JP3042053B2 - Cutting tool and manufacturing method thereof - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a throw-away type cutting tool to which a throw-away tip is detachably mounted.

[0002]

2. Description of the Related Art In recent years, in the field of cutting tools, a throw-away tip (hereinafter abbreviated as a chip) made of a hard material such as a cemented carbide is detachably attached to a tool body made of a steel material such as tool steel. The so-called throw-away type mounted is widely used. In such a throw-away type tool, in order to prevent damage to the outer peripheral surface of the tool body due to rubbing with chips and enhance the durability of the tool body, the tool body is subjected to a quenching treatment to reduce the surface hardness to H. _R C
It is being raised to about 45.

[0003]

However, when quenching is performed on the tool body, quenching distortion is inevitably generated.
For this reason, parts requiring high precision, such as the boss surface of the milling tool body and the outer peripheral surface of the shank of the end mill, or parts that require precision, such as chip mounting grooves, are polished to remove distortion after quenching. Processing and cutting by an end mill have to be performed, and an increase in cost due to an increase in the number of processing steps is inevitable. In addition, depending on the magnitude of the quenching strain, the processing time becomes extremely long, and the processing cost may be further reduced.

[0004] Further, in the case of cutting after quenching, because the surface hardness of the tool body is a H _R C45 or a high hardness, severe wear of the cutting edge of the end mill to be used for machining, the machining accuracy The impact was not too small. In particular, when a plurality of chip mounting grooves are continuously processed, the processing accuracy between the chip mounting groove formed immediately after the start of processing due to wear of the cutting tool and the chip mounting groove formed immediately before the end of the processing is improved. This drastically changed, and accordingly, the runout accuracy of the chip attached to the chip attachment groove was remarkably deteriorated.

[0005] In addition, rapid cooling during quenching often causes large residual stress inside the tool main body, and accuracy may be degraded by releasing such stress later.

The present invention has been made under such a background, and the tool body has a high surface hardness and excellent durability.
It is another object of the present invention to provide an inexpensive cutting tool with good accuracy and a method for manufacturing the same.

[0007]

In order to solve the above-mentioned problems, a cutting tool according to the present invention has a plurality of chip mounting grooves formed in a tool body having a mounting portion to a machine tool. A cutting tool detachably mounted, wherein a hardened layer formed by nitriding treatment is formed on a surface layer portion of the tool main body , and further has the following features.
Things.

That is , when a screw hole for mounting a chip or a component such as a wedge member for mounting a chip is formed in the tool body, formation of a hardened layer by nitriding is prevented inside the screw hole. It is preferable to use a nitriding prevention part. In addition, a soft film may be formed on the surface of the hardened layer during the process of forming the hardened layer by nitriding. In such a case, the surface of the mounting portion to the machine tool is polished to cure the mounting portion. The surface of the layer is preferably a polished surface from which the soft coating has been removed. Furthermore, in order to reduce the number of man-hours for manufacturing the tool body, it is preferable to leave the surface of the hardened layer in the chip mounting groove as a bare surface which is not subjected to the finishing after the nitriding. Furthermore, in order to prevent the occurrence of cracks during the nitriding process, it is desirable to perform chamfering or rounding at the corners of the chip mounting groove.

[0009] The hardness of the hardened layer of the tool body listed above is H _V at a position of 0.1 mm from the surface of the tool body.
It is preferred to be 500 or more.

[0010] As a method of manufacturing a cutting tool in which the inside of a screw hole is a nitriding preventing portion, a stub is attached to the screw hole, and then the tool body is subjected to nitriding treatment to harden the surface layer of the tool body. A manufacturing method in which a layer is formed, and thereafter the above-mentioned snoop is removed is preferable. In this case, in order to reduce the manufacturing cost, it is desirable to use a non-nitridable material for the stub, or to form a nitride prevention layer on the surface of the snip and then attach the snip to the screw hole. In order to prevent unnecessary enlargement of the nitriding prevention part of the peripheral part, a tapered surface which increases in diameter toward the opening end of the screw hole is formed at the mouth of the screw hole of the tool body, and It is preferable to use a flathead screw having a tapered surface that can be in close contact with the tapered surface. It should be noted that various screw members such as a hexagon bolt and a set screw are used for the embedding here.

