JP2008006538A - Throw-away cutting tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a small-diameter throw-away cutting tool exerting high adhesion between a throw-away tip and a tip mounting seat face, facilitating the attachment/detachment of the throw-away tip, and having superior tool rigidity and machining accuracy. <P>SOLUTION: This throw-away cutting tool formed by detachably mounting the throw-away tip 40 on the tool body 10 by a screw-on method is characterized in that, a screw hole 11 is opened inclined in the elongation direction of the fitting length L of a fastening screw 30 relative to an axis C1 perpendicular to the base 21 of the tip mounting seat, the shape of the vertical cross section in the head part 31 of the fastening screw 30 is a projecting arc shape, and the fitting hole 41 is formed into a recessed arc shape fitted with the head part 31 of the fastening screw 30. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a throw-away cutting tool in which a throw-away tip is detachably attached to a tool body, and in particular, a tightening screw is screwed into a tip mounting seat of a tool body through a mounting hole of the throw-away tip. The present invention relates to a screw-on type throw-away cutting tool that fixes a throw-away tip to a tool body.

As a throw-away tip clamping method, a tightening screw is screwed into a screw hole formed in the bottom surface of the tip mounting seat of the tool body through a mounting hole provided in the throw-away tip, thereby throwing away the throw-away tip. There is a screw-on system that fixes the insert to the tool body.
Conventionally, in a throw-away cutting tool in which a throw-away tip is detachably mounted by this screw-on method, a screw hole is drilled perpendicularly to the bottom surface of the tip mounting seat, and the center axis of the screw hole Is formed so as to be decentered with respect to the center axis of the mounting hole of the throw-away tip, and when the tightening screw is screwed into the screw hole through the mounting hole, the throw-away tip is attached to the tip mounting seat surface. It was pressed and fixed to the tool body (see FIG. 3).
In such a clamp mechanism, in the case of a throw-away type cutting tool with a small tool diameter, the length of the screw portion of the tightening screw cannot be secured sufficiently, and the length of the fit between the screw hole and the screw portion. Is not sufficient, the clamping force is inferior, and the tightening screw may be loosened due to vibration during the cutting process. As a result, there is a risk of cutting failure due to the displacement of the throwaway tip, damage to the throwaway tip, breakage of the tightening screw, and the like. Therefore, when a highly accurate small-diameter cutting tool is required, an expensive peeler, peeler, peeler, etc., in which the blade and the body or shank are made of the same material must be used. did not become.
In order to solve this problem, a throw-away cutting tool has been proposed in which a screw hole is drilled from the bottom wall of the tip mounting seat into the tip of the tool body in the direction of increasing the thickness of the cross section. (For example, refer to Patent Document 1).
JP-A-7-164213 (FIG. 1)

However, in the invention of Patent Document 1, the tip of the clamp screw is attached to the tip by tilting and receiving the head of the clamp screw on the receiving seat portion formed at the opening end of the through-hole of the throw-away tip. It is configured to clamp on the seat. According to such a configuration, by inserting the clamp screw into the screw hole, the receiving seat surface of the through-hole of the throw-away tip is pulled into the side wall side while being pressed against the bottom wall of the tip mounting seat by the head of the clamp screw. Thus, the engagement surface between the head of the clamp screw and the receiving seat surface comes into a contact state on one side. Therefore, since the throw-away tip comes into contact with the tip mounting seat with the head of the clamp screw elastically deformed from this one-contact state, a large bending stress acts on the clamp screw and the clamp screw breaks. There was a problem to do. Furthermore, when the head of the clamp screw comes into contact with one side, the throw-away tip cannot be pressed uniformly against the bottom wall of the mounting seat, and in particular, the adhesion of the lower surface on the cutting edge side that performs the cutting action is inadequate. Therefore, there is a problem that the throw-away tip is lifted along with the cutting process, and chatter vibration is induced to damage the cutting edge, resulting in poor machining accuracy.
In general, the shape of the longitudinal section of the head of the clamp screw is a tapered shape that is linearly inclined toward the shaft (see FIG. 1 in Patent Document 1), and is provided on the screw head. The depth of the wrench hole is shallow from the viewpoint of securing the strength of the screw head. As described above, when the depth of the spanner hole is small, the spanner is difficult to be applied, it is difficult to tighten the screw, and there is a problem that the operability at the time of attaching / detaching the throw-away tip is poor. Further, when the tightening torque is increased, the hole for spanner is crushed, and there is a problem that the screw cannot be removed and the throw-away tip cannot be replaced. Moreover, there also existed a problem that the spanner tip part will be damaged.

