JP2001009608A - Shrink fitting type cutting tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To cut with high accuracy without changing the overall length. SOLUTION: A first shaft part 14 of a head part 11 is shrink fitted to a second shaft part 16 of a shank part 12 by means of a cylindrical connecting member. The head part 11 and the shank part 12 are of hard metals, while the connecting member is steel with a high coefficient of thermal expansion. An inside diameter d3 of an inner peripheral face 18a of the connecting member is made smaller than respective outside diameters d1, d2 of the shaft parts 14, 16 to have the size difference as an interference. Although clearances c4, c5 are formed between shoulder parts 15 of the shaft parts 14, 16 and end faces of the connecting member, respectively at ordinary temperature, respective tip faces 14b, 16b of the shaft parts 14, 16 abut on each other, so that the overall length remains unchanged during cutting.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a cutting tool in which a shank portion and a head portion are directly or indirectly tightly fitted.

[0002]

2. Description of the Related Art FIG. 1 shows an example of such a cutting tool.
There is an end mill 1 as shown in FIG. This end mill 1
In this embodiment, the shank portion 2 and the head portion 3 are formed of, for example, an expensive cemented carbide having high rigidity, and the shaft portions 2a, 3a having small diameters, respectively.
Are formed to protrude. And these shaft portions 2a, 3a
The hollow connecting member 4 which is shrink-fitted and fitted with is made of inexpensive steel or the like having a larger coefficient of thermal expansion than a cemented carbide. Then, the connecting member 4 is heated to form the hollow inner peripheral surface 4.
The end mill 1 can be formed by shrink-fitting the shaft portions 2a, 3a of the shank portion 2 and the head portion 3 in the inner peripheral surface 4a in a state where the diameter a is increased. By heating the connecting member 4 and replacing the head portion 3 as necessary, the head portion 3 having different types of cutting blades can be replaced and mounted.

At the time of shrink fitting, at normal temperature, the axial length of the inner peripheral surface 4a of the connecting member 4 is equal to that of the shaft portion 2a of the shank portion 2.
Is larger than the sum of the length of the shaft portion 3a of the head portion 3 and the inner diameter of the inner peripheral surface 4a of the connecting member 4 is set to be larger than that of the shank portion 2.
Of the shaft portion 2a and the shaft portion 3a of the head portion 3 are made smaller than the respective outer diameters, and the difference between the diameters of the two is used as the interference. Then, the shank portions 2 and the shaft portions 2a and 3a of the head portion 3 are inserted into the connecting member 4 heated to about 200 ° C.
The ring-shaped shoulders 2b, 3b at the bases of a, 3a are brought into contact with both end surfaces 4b, 4c of the connecting member 4, respectively. In this state, the distal end surfaces of the shaft portions 2 and 3 are separated by the gap c1 in the inner peripheral surface 4a.
Will be opposed in a state in which is opened. And connecting member 4
Is cooled, the connecting member 4 contracts in the radial direction and
a, 3a can be firmly fixed by the interference. On the other hand, since the connecting member 4 also contracts in its length direction, as shown in FIG. 10 (A), between the two end surfaces 4b, 4c and the shoulders 2b, 3b of the shafts 2a, 3a in the cooled state. Gaps c2 and c3 are generated respectively.

[0004]

When a workpiece is cut by an NC (automatically controlled) machine tool or the like using the end mill 1, the machine tool of the shank portion 2 of the end mill 1 is used. A hole distance to be machined and a cutting dimension are set with the attachment position of 0 as a base point, that is, a base point. When the work material is cut, an end mill 1 that cuts with a cutting blade
And the gap c3 between the head portion 3 and the connecting member 4 and the gap c2 between the shank portion 2 and the connecting member 4 are clogged, and the overall length of the tool body changes to change from L1 to L2. (<L1), resulting in a reduction in machining accuracy. In view of such problems, an object of the present invention is to provide a cutting tool by interference fitting, which does not change its overall length even when a load is applied in an axial direction during cutting.