[0011]

In the cutting tool having the above-described structure, a required hardness is given to the surface layer portion of the tool body by the hardened layer formed by the nitriding treatment. In addition, since the heating temperature of the nitriding treatment is sufficiently lower than the quenching temperature of the steel material, there is no possibility that distortion occurs. Therefore, it is not necessary to perform a strain removing process after the nitriding process. Further, since no large residual stress is generated during the nitriding treatment, the stress is not released later and the accuracy is not lost.
In particular, when the inside of the screw hole is used as the nitriding prevention part in the tool body having the screw hole, there is no possibility that the thread hardness of the screw hole is unnecessarily increased to cause cracking or chipping,
There is no damage to the opponent's bolt.

In addition, since the mounting portion of the tool body is a polished surface from which the soft coating has been removed, deformation of the mounting portion when the cutting tool is mounted on the machine tool is prevented, and the reproducibility of the mounting accuracy is improved. be able to. On the other hand, when the hardened layer surface in the chip mounting groove is a bare surface which is not subjected to the finishing process after the nitriding treatment, the trouble after the nitriding treatment can be omitted, especially in the case of a cutting tool having a large number of chip mounting grooves. In addition, the number of processing steps is greatly reduced. Further, when chamfering or rounding is performed on the corners of the chip mounting grooves, stress concentration on the corners is reduced, and cracks in the hardened layer are prevented.

According to the manufacturing method of the cutting tool having the above-described structure, the inside of the screw hole is sealed by the stub mounted in the screw hole, so that the ammonia gas or the nitriding gas supplied around the tool body during the nitriding treatment is used. Intrusion of the nitriding agent such as a solution into the screw hole is prevented, so that the nitriding preventing portion can be easily obtained only by removing the burrs after the nitriding process. In addition, in the case of scrutiny, there is an inconvenience that a desired hardened layer cannot be obtained because the anti-nitriding agent adheres to unnecessary portions as in the case of applying an anti-nitriding agent in a screw hole to prevent nitriding. There is no non-uniformity in the effect of preventing nitridation due to uneven application of the nitriding agent, so that a uniform anti-nitridation portion can be obtained.

Further, in the above manufacturing method, in the case where a non-nitridable material is used for the stub or a nitriding treatment is performed by forming a nitridation preventing layer on the surface of the stub, the splinter does not change before and after the nitriding treatment. The cost required for the nitriding process can be reduced by repeatedly using the embedding.

Further, when a tapered surface is formed at the mouth portion of the screw hole of the tool body, and a flat head screw is used, the tapered surface of the head of the flat head screw and the tapered surface of the screw hole are in close contact. By doing so, the sealability inside the screw hole is further improved and the quality of the anti-nitridation part is improved, while the anti-nitridation agent reliably reaches around the mouth of the screw hole and the hardened layer by the nitriding treatment around the screw hole It can be formed to the limit, and the nitriding preventing portion does not expand unnecessarily.

[0016]

An embodiment of the present invention will be described below with reference to the drawings. 1 to 4 show a throw-away type face milling machine according to the present embodiment. In these figures, reference numeral 1 denotes a tool main body. This tool main body 1 has a tip pocket 2 which is depressed toward the center in the tool radial direction on an outer peripheral portion thereof,
A plurality of chip mounting grooves 2a are formed at equal intervals in the circumferential direction and are continuous with the chip mounting groove 2a connected to the rear end side in the circumferential direction of the chip pocket 2. The chip mounting seat 3 provided at the end of the chip mounting groove 2a Is a rectangular flat sheet 4 placed thereon and fixed with set screws 5. On the upper surface of the sheet 4, a chip 6 formed by molding a cemented carbide into a substantially square flat plate is placed, and the chip 6 is inserted into the chip mounting groove 2a and tightened with a clamp screw 7. It is pressed in the tool circumferential direction by the member 8 and is firmly fixed to the tool body 1. A center hole 9 is formed at the center of the tool body 1, and a boss surface 10 orthogonal to the tool axis is formed around an opening of the center hole 9 on the tool rear end side. The center hole 9 and the boss surface 10 form a mounting portion for mounting the tool main body 1 to a spindle (not shown) of the machine tool.

