JP2001277032A - Shrink-fitting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To fix a working tip to a tool body with high fitting rigidity when the tool body is integrally joined with the working tip by shrink-fitting. SOLUTION: When a fitting shaft 30 provided on the working tip 14 is integrally shrink-fitted to a fitting hole 24 provided in a columnar protruded portion 18, a cylindrical member 32 is arranged on an outer circumferential side of the columnar protruded portion 18, and the columnar protruded portion 18 is cooled and shrunk in the shrink-fitting. Since the cylindrical member 32 is held in the axial direction between the body 12 and the working tip 14, the working tip 14 is fixed to the body 12 with high fitting rigidity.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a shrink fitting tool in which a processing chip provided with a predetermined processing portion is integrally bonded to a body by shrink fitting.

[0002]

2. Description of the Related Art A joining tool used by integrally forming a shaft-shaped body and a machined chip provided with a machined portion such as a cutting edge, and integrally joining them with screws, brazing, a collet, or the like. It has been known. An end mill described in JP-A-5-96415 or JP-A-4-256512 is one example. According to such a joining tool, only a machining tip is made of an expensive material such as a cemented carbide. Thereby, the tool cost can be reduced as a whole. Further, in the case of a screw or a collet, if a processing portion such as a cutting edge is worn or chipped, only the processing tip needs to be replaced, and the body can be reused.

[0003]

However, in the case of brazing, it is difficult to reuse the body. In the case of screw connection, the screw may be loosened, and when the processing tip is made of a hard material such as a cemented carbide, etc. The screw processing is troublesome.
In the case of a collet, the structure is complicated and expensive, and it is difficult to apply the collet to a small-diameter tool.

On the other hand, as shown in FIG.
0 and a machining tip 104
It is conceivable that a fitting shaft 106 is provided on the base and the fitting hole 102 and the fitting shaft 106 are integrally joined by shrink fitting. According to such shrink fitting, since the body 100 and the processing chip 104 can be easily separated by heating, the body 100 can be reused and the body 100 can be commonly used for a plurality of types of processing chips, and the overall cost is reduced. Moreover, complicated processing such as screws is not required, but sufficient surface pressure (adhesion force) cannot be obtained between the end face 108 of the body 100 and the processing chip 104, and the processing chip 10
There was a possibility that machining rigidity was impaired due to the low mounting rigidity of No. 4. In FIG. 3, processing parts such as cutting edges provided on the processing tip 104 are omitted.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a case in which a body and a processing chip are joined together by shrink-fitting so that the processing chip has a high mounting rigidity. To be fixed to

[0006]

Means for Solving the Problems To achieve the above object, a first invention comprises (a) a body provided with a fitting hole;
(b) a chip body provided with a predetermined processed portion, and a fitting shaft that stands on the chip body and is fitted into the fitting hole, and the fitting hole and the fitting shaft (C) a column-shaped projection is erected on the body, and an opening is formed in a tip end surface of the column-shaped projection. (D) a cylindrical shape is provided on the outer peripheral side of the columnar protrusion, and the columnar protrusion cools and shrinks during the shrink fitting. A cylindrical member that is axially pressed between the body and the chip body of the processing chip and is integrally fixed.

According to a second aspect of the present invention, there are provided (a) a shaft-shaped body having a fitting hole provided on a center line thereof, (b) a chip body provided with a predetermined processed portion, and a standing body on the center line of the chip body. And a processing tip that is integrally joined to the body by shrink fitting the fitting hole and the fitting shaft. (C) a shrink-fit joining tool that performs predetermined machining by the machining unit by being rotationally driven around an axis; (d) the body includes:
While the columnar projection has a stepped shape concentrically erected, the fitting hole is provided so as to open at the tip end surface of the columnar projection, while (e) a cylindrical shape And concentrically disposed on the outer peripheral side of the columnar protrusion, and in the axial direction between the body and the chip body of the processing chip due to cooling shrinkage of the columnar protrusion during the shrink fitting. It is characterized by comprising a tubular member that is pinched and integrally fixed.

According to a third invention, in the shrink fitting tool according to the first invention or the second invention, the fitting hole and the fitting shaft are brought into close contact with each other at least in a joined state by shrink fitting, and the fitting shaft is provided. Characterized in that it is provided with a tapered portion having a larger diameter as it goes toward the distal end side.

