according to claim 1.

3. When the total axial length of the aforementioned replaceable-tip cutting tool is L3, The total length L2 of the steel head portion is 18.0% or less of the total length L3 of the replaceable-tip cutting tool. The replaceable tip cutting tool according to claim 1 or 2.

4. The steel head portion is made of steel with a hardness of 35 HRC or higher. The carbide shank portion is formed of a cemented carbide alloy with a hardness of 80 HRC or higher. The replaceable tip cutting tool according to claim 1 or 2.

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