The tool body 1 is composed of SCM440, SNCM4
The whole is formed in a substantially annular shape using a steel material such as 39 as a material,
The chip mounting groove 2a, the center hole 9, and the boss surface 10 are formed by performing a cutting process. The entire surface of the tool body 1 is subjected to a nitriding treatment, whereby a hardened layer (not shown) having a higher hardness than the inside is formed on the surface layer of the tool body 1. The hardness of the hardened layer is appropriately determined according to the use conditions, the internal hardness, and the like of the tool main body 1.
It is preferable that H _V 500 or more is secured at a depth of 1 mm. And if less than H _V 500 is the difference between the internal hardness of the tool body 1 too small because may not be sufficiently exhibited improvement of tool life is caused.

A known nitriding method is used as a nitriding method of the tool body 1. For example, the tool body 1 is heated in an atmosphere of ammonia gas (NH ₃ ) or another gas containing nitrogen to remove nitrogen atoms. Gas nitriding, in which a nitride layer is formed by infiltrating from the tool surface, is preferably used. In addition, bluing salts (KCN, NaCN) and cyanates (KC
Various methods such as a salt bath nitriding treatment in which the tool main body 1 is heated in a state of being immersed in a mixed solution with NO, NaCNO) and ion nitriding can be used.

The heating temperature of the tool body 1 at the time of nitriding is 500 to 550 ° C. in the case of gas nitriding and less than 600 ° C. in the case of salt bath nitriding. The temperature is much lower than the heating temperature of 850 ° C. or higher. Further, the nitriding time is 2 in the case of gas nitriding.
It takes about 0 to 100 hours, and about 2 to 3 hours in the case of salt bath nitriding. The depth of the hardened layer to be formed is preferably in the range of 0.1 mm to 0.4 mm. When the thickness is 0.1 mm or less, the hardness of the hardened layer is too thin and the hardness is easily lost. On the other hand, when the thickness is 0.4 mm or more, the hardness on the surface side becomes too high and cracks are likely to occur. . Incidentally, in order to achieve the above-mentioned thickness of the hardened layer by gas nitriding, the processing time is preferably set to 20 to 40 hours.

The chip mounting groove 2a, the center hole 9 and the boss surface 10 are formed with a predetermined precision by cutting or grinding before nitriding. However, a soft coating may be formed on the surface layer of the tool main body 1 due to the carbon content of the tool main body 1 bonding with the nitride during the nitriding treatment. In such a case, the center is removed from the boss surface 10 after the nitriding treatment. Only the tool mounting portion (the portion indicated by the one-dot chain line T in FIG. 1) over the hole 9 is polished, and the surface of the hardened layer formed on these mounting portions is a polished surface from which the soft coating has been removed. There is. If you leave the soft coating on the mounting part surface,
This is because, when the tool main body 1 is mounted on the machine tool, the soft coating is deformed to cause mounting errors such as misalignment, and the reproducibility of the mounting accuracy of the tool main body 1 may not be ensured. The thickness of the soft coating is about 0.01 mm at the maximum, and the allowance for polishing for removing the coating is 0.0 mm.
About 5 mm is enough.

On the other hand, the tip mounting groove 2a of the tool body 1
The surface of the hardened layer formed inside the substrate is a bare surface which is not subjected to finishing after the nitriding treatment. This is because, in the case of a milling tool, since the number of the chip mounting grooves 2a is large, if these are finished one by one after the nitriding treatment, the number of manufacturing steps is significantly increased.

Further, as shown in more detail in FIGS. 2 to 4, corners where the wall surfaces of the chip mounting grooves 2a intersect are rounded to form minute curved surfaces 11 and 12. These minute curved surfaces 11 and 12 are for protecting the hardened layer by preventing the occurrence of cracks during the nitriding treatment. Instead of forming these minute curved surfaces 11 and 12, chamfering may be applied to the corners in the chip mounting groove 2a to form minute inclined surfaces obliquely intersecting with the respective wall surfaces.