[0005]

SUMMARY OF THE INVENTION An interference-fitting cutting tool according to the present invention is a cutting tool comprising a head and a shank connected to each other, wherein one of the head and the shank has a shaft and the other has a shaft. The shaft has a hole that fits into the hole and a tightening margin is provided in either the shaft or the hole. The length of the shaft is larger than the depth of the hole, and the tip end surface of the shaft contacts the bottom of the hole. Is characterized by being in contact with. Because the shaft portion and the hole portion are connected and fixed by an interference fit, the front end surface of the shaft portion and the bottom surface of the hole portion are in direct or indirect contact with each other, so that the length (axial line) shrinkage during cooling. Even if there is a gap between the shoulder of the shaft and the outer peripheral surface of the hole, the overall length of the cutting tool does not change when a load is applied in the axial direction of the cutting tool during cutting, and high accuracy Can be cut. Note that the tip surface of the shaft and the bottom surface of the hole may be in direct contact with each other, or may be in contact with each other via another intermediary member. What is necessary is just to be directly transmitted to a shank part through a bottom face. Further, the head portion and the shank portion provided with the shaft portion may have a smaller thermal expansion coefficient than the one provided with the hole portion.

[0006] Further, engagement portions for engaging with each other and preventing relative rotation may be formed on the tip end surface of the shaft portion and the bottom surface of the hole portion, respectively. The positioning of the head portion with respect to the shank portion can be easily performed, and the fitting strength by the interference fit is improved.

The interference-fitting cutting tool according to the present invention is a cutting tool having a head portion and a shank portion connected to each other, wherein the head portion and the shank portion are provided with shaft portions, respectively, and the both shaft portions are brought into contact with each other and connected. Fitting in the hollow part of the member, and a tightening margin is provided in either of the two shaft parts and the connecting member, and the sum of the lengths of both the shaft parts is larger than the length of the hollow part of the connecting member. It is characterized by. Since the distal end surfaces of the two shaft portions are in direct or indirect contact with each other in a state where the both shaft portions and the connecting member are connected and fixed by interference fit, each shaft portion is contracted in the length direction of the connecting member. Even if there is a gap between the shoulder on the outer peripheral side and both end surfaces of the connecting member, the entire length of the cutting tool does not change when a load is applied in the axial direction of the cutting tool at the time of cutting, and cutting can be performed with high precision .
In addition, one shaft part and the other shaft part may directly contact,
The contact may be made via another intermediary member, that is, the load applied to the head portion may be transmitted directly from the end surface of one shaft portion to the shank portion through the end surface of the other shaft portion. Also,
The head part and the shank part may have a smaller coefficient of thermal expansion than the connecting member.

Further, engaging portions for engaging with each other and preventing relative rotation may be formed on the distal end surfaces of the both shaft portions. The positioning of the head portion with respect to the shank portion can be easily performed, and the fitting strength by the interference fit is improved.

[0009]

Embodiments of the present invention will be described below with reference to the accompanying drawings. 1 is a sectional view of a ball end mill according to the first embodiment, FIG. 2 is an exploded sectional view of the ball end mill, and FIG. 3 is an enlarged view of a main part of a shrink fitting portion of the ball end mill shown in FIG. The ball end mill 10 shown in FIGS. 1 and 2 has a head 11 and a shank 12.
Are shrink-fitted by the connecting member 18 to be integrated. The head portion 11 is made of, for example, a cemented carbide, cermet, ceramic, or the like, has a substantially cylindrical shape, and has a tip portion 11a having a substantially hemispherical shape. Tip 1
Although not shown in the drawing, a cutting edge 1a is formed in, for example, a substantially 1/4 arc shape. Base end 11 of head 11
A first shaft portion 14 having a diameter smaller than that of the outer peripheral surface 11c is formed, for example, in a substantially columnar shape.
5 is set. The first shaft portion 14 has a cylindrical peripheral surface 14a.
And a circular tip surface 14b. The first shaft portion 14 is formed coaxially with the central axis O1 of the head portion 11.