  The present invention has been made to solve the above-described problem, and is excellent in clamping force of the throw-away tip against the tool body, has good adhesion between the throw-away tip and the tip mounting seat surface, and easily throw-away tip. It is an object of the present invention to provide a small-diameter throw-away type cutting tool with excellent tool rigidity and machining accuracy.

In order to solve the above problems, the throw-away cutting tool of the present invention employs the following means.
The present invention provides a tool main body having a tip mounting seat with a screw hole formed in the bottom surface, a tightening screw screwed into the screw hole of the tool main body, and screwing the tightening screw into the screw hole. A throw-away type cutting tool having a throw-away tip with a mounting hole penetratingly attached to the tip mounting seat in a detachable manner, wherein the screw hole is tightened against an axis perpendicular to the bottom surface of the tip mounting seat The screw fitting length is formed so as to be inclined and drilled in the extending direction, the vertical cross-sectional shape of the head of the tightening screw is a convex arc shape, and the mounting hole is connected to the head of the tightening screw. It is formed in the concave arc shape to fit.

  According to the present invention, the screw hole is formed so as to be inclined and drilled in the extending direction of the fitting length of the fastening screw with respect to the axis perpendicular to the bottom surface of the chip mounting seat. Even with a small throw-away cutting tool, the fitting length of the tightening screw can be secured sufficiently, so it has excellent clamping force and can prevent the tightening screw from loosening due to vibration during cutting. It is possible to prevent cutting failure due to the displacement of the throwaway tip, breakage of the throwaway tip, breakage of the tightening screw, and the like. Thus, the fact that the screw hole is inclined in the direction in which the fitting length of the tightening screw is extended means that the screw hole is inclined in the direction of increasing the thickness of the cross section in the vicinity of the screw hole of the tool body. This means that the rigidity of the tool can be maintained by ensuring the thickness of the tool body.

  In addition, the shape of the longitudinal section of the head of the tightening screw is a convex arc shape, and the mounting hole is formed in a concave arc shape that fits with the head of the tightening screw. Even if it is provided, the head of the tightening screw and the engaging surface of the mounting hole are in contact with each other and come into uniform contact with each other, so that a stable fixed state is obtained. Therefore, excessive bending stress does not act on the tightening screw, and the tightening screw is not broken. Since the head of the tightening screw comes into contact with the entire surface in this way, the throw-away tip can be uniformly pressed against the bottom surface of the tip mounting seat, and the tip is mounted on the lower surface of the throw-away tip. Since the adhesiveness with the seating surface is improved, chatter vibrations and the like caused by the rising of the chip due to cutting can be suppressed, and damage to the blade edge can be prevented. And since it becomes difficult to generate | occur | produce the damage of a blade part, a broken screw, etc., the throwaway type cutting tool excellent in processing precision, such as a tool life, a dimensional tolerance, and finishing surface roughness, can be provided.

  Furthermore, since the shape of the longitudinal section of the head of the tightening screw is a convex arc, even a small tightening screw used in a throw-away cutting tool with a small tool diameter has a spanner hole. It is possible to ensure a sufficient depth. Therefore, the depth of the spanner hook hole can be deepened compared to the conventional head with a longitudinal cross-sectional shape, so it is easy to wrench and tighten the screw easily. Excellent operability when attaching and detaching. In addition, since the depth of the spanner hole can be secured sufficiently, the spanner hole may be crushed or the end of the spanner may be damaged even if the tightening torque is increased by increasing the spanner size. There is no trouble in the attachment and detachment of the chip.