Thus, in the face mill having the above-described configuration, the surface of the tool main body 1 is given a necessary hardness by performing the nitriding treatment on the tool main body 1. In addition, since the nitriding temperature is much lower than the temperature of the quenching process, a large distortion such as that at the time of the quenching process is required for the center hole 9, the boss surface 10, the chip mounting groove 2a, or the like where accuracy is required. Does not occur. For this reason, it is not necessary to perform a finishing process after the nitriding process, and the number of processing steps and the processing time of the tool main body 1 are greatly reduced, whereby a large reduction in the manufacturing cost is achieved. Even if it is necessary to process the boss surface 10 and the like after the nitriding treatment to remove the soft coating due to the nitriding treatment, the removal margin is much smaller than the strain removal at the time of quenching. No cost pressure. Incidentally, the allowance in this embodiment is 0.05
mm, which is much shorter than the conventional machining allowance after quenching of 0.2 mm or more. Further, since the nitriding temperature is low, a large residual stress does not occur inside the tool body 1, and there is no fear that accuracy is lost due to the subsequent release of the stress. Further, since it is not necessary to finish the tip mounting groove 2a after the nitriding process, deterioration of the runout accuracy due to tool wear at the time of the finishing process does not occur.

Although the present embodiment has been described with reference to an example of a general face mill in which a chip is mounted so that its upper and lower surfaces face the tool circumferential direction, the present invention is not limited to this. For example, as shown in FIGS.
Even in the case of a vertical blade type milling cutter in which the chip 22 is mounted in the chip mounting groove 21 of No. 0 so that the side faces the tool circumferential direction, the boss surface 23, the center hole 24, and the chip mounting groove 21 are formed with predetermined accuracy. A similar effect can be obtained by forming a hardened layer by nitriding after processing. In addition, even in such a vertical blade milling machine, the corners of the wall surface of the chip mounting groove 21 are rounded to form a minute curved surface 25, or the corners are chamfered to prevent crack growth. Of course, you can.

In each of the above embodiments, the present invention is applied to a face mill. However, as shown in FIG. 9 and FIG. Naturally, the present invention can also be applied to a ball end mill equipped with chips 33 and 34 having blades 31 and 32. In this case, the surface of the shank portion 35 (range indicated by the dashed-dotted line T in FIG. 9) mounted on the main shaft of the machine tool is generated by nitriding similarly to the boss surface and the center hole in the case of milling. It is preferable to use a polished surface from which the soft coating has been removed. Further, in addition to these examples, the present invention is applied to various indexable cutting tools.

Incidentally, the above-mentioned tool bodies 1, 20, 3
For example, as shown in FIG. 4 and FIG.
Screw holes 40, 41, and 42 for attaching components such as 2, 33, and 34 and the sheet 4 are formed. Insides of the screw holes 40 to 42 are formed with a nitriding preventing portion in which formation of a hardened layer is prevented. Is preferred. When the nitriding process is performed to the inside of the screw holes 40 to 42, the hardness of the thread is significantly increased and the toughness is lost, and the set screw 5 and the clamp screws 7, 26
This is because the repeated repetition of attachment and detachment may cause the thread to be cracked or chipped at an early stage, and the hardness of the thread may damage the other clamp screw 7, 26 or the like.

Here, as a method of forming the anti-nitriding portions of the screw holes 40 to 42, for example, a method of applying a known anti-nitriding agent into the screw holes can be considered. However, the nitriding agent is in a liquid state, and it is difficult to accurately apply it only to a necessary portion. Therefore, a large application area is increased and an anti-nitridation part is unnecessarily spread, or the nitriding effect is uneven due to uneven coating. There is a possibility that. Further, the nitridation inhibitor may adhere to extra portions of the tool bodies 1, 20, and 30, and a desired hardened layer may not be obtained. Further, the anti-nitriding agent may be left inside the screw holes 40 to 42, and it may be difficult to smoothly rotate the clamp screw 7 and the like.