The shank portion 12 is made of, for example, cemented carbide, cermet, ceramic, or the like, has a substantially cylindrical shape, and the outer diameter of the outer peripheral surface 12c is substantially the same as the outer diameter of the outer peripheral surface 11c of the head portion 11. I have. For example, a substantially cylindrical second shaft portion 1 having a smaller diameter than the outer peripheral surface 12c is provided at the distal end portion 12a.
6, and a ring-shaped shoulder 17 is formed on the outer peripheral side. The second shaft portion 16 has a cylindrical peripheral surface 16a.
And a circular tip surface 16b. The second shaft portion 16 is formed coaxially with the central axis O2 of the shank portion 12.
Each end face 14b, 16b of the first and second shaft portions 14, 16
Is a plane orthogonal to the axes O1 and O2. The connecting member 18 is formed in a substantially cylindrical shape, and the first shaft portion 14 of the head portion 11 and the second shaft portion 16 of the shank portion 12 are opposed to each other in the hollow portion, and the two shaft portions 14 and 16 are shrink-fitted. I do. The connecting member 18 is made of a material having a higher coefficient of thermal expansion than the head portion 11 and the shank portion 12, for example, steel, and has an inner peripheral surface 18a forming a hollow portion and ring-shaped end surfaces 18 at both axial ends.
b, 18c. The inner diameter of the inner peripheral surface 18a at room temperature is, as shown in FIG.
1, and d3 smaller than d2, and the difference (d1-d
3) and (d2-d3) are interferences by interference fit.

At room temperature, the length S3 of the connecting member 18 along the direction of the central axis O3 is the length of the first shaft portion 14 in the same direction.
With respect to the length S1 of the second shaft portion 16 and the length S2 of the second shaft portion 16,
<S1 + S2. It is assumed that the equation S3 ≦ S1 + S2 is satisfied even when heating for shrink fitting. Therefore, in the shrink-fit state shown in FIG.
Are tightly fitted by the connecting member 18 in a state where they are in contact with each other, and the inner peripheral surface 18a of the connecting member 18 and the two shaft portions 14, 1
6, no space c1 is formed. Moreover, a gap c4 is formed between the shoulder portion 15 of the first shaft portion 14 of the head portion 11 and one end surface 18b of the connecting member 18 at normal temperature,
Shoulder portion 17 of second shaft portion 16 of shank portion 12 and connecting member 1
A gap c5 is formed between the other end face 18c and the other end face 18c.

The ball end mill 10 according to the present embodiment
Has the above-described configuration, and the method of fitting will be described next. In a state where the head portion 11 and the shank portion 12 are separated as shown in FIG.
In a state where the inner diameter d3 is increased to the outer diameters d1 and d2 or more by heating to about ° C, the head 11 is attached to the connecting member 18 from both ends thereof.
The first shaft portion 14 and the second shaft portion 16 of the shank portion 12 are inserted, and the tip surfaces 14b, 16b of both shaft portions 14, 16 are brought into contact with each other. Then, the connecting member 18 is cooled and contracted in the radial direction, so that the connecting member 18 and the two shaft portions 14 and 16 are shrink-fitted to each other by the interference so that the head portion 11 and the shank portion 12 are connected. At the same time, since the connecting member 18 also contracts in the longitudinal direction (the direction of the axis O3), a gap c4 is formed between the shoulder portion 15 of the first shaft portion 14 and one end surface 18b of the connecting member 18, and the second shaft A gap c5 is also formed between the shoulder 17 of the portion 16 and the other end face 18c of the connecting member 18. Further, if the connecting member 18 is cooled while being pressed and restrained in one direction of the shoulder 15 of the first shaft 14 and the shoulder 17 of the second shaft 16, a gap C4 or C5 is formed in only one of them. Will be. Thus, the ball end mill 10 shown in FIG. 1 is manufactured. In this state, the center axes O1, O2, and O3 are coaxial and coincide with the center axis O of the ball end mill 10.

When the ball end mill 10 is mounted on a machine tool (not shown) for cutting, a load is applied in the direction of the axis O due to the cutting resistance, but even in this case, the tip surface 14b of the first shaft portion 14 of the head portion 11 is also used. And shank part 12
Since the end surface 16b of the second shaft portion 16 is in contact with each other in the connecting member 18, the load is received by the machine tool via the head portion 11 and the shank portion 12, and the gaps c4 and c5 are reduced. Since there is no clogging and the overall length of the ball end mill 10 does not change, cutting can be performed with high precision. still,
When the head portion 11 is removed for replacement of the cutting blade, the interference fit is loosened by heating the connecting member 18,
The head 11 can be easily removed from the connecting member 18.