  According to the throw-away cutting tool of the present invention, even a throw-away cutting tool with a small tool diameter is excellent in the clamping force of the throw-away tip against the tool body and the adhesion between the throw-away tip and the tip mounting seat surface. For this reason, it is difficult to cause damage to the blade portion, breakage of the screw, and the like due to cutting, and the tool life and machining accuracy are improved. In addition, even when a small tightening screw is used in a throw-away cutting tool with a small tool diameter, the operability at the time of attaching / detaching the throw-away tip is excellent.

Hereinafter, an embodiment of the throw-away cutting tool of the present invention will be described with reference to the drawings.
FIG. 1 is a front view of a throw-away end mill showing an embodiment of a throw-away cutting tool of the present invention, and FIG. 2 is an enlarged cross-sectional view taken along a plane along line AA in FIG.
As shown in FIGS. 1 and 2, the main body of the throw-away end mill 100 according to the present embodiment has a substantially cylindrical shape, and a tip mounting seat 20 is formed on the side portion at the tip of the tool main body 10. Has been. The tip mounting seat 20 includes a bottom surface 21 that forms a flat surface parallel to the central axis of the throwaway end mill 100 and a side surface 22 that intersects the bottom surface 21, and a screw hole 11 is formed in the bottom surface 21. A tightening screw 30 including a head portion 31 in which a spanner hooking hole 33 is formed and a screw portion 32 screwed into the screw hole 11 is screwed into the screw hole 11.
On the other hand, the throw-away tip 40 attached to the throw-away end mill 100 has a substantially parallelogram flat plate shape made of cemented carbide, cermet, ceramics, etc., and has a cutting edge formed on the side ridge and attached. A hole 41 is formed through.
Therefore, after the throw-away tip 40 is seated on the tip mounting seat 20 of the tool body 10, the fastening screw 30 is screwed into the screw hole 11 of the tool body 10 via the mounting hole 40. The head 31 is locked to the attachment hole 41 so that the head 31 is detachably attached to the throw-away end mill.
Then, the throw-away end mill 100 to which the throw-away tip 40 is attached is used by moving the end mill main body 100 while bringing it into contact with the workpiece.

  In this way, by inserting the tightening screw 30 into the screw hole 11 formed in the tip mounting seat 20 of the tool body 10 through the mounting hole 41 provided in the throw-away tip 40, the throw-away tip 40 is inserted. A clamp method for fixing the tool to the tool body 10 is called a screw-on method. When such a screw-on method is employed, the throw-away tip is attached to the tool body with a single screw, so that the structure is simple and can be manufactured at low cost and the tool management is easy. In addition, since it is compact in design, it can be used even with a cylindrical end mill having a small tool diameter in which a space for attaching the throw-away tip is limited.

Further, as shown in FIG. 2, the screw hole 11 has a predetermined length in the direction in which the fitting length L of the fastening screw extends with respect to the axis C1 perpendicular to the bottom surface 21 of the chip mounting seat 20, as indicated by the center line C2. It is formed so as to be inclined at an angle α.
The throw-away tip 40 is pressed against the bottom surface 21 of the tip mounting seat 20 and the side surface when the head 31 of the fastening screw screwed into the screw hole 11 is inclined and pressed against the mounting hole 41. It is fixed so that it may be drawn into 22.

  According to such a configuration, even in the case of a cylindrical end mill having a small tool diameter, the fitting length L of the fastening screw, that is, the axis of the portion where the screw portion 32 and the screw hole 11 are in contact with each other and fitted together Since the length L in the direction can be sufficiently secured, the clamping force is excellent, and the tightening screw 30 can be prevented from loosening due to vibration during cutting. As a result, problems such as cutting defects due to the displacement of the throw-away tip 40, damage to the throw-away tip 40, breakage of the tightening screw 30, and the like do not occur. At the same time, since the screw hole 11 is formed so as to be inclined and drilled in the thickness increasing direction in the cross section in the vicinity of the screw hole of the tool body 10, the thickness of the tool body 10 is ensured. Thus, the tool rigidity can be maintained.