Therefore, in order to form the above-mentioned nitriding preventing portion,
For example, as shown in FIG.
42 (only screw hole 42 is shown in the figure)
The screw hole 50 is screwed in to seal the screw holes 40 to 42, and in this state, nitriding treatment is performed to form a hardened layer on the surface of the chip mounting groove 21 and the like, and thereafter, as shown in FIG.
It is desirable to follow the method of removing the setscrew 50 from 2. According to this method, since the inside of the screw holes 40 to 42 is securely sealed by the set screw 50, the entry of the nitriding agent such as ammonia gas into the screw holes 40 to 42 is prevented, and the nitridation preventing portion is reliably obtained. In addition, since there is no need to apply an anti-nitriding agent, there is no danger that an anti-nitridation portion will be erroneously formed in a portion other than the inside of the screw holes 40 to 42, and furthermore, the application of the anti-nitriding agent may cause a non-uniform nitriding effect. This is because uniformity cannot occur.

In the examples shown in FIGS. 11 to 12, the material of the set screw 50 is not specified.
When the set screw 50 is formed of a non-nitridable material such as brass, the set screw 50 is not nitrided at the time of the nitriding process, so that the set screw 50 does not deteriorate before and after the nitriding process. The cost required for the nitriding treatment can be reduced. In this case, the material of the set screw 50 is 500 ° C., which is the heating temperature during nitriding.
Of course, it is necessary to select a non-nitridable material that can withstand a high temperature of 600 ° C. Further, even when the set screw 50 is formed of a material which is easily nitrided, such as steel, the surface of the set screw is nickel-plated, or an anti-nitridation agent is applied to form the anti-nitridation layer in advance, thereby stopping the set screw 50. The reuse of the set screw 50 can be realized by preventing the screw 50 from nitriding.

Further, in the examples shown in FIGS. 11 and 12, the set screw 50 is used as a snoop. However, the present invention is not limited to this. For example, as shown in FIG.
In addition, a headed bolt such as a hexagon bolt may be used. In this case, since the end surface 51a of the head of the bolt 51 is in close contact with the bottom surface 21a of the chip mounting groove 21, the sealing in the screw hole is further improved, and the nitriding prevention effect can be further enhanced. However, FIG.
In the example shown in FIG. 3, since the nitriding agent does not touch the portion of the bottom surface 21a of the chip mounting groove 21 which is in close contact with the bolt head end surface 51a, the nitridation preventing portion is formed not only inside the screw holes 40 to 42 but also at the mouth thereof. There is an inconvenience of slightly expanding around the part.

In order to prevent the nitridation preventing portion from expanding while improving the airtightness inside the screw holes 40 to 42, for example, as shown in FIG.
(Shown only) at the mouth portion of a flat head screw 54 having a tapered surface 52 whose diameter increases toward the opening end of the screw hole 40 to 42 and a tapered surface 53 which can be tightly attached to the tapered surface 52 as a snoop. It is desirable to use According to this example,
When the tapered surface 53 of the flat head screw 54 and the tapered surface 52 of the screw holes 40 to 42 are in close contact with each other, the sealing performance inside the screw holes 40 to 42 is improved, and a high nitridation prevention effect is obtained. Since the bottom surface 21a of the screw 21 does not come into close contact with the flathead screw 54 and the periphery of the screw holes 40 to 42 is opened, the nitriding agent such as ammonia gas reaches the limit around the mouth of the screw holes 40 to 42 and prevents the nitriding. This has the effect of preventing unnecessary enlargement.