As described above, according to the present embodiment, the workpiece can be cut with high precision without changing the overall length of the ball end mill 10 in the cutting process.

Next, with respect to the ball end mill 10 according to the first embodiment, the tip end surface 14b of the first shaft portion 14 of the head portion 11 and the tip end surface 16 of the second shaft portion 16 of the shank portion 12 will be described.
A modified example of the contact mode b will be described. FIG. 4 shows the abutting state of the respective tip surfaces of both shaft portions.
Of the first shaft portion 14 has an elliptical plane inclined at an obtuse angle θ1 with respect to the axis O1. On the other hand, the tip surface 21 of the second shaft portion 16 of the shank portion 12
Is an acute angle θ2 (= 180 ° −θ) with respect to the axis O2.
It is an elliptical plane forming 1). Therefore, when the entire distal end surfaces 20 and 21 of both the shaft portions 14 and 16 are brought into contact with each other so that the axes O1 and O2 coincide with each other at the time of shrink fitting by the connecting member 18, the head portion with respect to the shank portion 12 can be obtained. 11 can be positioned. The two end surfaces 20, 21 of the two shaft portions 14, 16 each constitute an engaging portion.

Next, FIG. 5 shows a second modified example showing the abutting state of the respective end surfaces of both shaft portions. In FIG. 5, the tip end surface 23 of the first shaft portion 14 of the head portion 11 is formed by convex portions of two planes 23a and 23b whose cross section parallel to the axis O1 forms a V-shape. Passes. On the other hand, the distal end surface 24 of the second shaft portion 16 of the shank portion 12 has two flat surfaces 24a and 24 each having a V-shaped cross section parallel to the axis O2.
The axis O2 passes on the intersection ridge line of the two planes formed by the concave portion b. Therefore, if the convex distal end surface 23 and the concave distal end surface 24 are fitted as engagement portions by shrink fitting by the connecting member 18, the positioning of the cutting blade of the head portion 11 with respect to the shank portion 180 can be achieved. It can be performed in two directions at an interval of °.

Next, FIG. 6 shows a third modified example showing the abutting state of the tip surfaces of both shaft portions. In FIG. 6, the tip end surface 26 of the first shaft portion 14 of the head portion 11 has a concave portion 26a and a convex portion 2 having a substantially V-shaped cross section, for example, radially about the axis O1.
6b are formed alternately. On the other hand, on the distal end surface 27 of the second shaft portion 16 of the shank portion 12, for example, concave portions 27a and convex portions 27b having a substantially V-shaped cross section are alternately formed radially about the axis O2. When the concave portion 26a of the one distal end surface 26 and the convex portion 27b of the other distal end surface 27 and the convex portion 26b and the concave portion 27a are fitted to each other, the two distal end surfaces 26 and 27 are brought into contact with each other. Note that the distal end surface 26 of the first shaft portion 14 and the distal end surface 27 of the second shaft portion 16 each constitute an engaging portion. According to this configuration, the positioning of the cutting blade of the head portion 11 with respect to the shank portion 12 is determined by the concave portions 26a, 27a and the convex portions 27a, 27b of the both end surfaces 26, 27.
A large number can be set in the circumferential direction according to the number.