  Further, the shape of the longitudinal section of the head 31 of the fastening screw is formed in a convex arc shape, and the mounting hole 41 of the throw-away tip is formed in a concave arc shape that fits with the head 31 of the fastening screw. ing.

  According to such a configuration, the engaging surface of the head 31 of the tightening screw and the mounting hole 41 is brought into a single-sided contact state like the conventional throw-on type cutting tool by the clamp-on method, and the head 31 is elastically deformed. (See FIG. 3 and FIG. 1 in Patent Document 1), the throw-away tip 40 is brought into contact with the entire contact surface of the head 31 and the mounting hole 41 so as to be in uniform contact with each other. Since it is fixed to the chip mounting seat 20, the pressing force is dispersed and a stable fixed state is obtained. Therefore, an excessive bending stress does not act on the fastening screw 30 and the fastening screw is not broken. And since the engaging surface of the head 31 and the mounting hole 41 is in the entire contact state, the throw-away tip 40 can be uniformly pressed against the bottom surface 21 of the tip mounting seat 20, and the throw-away tip Adhesion with the chip mounting seat surface on the lower surface on the cutting edge side is improved. For this reason, the tip does not float with cutting, and chatter vibration can be suppressed, so that the tip of the throw-away tip can be prevented from being damaged. Therefore, it becomes difficult to cause tool damage such as breakage of the tightening screw and chipping of the cutting edge, and therefore it is possible to provide a throw-away type cutting tool having excellent processing accuracy such as tool life, dimensional tolerance, and finished surface roughness. .

  Further, since the shape of the longitudinal section of the head portion 31 is a convex arc shape, the depth of the spanner hole 33 can be obtained even with a small tightening screw used for a cylindrical end mill or the like having a small tool diameter. D can be sufficiently secured. Therefore, the depth D of the spanner-hanging hole 33 is made deeper than that of a conventional taper in which the shape of the longitudinal section of the head is linearly inclined toward the shaft side (see FIG. 3). Therefore, it is easy to apply a wrench, and the screw can be easily tightened. Even if the tightening torque is increased by increasing the wrench size or the like, the wrench mounting hole is not crushed or the wrench tip is not damaged, and the attachment / detachment of the chip is not hindered.

  In the above-described embodiment, the throw-away end mill 100 has been described as an example of the throw-away cutting tool according to the present invention, but the present invention is not limited thereto, and the throw-away tool adopting a screw-on method, It can be applied to various cutting tools such as a throw-away drill and a throw-away mill. In the above-described embodiment, the throwaway tip 40 having a substantially parallelogram flat plate shape is used. Instead, a substantially polygonal shape such as a triangle or a rhombus, or a circular flat plate throwaway tip is used. Either a negative chip or a positive chip may be used. Further, in FIG. 1, a two-blade end mill provided with two cutting edges is illustrated as an example, but instead of this, a single-blade end mill or the like may be used, and the number of cutting edges is limited to the above-described embodiment. It is not something.

1 is a front view of a throw-away end mill showing an embodiment of a throw-away cutting tool of the present invention. It is the cross-sectional enlarged view cut | disconnected by the plane in alignment with the AA of FIG. It is sectional drawing explaining the chip | tip attachment state of the conventional throwaway type cutting tool.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Tool body 11 Screw hole 20 Tip mounting seat 21 Bottom face 30 Clamping screw 31 Head 40 Throw away tip 41 Mounting hole L Fit length 100 Throw away end mill

Claims (1)

A tool body including a tip mounting seat with a screw hole drilled in the bottom;
A tightening screw to be screwed into the screw hole of the tool body;
A throw-away cutting tool having a throw-away tip with a mounting hole penetratingly attached to the tip mounting seat by screwing the tightening screw into the screw hole;
The screw hole is formed so as to be inclined and drilled in an extending direction of the fitting length of the fastening screw with respect to an axis perpendicular to the bottom surface of the chip mounting seat,
The shape of the longitudinal section at the head of the tightening screw is a convex arc shape,
The throw-away cutting tool, wherein the mounting hole is formed in a concave arc shape that fits with a head of the tightening screw.

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