(Experimental Example) Here, the tool body of the face milling machine shown in FIGS. 1 to 4 was actually manufactured and its hardness was measured. The result is shown in FIG. At this time, a gas nitriding method using ammonia gas was used as the nitriding method, and SCM440 was selected as the material of the tool body. The nitriding time was changed in three stages of 20 hours, 30 hours, and 40 hours. As is clear from FIG. 15, after the maximum hardness was obtained in the range of 0.05 mm from the tool surface regardless of the length of the nitriding treatment time, the hardness decreased as it progressed to the inside of the tool, and the hardness decreased by 0.4 mm from the tool surface. The difference in hardness between the inside of the tool and the tool at the position has disappeared. Therefore, in order to ensure a hardened layer on the tool surface layer portion, it is preferable that the thickness be 0.1 mm or more, and even if the nitriding time is extended, it is 0.4 mm.
Since it is difficult to obtain the above hardened layer and there is a possibility that only the hardness of the surface layer is unnecessarily increased to cause cracking, it has been found that it is preferable to set the hardened layer to 0.4 mm or less.

[0033]

As described above, according to the cutting tool of the first aspect, the required hardness of the tool main body is secured by the nitriding treatment, but the large distortion such as that of the quenching treatment during the nitriding treatment is obtained. Since it does not occur, there is no need to perform finishing work later, and the number of man-hours for manufacturing the tool body is greatly reduced. In addition, since no large residual stress is generated during the nitriding treatment, there is no fear that accuracy is lost due to release of the subsequent stress. Furthermore, since the accuracy of the chip mounting groove is maintained, the runout accuracy is not impaired, and as a result, an excellent effect of providing a highly durable, highly accurate and inexpensive cutting tool can be obtained. In addition, the mounting that serves as the mounting reference for the tool body
Since the soft coating has been removed from the part,
Prevents deformation of the mounting part when mounting to a machine, and mounting accuracy
Reproducibility can be secured.

According to the cutting tool of the second aspect,
Unnecessary increase in internal hardness of the screw hole is prevented,
Cracks and chipping of the screw holes are prevented, and
Damage to hand bolts is also prevented. Claims 3 and 4
According to the described cutting tool, the manufacturing cost is greatly reduced, especially in the case of a tool body such as a milling tool having a large number of chip mounting grooves. Furthermore, according to the cutting tool of the fifth and sixth aspects , stress concentration on the corners of the chip mounting groove during nitriding is alleviated, thereby preventing cracks in the hardened layer and providing a high quality hardened layer. Is done. In addition, according to the cutting tools of the seventh and eighth aspects, since the hardened layer can be prevented from cracking while sufficiently securing the hardness of the hardened layer, the quality of the hardened layer can be further improved.

[0035] Then, according to the manufacturing method of a cutting tool according to claim 9, wherein, while the homogeneous nitriding preventing portion internal threaded hole is securely sealed can be easily obtained by Umasen erroneous besides internal threaded hole Thus, there is no danger that a nitridation preventing portion is formed. Further, since according to the method of manufacturing a cutting tool according to claim 10, 11 wherein repeatedly Umasen available can greatly reduce the cost required nitriding, further claims
According to the cutting tool described in 12 , the sealing property in the screw hole can be further improved to obtain a more uniform nitridation preventing portion, and the nitriding agent can surely reach the vicinity of the mouth portion of the screw hole to prevent the nitriding portion. Unnecessary expansion can be prevented.

[Brief description of the drawings]

FIG. 1 is a sectional view in a tool axis direction according to an embodiment of the present invention.

FIG. 2 is a view as seen from an arrow II in FIG. 1;

FIG. 3 is a view as seen from the direction of arrow III in FIG. 1;

FIG. 4 is a view from arrow IV in FIG. 3;

FIG. 5 is a sectional view in a tool axis direction according to another embodiment of the present invention.

FIG. 6 is a view from arrow VI in FIG. 5;

FIG. 7 is a view as seen from the direction of arrow VII in FIG. 5;

8 is a view as seen from the direction of arrow VIII in FIG. 7;

FIG. 9 is a side view of a tool according to still another embodiment of the present invention.

FIG. 10 is a view as seen from the X direction in FIG. 9;

FIG. 11 is a cross-sectional view of a chip mounting groove in one embodiment of the method for manufacturing a cutting tool according to the present invention.

FIG. 12 is a diagram showing a state in which the scrutiny is removed from the state shown in FIG. 11;

FIG. 13 is a diagram showing a modification of the example shown in FIG. 11;

FIG. 14 is a diagram showing still another modification of the example shown in FIG. 11;

FIG. 15 is a diagram showing the relationship between the depth of nitriding and hardness.