Next, a second embodiment of the present invention will be described with reference to FIGS. 7 and 8, and the same or similar parts and members as those in the first embodiment will be described using the same reference numerals. I do. FIG. 7 is a sectional view of a ball end mill according to the second embodiment, and FIG. 8 is an exploded sectional view of the ball end mill.
In the ball end mill 30 shown in FIG.
Reference numeral 1 is made of a cemented carbide, cermet, ceramic, or the like. The shank portion 31 is formed of a material having a higher coefficient of thermal expansion than the head portion 11, for example, steel. The head portion 11 has the same shape as that of the above-described first embodiment, and a first shaft portion 14 is formed at a base end portion 11b. On the other hand, the shank portion 31 has the tip 12a.
For example, a substantially cylindrical hole 32 having a smaller diameter than the outer peripheral surface 12c is formed, and a ring-shaped peripheral surface 33 is formed on the outer peripheral side. The hole 32 has a cylindrical inner peripheral surface 32a and a circular bottom surface 32b. The hole 32 is formed coaxially with the central axis O2 of the shank 31. Moreover, FIG.
As shown in the figure, the inner diameter d4 of the hole 32 is set to be smaller than the outer diameter d1 of the first shaft portion 14 of the head portion 11, and the dimensional difference (d1-d4) between the two is smaller than the interference during shrink fitting. Have been. The axial length (depth) S4 of the hole 32 is shorter than the length S1 of the first shaft 14 of the head 11 at normal temperature (S1
> S4) and S1 ≧ S4 even during heating.

With this configuration, if the first shaft portion 14 is inserted into the hole portion 32 and cooled while the shank portion 31 is heated at the time of shrink fitting, the shank portion 31 contracts in the radial direction. A gap c <b> 6 is formed between the shoulder portion 15 of the first shaft portion 14 and the peripheral surface 33 of the hole 32 in order to fit the first shaft portion 14 with an interference and shrink in the axial direction. Also in this case, since the distal end surface 14b of the first shaft portion 14 is in contact with the bottom surface 32b of the hole portion 32, the total length of the end mill 30 does not change due to the load during cutting.

Next, a third embodiment of the present invention will be described with reference to FIG. In the ball end mill 40 shown in FIG. 9, the shank portion 41 has the same configuration as that of the first embodiment, and is formed of cemented carbide, cermet, ceramic, or the like. Have. On the other hand, the head portion 42 is formed of a material having a higher coefficient of thermal expansion than the shank portion 21, for example, steel, and the base end portion 11b has a substantially cylindrical hole portion 43 having a smaller diameter than the outer peripheral surface 11c. A ring-shaped peripheral surface 44 is formed on the outer peripheral side. The hole 43 has a cylindrical inner peripheral surface 43a and a circular bottom surface 43b. The length S4 of the hole 43 is the second shaft 1 of the shank 41.
6, the inner diameter d4 of the hole 43 is set to be smaller than the outer diameter d2 of the second shaft portion 16, and the dimensional difference (d2-d4) between them is an interference in shrink fitting. It has been.

Also in this embodiment, by heating the head portion 42, the inner diameter of the hole portion 43 is enlarged, and the second shaft portion 16 of the shank portion 41 can be shrink-fitted. The tip end surface 16b of the second shaft portion 16 is in contact with the bottom surface 43b of the hole 43.

The material of one of the head portion and the shank portion is made of cemented carbide, cermet or ceramic, and the other material is made of steel or the like, but the material of each member is not limited to this. Can be adopted. Also, the materials need not necessarily have different thermal expansion coefficients, and may be the same. Even if the same material is used, the connecting member 18
Since the cylindrical thick portions of the holes 32 and 43 are larger than the outer diameter of the shaft portion, shrink fitting is possible. The present invention is not limited to the shrink fit, but may be a cold fit, and the shaft and the second shaft are cooled and contracted to form a tight fit with the connecting member 18 and the holes 32 and 43. May be. The first and second shaft portions 14, 1 shown in FIGS.
The configuration of each engaging portion 6 is the same as that of the shaft portion 1 in the other embodiment.
The present invention can also be applied to a configuration in which the tip surfaces 14b, 16b of the holes 4, 16 and the bottom surfaces 32b, 43b of the holes 32, 43 abut.

Alternatively, for example, a disk-shaped intermediate member may be inserted into the connecting member 18 or the holes 32, 43 to fit the shafts 14, 16 tightly. In this case, even if the lengths of the shafts 14 and 16 themselves are smaller than the lengths of the connecting member 18 and the hole,
The sum of the lengths of the mediating member and the shaft portions 14 and 16 may be larger than the length S3 of the connecting member 18 and the length S4 of the holes 32 and 43. Length will be included. The present invention also provides a shank part 12,
The present invention can be applied to the case where 31 and 41 are exchanged. In the above description, a rolling tool such as a ball end mill has been described as a cutting tool of the present invention, but the present invention is not limited to this and can be applied to a turning tool such as a boring bar.