[0009]

According to the shrink fitting tool of the first invention,
Since the processing chip is integrally joined to the body by shrink fitting of the fitting hole and the fitting shaft, it is possible to separate the body and the processing chip by heating. The body can be commonly used for various types of processing chips, and troublesome processing such as screws is not necessarily required, so that it is simple and inexpensive.

In addition, a column-shaped projection is provided on the body to form a fitting hole, and a cylindrical member is disposed on the outer peripheral side of the column-shaped projection, so that the column-shaped projection is formed when shrink fitting is performed. Since the cooling shrinkage of the part causes the body and the chip body of the processing chip to be axially pressed and fixed integrally, the mounting rigidity of the processing chip to the body increases and the processing accuracy increases Is improved. Since the cylindrical member does not need to be heated when the body and the processing chip are joined by shrink fitting, the processing chip is integrally fixed to the tip of the columnar projection by cooling and can be shrunk in the axial direction. The dimensions of the cylindrical member do not change, and the processing chip is pulled by the body due to the contraction of the columnar projection, so that the cylindrical member is pressed between the processing chip and the body.

The shrink-fit joining tool of the second invention performs predetermined machining by a machining portion provided on a machining tip by being rotationally driven about an axis. This corresponds to the embodiment, and the same operation and effect as the first invention are obtained.

In the third aspect, the fitting hole and the fitting shaft are brought into close contact with each other at least in a joined state by shrink-fitting, and have a tapered portion having a larger diameter toward the distal end side of the fitting shaft. Therefore, when the fitting hole provided in the body is cooled and contracted, a pulling force in a direction of pulling the fitting shaft into the fitting hole is generated due to the action of the tapered surface of the tapered portion, and the columnar protrusion contracts in the axial direction. When the cylindrical member is squeezed, the reaction force prevents the fitting shaft of the processing chip from coming out of the fitting hole, and the cylindrical member is securely squeezed to further increase the bonding strength between the processing chip and the body. improves.

[0013]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The shrink-fit joining tool according to the present invention is provided with a cutting edge such as a bottom blade or an outer peripheral blade as the processing portion, and is driven to rotate around an axis to perform cutting. And the like, but can be applied to various tools such as a rotary grinding tool having a grinding portion such as a grindstone as a processing portion and a cutting tool disposed at a fixed position and performing a turning process. A plurality of processing chips may be integrally fixed to a single body by shrink fitting.

In the case of an end mill, the processing chip is suitably applied to a ball end mill having a ball blade provided on a hemispherical head (tip body), for example. May be provided.

The joining method of such a shrink fit joining tool includes, for example, (a) a heating step of expanding a fitting hole by heating and expanding a columnar projection of a body; and (b) a heating step of expanding the columnar projection. A cylindrical member is arranged on the outer peripheral side of the cylindrical projection, and a fitting step of fitting a fitting shaft of the processing chip into a fitting hole of the columnar projection, and (c) cooling and shrinking the columnar projection. And a cooling step of integrally joining the fitting hole of the columnar projection and the fitting shaft, and pressing the cylindrical member between the body and the chip body of the processing chip. In the cooling step, it is desirable to press the processing tip and the body so as to approach each other with the tubular member interposed therebetween.

The diameter difference (tightening margin) between the fitting shaft and the fitting hole at room temperature before joining is determined by the material and thermal expansion coefficient of the body and the processing tip so that sufficient joining strength can be obtained by shrink fitting. For example, when the inside diameter (diameter) of the fitting hole is increased by about 30 μm by heating for shrink fitting, the diameter of the fitting shaft is 10 to 20 μm larger than that of the fitting hole at room temperature. It is desirable to make it large.
In the case where the tapered portion is provided as in the third invention, the diameter difference between the large-diameter portion and the small-diameter portion is set at least so that the fitting shaft can be fitted into the fitting hole during heating. It is necessary to make the value smaller than the value obtained by subtracting the interference from the enlarged diameter of the hole, and, for example, 5 to 20 μm depending on the size of the interference so as to obtain a pull-out preventing action (tensile force) due to the taper at the time of engagement. It is desirable to set within a range of about (10 μm or less if the interference is 20 μm).