[Explanation of symbols]

 1, 20, 30 Tool body 2a, 21, 31 Chip mounting groove 6, 22, 33, 34 Chip 9, 24 Center hole (mounting part) 10, 23 Boss surface (mounting part) 35 Shank part (mounting part) 40, 41, 42 Screw hole 50 Set screw (Snoop) 51 Hexagon socket head bolt (Snoop) 52 Tapered surface of screw hole 53 Tapered surface of countersunk screw 54 Countersunk screw (Snoop)

────────────────────────────────────────────────── ─── Continuation of the front page (56) References JP-A-61-274808 (JP, A) JP-A-61-288914 (JP, A) JP-A-52-58024 (JP, A) (58) Field (Int.Cl. ⁷ , DB name) B23C 5/20 B23C 5/10 B23P 15/28 B23P 15/34

Claims (12)

(57) [Claims] 1. A cutting tool having a plurality of chip mounting grooves formed in a tool main body having a mounting portion to a machine tool, and a throw-away chip being removably mounted in the chip mounting grooves. A hardened layer formed by nitriding is formed on the part, and the hardened layer is formed on the mounting part of the tool body.
The surface of the hardened layer is soft coated by nitriding.
A cutting tool having a polished surface from which a film has been removed . 2. The indexable chip is attached to the tool body.
Screw holes for attaching other parts
Prevents the formation of a hardened layer due to nitriding inside this screw hole
Claims characterized in that it is a nitriding prevention part
The cutting tool according to 1 . Surface wherein it said chip said hardened layer formed in the mounting groove is claim 1 or claim, characterized in that there is a skin surface not subjected to finishing after the nitriding treatment
3. The cutting tool according to 2 . 4. A cutting tool in which a plurality of chip mounting grooves are formed in a tool body having a mounting portion to a machine tool, and a throw-away chip is removably mounted in these chip mounting grooves. A hardened layer is formed on the portion by a nitriding process, and a surface of the hardened layer formed in the chip mounting groove is a bare surface which is not subjected to a finishing process after the nitriding process. Cutting tools. 5. The method according to claim 1, wherein the corner of the chip mounting groove is chamfered or rounded.
The cutting tool according to any one of claims 1 to 4 . 6. A cutting tool in which a plurality of chip mounting grooves are formed in a tool body having a mounting portion to a machine tool, and a throw-away chip is removably mounted in these chip mounting grooves. A cutting tool, wherein a hardened layer is formed on a portion by a nitriding process, and a corner portion of the chip mounting groove is chamfered or rounded. Hardness of 7. The said cured layer of said tool body, to any one of claims 1 to 6, characterized in that it is set to HV500 or more at a position 0.1mm from the surface of the tool body The described cutting tool. 8. A cutting tool in which a plurality of chip mounting grooves are formed in a tool body having a mounting portion to a machine tool, and a throw-away chip is removably mounted in these chip mounting grooves. A hardened layer is formed on the surface layer by nitriding, and the hardness of the hardened layer of the tool body is HV at a position of 0.1 mm from the surface of the tool body.
A cutting tool characterized by being set to 500 or more. 9. A tool body is subjected to nitriding treatment after mounting a knurl in a screw hole formed in the tool body to form a hardened layer on a surface layer portion of the tool body, and thereafter, the knurl is removed. 3. The method for manufacturing a cutting tool according to claim 2, wherein: 10. A method for manufacturing a cutting tool according to claim 9, wherein a non-nitridable material is used for said embedment. 11. The manufacturing of a cutting tool according to claim 9 , wherein after forming a nitridation preventing layer on the surface of the stub, the snip is attached to a screw hole of the tool body to perform a nitriding treatment. Method. 12. A tapered surface which increases in diameter toward the opening end of the screw hole at the mouth portion of the screw hole of the tool body, and has a tapered surface which can be in close contact with the tapered surface on the stub. The method for manufacturing a cutting tool according to any one of claims 9 to 11 , wherein a countersunk screw is used.