[0024]

As described above, the interference-fitting cutting tool according to the present invention has a shaft portion on one of the head portion and the shank portion, and has a hole portion fitted on the shaft portion on the other side, and has the shaft portion and the shank portion. An interference is provided in one of the holes, the length of the shaft is greater than the depth of the hole, and the tip surface of the shaft is in contact with the bottom of the hole. There is no change in the overall length of the cutting tool when a load is applied in the direction, and cutting can be performed with high precision. In addition, since the engaging portions that engage with each other and prevent relative rotation are formed on the distal end surface of the shaft portion and the bottom surface of the hole, respectively, the head portion can be easily positioned with respect to the shank portion. At the same time, the fitting strength by the interference fit is improved.

In the interference-fitting cutting tool according to the present invention, the head portion and the shank portion each have a shaft portion, and both shaft portions are in contact with each other and fitted in the hollow portion of the connecting member. An interference is provided in any of the connecting members, and the sum of the lengths of both shaft portions is larger than the length of the hollow portion of the connecting member. Therefore, when a load is applied in the axial direction of the cutting tool during cutting processing. There is no change in the overall length of the cutting tool, and cutting can be performed with high precision. Further, since engaging portions for engaging with each other and preventing relative rotation are formed on the distal end surfaces of the both shaft portions, the positioning of the head portion with respect to the shank portion can be easily performed, and an interference fit is adopted. The fitting strength is improved.

[Brief description of the drawings]

FIG. 1 is a longitudinal sectional view of a main part of a ball end mill according to a first embodiment of the present invention.

FIG. 2 is an exploded sectional view of the ball end mill shown in FIG.

FIG. 3 is an enlarged view of a fitting portion of the ball end mill shown in FIG.

FIG. 4 is a diagram showing a first modification of the distal end surfaces of a first shaft portion and a second shaft portion in a contact state.

FIG. 5 is a diagram showing a second modification of the distal end surfaces of the first shaft portion and the second shaft portion in the contact state.

FIG. 6 is a view showing a third modification of the distal end surfaces of the first shaft portion and the second shaft portion in the contact state.

FIG. 7 is a sectional view of a ball end mill according to a second embodiment.

FIG. 8 is an exploded sectional view of the ball end mill shown in FIG.

FIG. 9 is a sectional view of a main part of a ball end mill according to a third embodiment.

FIG. 10 is a sectional view of a main part of a ball end mill according to the prior art.

[Explanation of symbols]

 10, 30, 40 Ball end mill 11 Head 12, 31, 41 Shank 14 Shaft 16 Second shaft 32, 43 Hole

Claims (4)

[Claims] 1. A cutting tool comprising a head part and a shank part connected to each other, wherein one of the head part and the shank part is provided with a shaft part, and the other part is provided with a hole part fitted with the shaft part. A tightening margin is provided in one of the shaft portion and the hole portion, wherein a length of the shaft portion is larger than a depth of the hole portion, and a tip end surface of the shaft portion is in contact with a bottom surface of the hole portion. And an interference-fitting cutting tool. 2. The tightening device according to claim 1, wherein engagement portions for engaging with each other and preventing relative rotation are formed on a front end surface of the shaft portion and a bottom surface of the hole portion. Fitting type cutting tool. 3. A cutting tool in which a head portion and a shank portion are connected, wherein a shaft portion is provided in each of the head portion and the shank portion, and the two shaft portions are brought into contact with each other and fitted into the hollow portion of the connecting member. And a tightening margin is provided in one of the two shafts and the connecting member, and the sum of the lengths of the two shafts is greater than the length of the hollow portion of the connecting member. Fitting type cutting tool. 4. The interference-fitting cutting tool according to claim 3, wherein engagement portions for engaging with each other and preventing relative rotation are formed on the end surfaces of the both shaft portions.