The materials of the body and the machining tip are appropriately set. For example, tool steel such as high-speed tool steel and steel such as stainless steel are suitably used for the body, and carbide is used for the machining tip for cutting. A hard material such as an alloy is preferably used. In addition, in order to facilitate removal of the processing chip (reheating to expand the fitting hole in the body and pull out the fitting shaft), the processing chip is made of a material with a sufficiently smaller coefficient of thermal expansion than the body. It is desirable that

The cylindrical member is made of a tool steel such as a high-speed tool steel, a steel such as a stainless steel, or a hard material such as a cemented carbide, etc. Although it is possible to adopt a member made of various materials that can obtain rigidity, when heating and separating the fitting portion between the body and the processing tip, a cylindrical member sandwiched between them is used. Is also heated, so that it is desirable to use a material having a small coefficient of thermal expansion so as not to cause deformation or the like due to expansion due to the heating.

The both end surfaces of the cylindrical member, the end surface of the body against which the end surface is pressed, and the end surface of the chip body of the processing tip are, for example, the center line of the cylindrical member (in the second invention, the center line of the shrink-fit joining tool). Is a flat surface perpendicular to the surface, but may be a tapered surface or an annular stepped surface having a step at a radially intermediate portion, or a predetermined unevenness or groove on the surface, or a positioning surface. Protrusions and recesses may be provided. Both end surfaces of the cylindrical member, the end surface of the body, and the end surface of the chip body of the machined chip are all tapered, or a portion of the end surface of the body and the end surface of the chip body of the machined chip that comes into contact with the end surface of the cylindrical member. If you provide an annular step in the
The cylindrical member can be positioned concentrically.

The cylindrical member or the column-shaped protrusion has, for example, a cylindrical shape or a cylindrical shape having a constant diameter, but has a tapered cylindrical shape whose diameter decreases linearly toward the tip end, ie, toward the processing tip. A member or a columnar protrusion may be employed. In the first invention, the cylindrical members and the columnar projections are not necessarily required to have a cylindrical shape or a columnar shape, but may have a rectangular cylindrical shape or a prismatic shape.

It is desirable that the body and the processing tip are integrally formed. However, in the case of the processing tip, for example, the tip body and the fitting shaft are formed separately and integrated by a joining means such as brazing. Each configuration may be determined as appropriate, for example. The body may adopt various aspects such as a body generally called a shank and a body called a holder. The body may be used by being integrally joined to a holder or the like by joining means such as shrink fitting.

In the third aspect, the fitting shaft and the fitting hole are provided with a tapered portion which is brought into close contact with each other at least in a jointed state by shrink fitting, and which has a larger diameter toward the distal end side of the fitting shaft. For example, a tapered fitting shaft having a larger diameter toward the distal end or a tapered fitting hole having a smaller diameter toward the opening at the distal end is employed. At least one of them may have a tapered portion. If either one has a tapered portion, the tapered action can be obtained by being closely attached at the time of shrink fitting. In implementing the first and second inventions, it is not always necessary to provide a tapered portion, and for example, a cylindrical fitting shaft and a fitting hole having a constant diameter can be adopted.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a partially cutaway front view of a ball end mill 10 which is an example of a shrink-fitting joining tool to which the present invention is applied. This ball end mill 10 is formed by shrink-fitting a shaft-shaped body 12 and a processing chip 14. They are integrally joined. The body 12 is made of high-speed tool steel, and has a cylindrical shank 16 having a constant diameter and a cylindrical protrusion having a diameter smaller than that of the shank 16 provided concentrically at one axial end of the shank 16. The projection 18 has a stepped shape integrally with the portion 18, and a fitting hole 24 having a predetermined depth is provided on the center line from the tip end surface 22 of the columnar projection 18. The tip surface 22 is a flat surface perpendicular to the axis, that is, the center line, and the fitting hole 24 is a circular hole having a constant diameter.

The machining tip 14 is made of a cemented carbide having a higher hardness than the high-speed tool steel forming the body 12 and having excellent cutting edge performance and a small coefficient of thermal expansion.
A chip main body 26 having a hemispherical head, and a fitting shaft erected on the center line of a flat engagement surface 28 perpendicular to an axis which is an end surface of the chip main body 26 opposite to the hemispherical head. 30 are integrally provided. When the fitting shaft 30 is tightly fitted into the fitting hole 24 by shrink fitting, the processing chip 14 is integrally joined to the body 12. The diameter difference (tightening margin) between the fitting shaft 30 and the fitting hole 24 at room temperature before joining is determined by, for example, the fitting hole 24 heated by shrink fitting so as to obtain sufficient joining strength by shrink fitting. In this embodiment, the enlarged dimension of the fitting hole 24 is about 30 μm, and the diameter of the fitting shaft 30 is 10 to 20 μm larger than that of the fitting hole 24 at normal temperature. The size is set to be about large.

In the chip body 26, a ball blade is provided as a machined portion on the hemispherical head, and a columnar portion provided continuously on the hemispherical head is provided on the chip body 26 continuously with the ball blade. An outer peripheral blade is provided, and the cutting process is performed by the cutting edge by being driven to rotate around the axis integrally with the body 12, but none of the cutting edges are omitted in FIG. .

On the other hand, on the outer peripheral side of the columnar projection 18, a cylindrical tubular member 32 is disposed substantially concentrically with the columnar projection 18. The inner diameter of the cylindrical member 32 is slightly larger than the outer diameter of the columnar projection 18, and the outer diameter of the cylindrical member 32 is substantially equal to the outer diameter of the tip body 26 and the shank 16. The length of the cylindrical member 32 is slightly longer than that of the columnar projecting portion 18, and when the fitting shaft 30 and the fitting hole 24 are joined by shrink fitting, the body shrinks due to the cooling shrinkage of the columnar projecting portion 18. 1
The second end face 34 and the engagement surface 28 of the processing tip 14 are axially pressed and integrally fixed. Since the tubular member 32 does not need to be heated when the body 12 and the processing chip 14 are joined by shrink fitting, the processing chip 14 is integrally fixed to the end of the columnar projection 18 by cooling and shrinking of the columnar projection 18. Also, when the columnar projection 18 is contracted in the axial direction, the axial length of the cylindrical member 32 does not change, and the processing tip 14 is pulled toward the body 12 by the contraction of the columnar projection 18. The cylindrical member 32 is pressed between the processing chip 14 and the body 12.

The cylindrical member 32 is made of a cemented carbide having a predetermined strength and a small coefficient of thermal expansion, and both end surfaces are flat surfaces perpendicular to the center line.
Engagement surface 28 and end surface 34 also perpendicular to the center line
And is squeezed well.

The joining between the body 12 and the processing chip 14 by shrink fitting is performed by (a) heating the columnar projection 18 of the body 12 (about 300 ° C. in the present embodiment) to expand it. A heating step of expanding the diameter of the hole 24;
(b) a step of fitting the fitting shaft 30 of the processing tip 14 into the fitting hole 24 after disposing the cylindrical member 32 on the outer peripheral side of the columnar projection 18; The columnar projection 18 is cooled and fitted in a state where the processing chip 14 and the body 12 are pressed in the axial direction so that the cylindrical member 32 is pressed between the engagement surface 28 of the body 14 and the end surface 34 of the body 12. And a cooling step of reducing the diameter of the hole 24 and tightly joining the fitting shaft 30 and the fitting hole 24 together by tight fitting.

In the ball end mill 10, the columnar projection 18 of the body 12 is heated to expand the diameter of the fitting hole 24, so that the fitting shaft 30 of the processing chip 14 is pulled out from the fitting hole 24 and separated. When the cutting edge of the processing tip 14 is worn or chipped, the body 1 can be replaced by replacing the processing tip 14 alone.
2 and the tubular member 32 can be reused. Body 1
2 and the cylindrical member 32 are damaged, it is possible to replace only the damaged part in the same manner and reuse other parts, or to use a plurality of types of processing chips 14 by attaching them to the common body 12. You can also. In the present embodiment, since the processing chip 14 has a smaller coefficient of thermal expansion than the body 12, the fitting shaft 30 of the processing chip 14 can be easily pulled out from the fitting hole 24. When the columnar projection 18 is heated, the cylindrical member 32 disposed on the outer peripheral side is heated first, but since the cylindrical member 32 is made of cemented carbide and has a small coefficient of thermal expansion, There is no danger of deformation or breakage due to excessive force generated by expansion due to the heating.

As described above, in the ball end mill 10 of the present embodiment, the processing tip 14 is integrally joined to the body 12 by shrink fitting of the fitting hole 24 and the fitting shaft 30. Heating body 12 and processing chip 1
4 can be separated, the body 12 and the processing chip 14 can be reused, and the body 12 can be commonly used for a plurality of types of processing chips 14, and complicated processing such as screws is not required. In addition, it is configured at low cost. In addition, a cylindrical member 32 is provided between the body 12 and the processing tip 14, and the columnar projection 18 is cooled and shrunk during shrink fitting, so that the body 12 and the processing tip 14 are formed.
Are fixed in an integrated manner by being pinched in the axial direction between them, the mounting rigidity of the processing chip 14 to the body 12 is increased, and the processing accuracy is improved.

In the above embodiment, the fitting shaft 30 and the fitting hole 24 each have a cylindrical shape having a constant diameter. However, the fitting shaft 40 and the fitting hole 42 shown in FIG. As described above, in the jointed state by shrink fitting, the tapered shape may be brought into close contact with each other, and may have a larger diameter toward the distal end side of the fitting shaft 40. That is, in the state before the joining, the fitting shaft 40 has a tapered shape whose diameter increases toward the distal end side away from the engaging surface 28, and the fitting hole 42 of the columnar projection 18 also has the fitting shaft 42. A taper shape corresponding to the taper shape of No. 40, that is, a taper shape having a larger diameter as it proceeds from the distal end face 22 to the inside, has a similar taper shape even in the joined state of FIG.
In this embodiment, since the processing tip 14 has higher hardness and rigidity than the body 12, the fitting hole 42 is mainly elastically deformed along the fitting shaft 40 in the joined state. Further, the entire fitting range of the fitting shaft 40 and the fitting hole 42 corresponds to a tapered portion.

When the tapered fitting shaft 40 and the fitting hole 42 are employed, the fitting hole 42 is reduced in diameter in the cooling step and is pressed against the outer peripheral surface of the fitting shaft 40, so that the tapered shape is obtained. Since a pulling force is generated in the direction of pulling the fitting shaft 40 into the fitting hole 42 by the action of the tapered surface of the shape, when the columnar projection 18 contracts in the axial direction and presses the cylindrical member 32, Due to the reaction force, the fitting shaft 40 of the processing tip 14 is
2 is prevented, and the cylindrical member 32 is securely pinched so that the joining strength between the processing tip 14 and the body 12 is further improved.

In the embodiment shown in FIG. 2, the fitting shaft 40 and the fitting hole 42 both have a tapered shape before joining, but if at least one of them has a tapered shape, shrink fitting is performed. The same function and effect can be obtained by being closely adhered following the tapered shape at the time of joining.

The embodiments of the present invention have been described in detail with reference to the drawings. However, these embodiments are merely examples, and the present invention is based on the knowledge of those skilled in the art and includes various modifications and improvements. Can be implemented.

[Brief description of the drawings]

FIG. 1 is a partially cutaway front view of a ball end mill which is an example of a shrink fitting tool to which the present invention is applied.

FIG. 2 is a view showing another embodiment of the present invention, and is a front view corresponding to FIG. 1;

FIG. 3 is a sectional view illustrating a comparative example of a ball end mill which is an example of a shrink fitting tool.

[Explanation of symbols]

10: Ball end mill (shrink fit tool) 1
2: Body 14: Processing tip 18: Column-shaped protrusion
24, 42: fitting hole 26: chip body 30, 40: fitting shaft 32: cylindrical member

Claims (3)

[Claims] 1. A body provided with a fitting hole, a chip body provided with a predetermined processed portion, and a fitting shaft erected on the chip body and fitted in the fitting hole. And a machined chip integrally joined to the body by shrink-fitting the fitting hole and the fitting shaft, wherein a shrink-fitting joining tool comprising: The fitting hole is provided so as to be open at the tip end surface of the columnar projection, and is arranged on the outer peripheral side of the columnar projection while forming a cylindrical shape. A shrink fit joining tool, comprising: a tubular member that is axially pressed between the body and the tip body of the processing tip by cooling shrinkage of the protrusion and is integrally fixed. . 2. A shaft-shaped body having a fitting hole provided on a center line thereof; a chip body provided with a predetermined processing portion; and a fitting body which stands on the center line of the chip body and fits in the fitting hole. And a processing tip integrally joined to the body by shrink-fitting of the fitting hole and the fitting shaft, and being driven to rotate about the axis. In the shrink-fit joining tool that performs a predetermined process by the processing portion, the body has a stepped shape in which a columnar columnar protrusion is provided concentrically, and a tip end surface of the columnar protrusion. The fitting hole is provided so as to be open at the same time, while being formed concentrically on the outer peripheral side of the columnar projection with a cylindrical shape, and cooling the columnar projection during the shrink fitting. Due to shrinkage, it is pressed in the axial direction between the body and the chip body of the processing chip. And a tubular member which is a body to fixed, shrink fit joining tool, characterized in that. 3. The fitting hole and the fitting shaft have a tapered portion which is brought into close contact with each other at least in a jointed state by shrink fitting, and which has a larger diameter toward a tip end side of the fitting shaft. The shrink-fit joining tool according to claim 1 or 2, wherein: