JPS5837087B2 - Cutting tools - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a cutting tool, and particularly to a ball end mill suitable for creating a recess including a curved surface portion.

A ball end mill is usually used to cut a spherical recess.

This is a blade with a curved part formed on a shaft with a ball-shaped tip, and by rotating it around the axis of the shaft, it cuts a spherical recess. There is.

Such a ball end mill is useful for machining curved surfaces of molds and the like by attaching it to the main shaft of a milling machine, for example, and rotating it around its axis and moving it in three dimensions.

The blade of a conventional ball end mill has a curved shape when viewed from the side of the shaft, but when viewed from the bottom of the tip of the shaft, the blade extends in a straight line in the radial direction from the center of the shaft. .

With such a shape, when cutting by rotating the shaft, the cutting edge of the blade comes into contact with the workpiece almost simultaneously from the center to the outer periphery, resulting in large cutting resistance and large impact force. As a result, the cutting edge is easily damaged, making heavy cutting impossible.

To solve this problem, three-dimensional cutting can be achieved by making the cutting edge of the blade convex in the direction of rotation of the shaft, or by making the rake face of the blade slope with respect to the axis of the shaft. There are known devices that have been devised to do this.

However, in all of these methods, the shape of the blade is complicated, making it difficult to manufacture the blade, and it is also difficult to re-grind the blade when it wears out, making it difficult to cut highly accurate spherical concavities. It had the disadvantage of being ugly.

Since the cutting edge of the blade part is not simple, it is difficult to use a throw-away type.

SUMMARY OF THE INVENTION An object of the present invention is to eliminate such conventional problems and provide a rotary cutting tool that has a high spherical surface machining accuracy, has a simple cutting edge shape, and is easy to manufacture.

Another object of the present invention is to provide a cutting tool that allows chips to be easily discharged from the blade portion, has low cutting resistance, and has a low impact force during cutting so that the cutting edge is not easily damaged.

Another object of the present invention is to provide a cost-effective throw-away type cutting tool by detachably attaching the blade to the shaft.

Another object of the present invention is to provide a cutting tool that does not interfere with a workpiece without cutting off the rear part of the blade in the rotational direction, although the cutting tool is manufactured with a circular cutting blade in the shape of a rotating body. It is to be.

Another object of the present invention is to provide a throw-away type cutting tool that can rotate the blade part by 180 degrees and use the rear part in the rotational direction as a new cutting edge when the front part in the rotational direction of the cutting edge is worn out.

The cutting tool described below has a blade at the end of the shaft,
The face shape of the blade portion is formed by a part of the side surface of a rotating body having a substantially truncated conical shape, and the cutting edge of the blade portion is formed by a twilling portion between the side surface and the bottom of the rotary body shape. It is something.

In this case, there are two modes: one in which the axis of the blade section is offset from the axis of the shaft section, and one in which the axis of the blade section intersects with the axis of the shaft section.

In the former case, as shown in FIG. 2 or 3, the axis 4 of the shaft and the axis 9 of the blade are completely misaligned, and as shown in FIG. 4 and the axis 9 of the blade do not intersect, but in the bottom view of the tool, the center of the blade may be on the X-axis. In this way, the axis of the blade may deviate from the axis of the shaft. By rotating the tool around the axis of the shank, a curved surface of rotation is created whose radius of rotation is the distance from the axis of the shank to each point on the cutting edge.

In the latter case, the shape of the traverse between the side surface of the rotating body shape and the bottom part, that is, the shape of the cutting edge, is the outline of a circle defined by the side surface of the rotating body shape and a plane perpendicular to the axis of the blade part. By forming the shank, the distances from the point where the axis of the shank intersects with the axis of the blade are all equal to each point on the cutting edge, and by rotating the shank around that axis, the distances between both axes are equal. A spherical surface centered at the intersection is created.

In the latter case, the rear part of the blade in the rotational direction tends to rub against the workpiece, which may damage the cutting edge or deteriorate the roughness of the machined surface.

In order to avoid such a phenomenon, in the cutting tool according to the present invention, the axis of rotation of the rotating body forming the blade part passes through a point at a predetermined distance from the axis of the shaft part at an angle. By shaping the blade in this manner, the rotation radius at the rear of the blade in the rotation direction is made smaller than the rotation radius at the front of the blade in the rotation direction, and as a result, the rear part of the blade in the rotation direction and the workpiece are rubbed. It is configured so that there is no such thing.

Further, the flank surface of the blade portion is formed by the bottom surface of the rotating body shape,
The rotating body-shaped blade portion and the shaft portion are each made separately, and the blade portion is configured as a throw-away type that can be removed from the shaft portion.

Hereinafter, the present invention will be explained based on examples with reference to the drawings.

FIG. 1 is a front view of a cutting tool showing an embodiment of the present invention.

Also, Fig. 2 is a bottom view of Fig. 1, and Fig. 3 is a view of arrow F in Fig. 1.
FIG.

A cutting tool 1 according to the present invention includes a shaft portion 2 and a blade portion 3 attached to an end thereof.

The shaft portion 2 has one end connected to the main shaft (not shown) of the machine tool directly or via a colled chuck (not shown), and rotates around the axis 4 and in the axial direction and perpendicular direction to the axis. and can be given.

As shown in the figure, the tip of the shaft portion 2 is formed into a spherical shape, and a blade portion attachment surface 5 is formed in a portion thereof.

The blade portion 3 has a generally disk-like shape as a whole, and is removably attached to the blade attachment surface 5 of the shaft portion with, for example, a bolt 6.

The blade portion 3 may be fixed to the blade attachment surface 5 of the shaft portion by brazing or the like.

The rake face 7 of the blade part 3 is formed by a part of the side surface of a rotating body shape having an apex, for example, a part of the cone-shaped side surface, and the cutting edge 8 of the blade part 3 is formed by a part of the side surface of the rotating body shape and the rotating body shape. It is formed by the bottom and the ridge of the body shape.

A flank 10 of the blade portion is formed at the bottom of the rotating body shape following the cutting edge 8.

The bottom portion is formed so as not to come into contact with the workpiece during actual cutting.

In the blade portion 3 having such a configuration, its axis 9 is arranged at an arbitrary angle γ with respect to the axis 4 of the shaft portion in the front view of FIG.

However, the present invention is not limited to the case where the axis 4 of the shaft part 2 and the axis 9 of the blade part 3 intersect, and as shown in FIG. 2 or 3, the axis 9 of the blade part 3 is The blade part 3 can be attached to the shaft part 2 at a certain distance e from the axis 4 of the blade part 2.

In this case, as shown in the bottom view of FIG.
The center of is separated from the X-axis by a distance e in the rotational direction of the shaft portion 2.

Further, in this embodiment, an arbitrary point on the cutting edge of the blade portion 3, for example, point A, is separated from the axis 4 of the shaft portion 2 by a distance a.

This aspect is clearly shown in FIGS. 1 and 2.

A cutting tool 1 of the present invention shown in FIGS. 1 to 3 is attached to a main shaft (not shown) of a machine tool and rotated around an axis 4 of a shaft portion 2 in the direction of arrow C.

A point E on the cutting edge draws a circle 11 whose radius is the distance D between that point and the center O of the shaft portion (FIG. 2).

The radius D of this circle 11 appears as a radius U on the workpiece 12 in FIG.

Therefore, the entire cutting edge forms a curved surface 41 on the workpiece 12.
will be created.

Chips (not shown in FIG. 1) are removed from the rake face 7 of the blade part 3.
The blade rolls upward along the blade portion 3 and is easily discharged from the upper portion 14 of the blade portion 3 to the outside of the workpiece 12.

After all, the workpiece 12 is subjected to three-dimensional cutting by such a cutting tool 1, so that cutting resistance is small and high cutting efficiency is obtained.

Furthermore, when the shaft portion 2 rotates around its axis 4, the radius of the rotation locus at the rear of the cutting edge 80 in the rotational direction is smaller than the radius of the rotational locus at the front of the cutting edge 8 in the rotational direction. There is no rubbing against objects, and the machined surface roughness is improved.

Further, since the rear part of the cutting edge 80 in the rotational direction and the workpiece do not rub against each other, the cutting edge is less likely to be damaged.

Furthermore, when the front part of the cutting edge in the 80 rotation direction wears out, the rear part in the rotation direction can be used as a new cutting edge, so by rotating the blade part 1800 revolutions and reattaching it to the shaft, the blade part can be used over the entire circumferential area without waste. be able to.

In this case, if the cutting tool is rotated about its axis and fed, the workpiece 12 can be machined with a hollow spherical bearing surface 41 as shown in FIG. A.

In the cutting tool 1 shown in FIG. 5, the rake face 7 of the blade part 3 rotates around an axis (indicated by an imaginary line 9) that passes obliquely in the vicinity of the axis (indicated by an imaginary line 4) of the shaft part 2. The cutting edge 8 is formed by a part of the side surface of a rotating body, and the part A of the cutting edge 8 is located in the vicinity of the axis 4 ahead of the tip of the shaft 2.

Strictly speaking, the axis 9 intersects the axis 4 of the shaft 2, and the point A of the cutting edge 8 is placed on the axis of the shaft 2, thereby making it possible to machine a spherical bottomed recess.

The angle of inclination γ between the axis 9 and the axis 4 of the shaft portion 2 is approximately 5°.
-700.

When the shaft 2 is rotated around its axis 4, each point on the cutting edge 8 (for example, point 150 in FIG. Draw a circle (for example, circle 16 in Fig. 6) with a radius of the distance indicated by the symbol B of
Since it is equidistant from 0, a spherical surface is ultimately created by the entire cutting edge 8.

Therefore, the other end of the shaft portion 2 is connected to the main shaft (not shown) of a machine tool by a known method, and the tip of the shaft portion 2 is connected to the workpiece 12.
When the spindle is rotated in the direction of arrow C and fed in the axial direction while being brought into contact with a pre-roughly machined recess, a spherical surface 13 is formed in the recess of the workpiece 12.

In this case, the chips 17 roll obliquely on the rake face 7 and are discharged from the outer portion 18 of the rake face 7 to the outside of the recess of the workpiece, thereby reducing the cutting resistance.

After all, three-dimensional cutting is performed on the workpiece 12 by such a blade portion, and the depth of cut is large, resulting in high cutting efficiency.

In such a blade part, the cutting edge that can actually participate in cutting is the cutting edge in the upper part from the line 19 that coincides with the X axis in FIG. .

Therefore, in the present invention, the portion 210 is referred to as an ineffective cutting edge.

However, the ineffective cutting edge 210 portion comes into contact with the concave surface of the spherical surface 13 due to rotation of the blade.

As a result, no depth of cut can be applied and effective cutting cannot be performed.

In order to prevent this, as shown in FIGS. 13 and 14, the rake face and the relief surface, which constitute the ineffective cutting edge, are removed as indicated by the reference numeral 22.

Alternatively, as shown in FIG. 15, the blade portion 3 is formed into an arc shape with a central angle δ of 180° or more, and the ineffective cutting edge portion is cut out in a straight line as shown by the reference numeral 23, and A portion of the bottom of the blade is removed as shown at 24.

As a result, even if the depth of cut of the tool is increased, there will be no interference between the ineffective cutting edge and the workpiece, and an effective depth of cut can be given to the cutting edge 8, making heavy cutting possible.

Further, the flank surface 10 is formed in the shape of an arbitrary rotary body having the axis 9, following the bottom surface of the rotary body shape forming the rake face.

Therefore, in the cutting tool of the present invention, the effective cutting edge is a part of a circle, and both the rake face and flank face have a simple shape that utilizes the side surfaces of the rotating body, so it is different from conventional ball end mills with complicated cutting edge shapes. In comparison, its production is extremely easy.

The bottom of the blade forming the flank 10 is formed to exist within a sphere whose center is the intersection 20 of the axis 4 of the shaft 2 and the axis 9 of the blade 3 and whose radius is the distance from the intersection to the cutting edge. This also reduces interference between the bottom and the workpiece.

When the blade portion becomes worn due to use, the bolt 6 is removed and the blade portion 3 is replaced with a new blade portion.

With the conventional complicated cutting edge shape, accurate re-grinding is impossible when it wears out, making it difficult to machine perfectly spherical concave parts, but with the present invention, the cutting edge is circular, making it possible to improve the accuracy. Since it is easy to create a spherical envelope surface by rotating the cutting edge, it is possible to process a spherical surface with high accuracy.

In addition, because of three-dimensional cutting, machinability is good and chip evacuation is also good.

By forming the rake face shape of the blade portion 3 by a part of the side surface of a right circular cone, as shown in FIG. 7, the cutting tool of the present invention has a simpler shape and is easier to manufacture. Machinability also improves.

In this case, in order to increase the rigidity of the cutting edge, the apex angle β of the right circular cone should be made small, and in order to improve the cutting edge, the apex angle β should be made small.
It is better to make it as large as possible.

Experiments have shown that the apex angle β of a right circular cone under various cutting conditions
It was confirmed that the angle can be within the range of 10° to 160°.

As shown in Fig. 8, by forming one generatrix of the right circular cone along the axis 4 of the shaft part 2, it is possible to exchange blades of similar shapes with different outer diameters of the cutting edges and to create spherical surfaces with different radii. Cutting is possible.

Note that making the generatrix of the right circular cone line along the axis 4 of the shaft portion 2 means making the generatrix coincide with the axis 4 of the shaft portion 2; It also includes a mode in which the generatrix line is parallel to the axis line with a slight deviation.

9 and 10 show a cutting tool having an auxiliary cutting edge 26 in addition to the above-mentioned blade portion.

The blade portion of the cutting tool of the present invention is a portion 2 near the outside of the shaft portion 2.
5 (Fig. 5), the cutting properties of the cutting edge are not good.

In particular, when the inclination angle γ between the axis 4 of the shaft 2 and the axis 9 of the blade is 45° or more, the portion near the outside of the shaft 2
The workpiece No. 5 has a tendency to leave uncut parts due to the rotation of the blade.

In such a case, by providing an auxiliary cutting edge 26 on the circumferential side of the shaft portion 2 as shown in FIG. 9, the uncut portion left by the blade portion 3 can be removed.

By installing the auxiliary cutting blade 26 at an angle with respect to the axis 4 of the shaft portion 2, the overall cutting efficiency can be increased.
In addition, it is effective in discharging chips that have moved upward in the figure while rolling on the rake surface 7 of the blade portion 3 to the outside of the workpiece.

Furthermore, by appropriately setting the shape and mounting position of the auxiliary cutting blade 26, it is possible to simultaneously machine a cylindrical surface by the auxiliary cutting blade 26 in addition to a spherical surface by the blade portion 3 on the workpiece 12.

Further, by providing an auxiliary cutting edge on the opposite side of the blade portion 3 to the shaft portion 2, the balance due to rotation of the tool can be improved and vibrations and shocks can be reduced.

The auxiliary cutting edge 26 may be fixed to the shaft portion by brazing, or may be of a removable throw-away type.

Furthermore, as shown in FIG. 10, by shaping a portion of the auxiliary cutting blade 26 into a circular blade, it is possible to cut not only cylindrical surfaces but also spherical surfaces as in the conventional ball end mill.

In addition to the above, the auxiliary cutting blade may have a circular cutting edge and be attached to the shaft so that its central axis intersects with the axis of the shaft or passes near the axis of the shaft. .

Of course, a plurality of such auxiliary cutting edges may be attached to the shaft portion.

In addition, in the illustrated embodiments, except for the example shown in FIG. An appropriate inclination angle is set within the range of the angle according to the desired shape of the workpiece.

Next, the cutting tool of the present invention shown in FIGS. 11 and 12 will be explained.

As mentioned above, the back side of the effective cutting edge that can be used for actual cutting, that is, the part of the ineffective cutting edge 21 (Fig. 6) among the ridge lines of the rake face and flank face that make up the cutting edge, is This results in rubbing the spherical surface.

In order to solve this problem, the cutting tool shown in FIGS. 11 and 12 is one in which the blade portion 3 is attached to the shaft portion 2 so as to be shifted in a predetermined direction.

The cutting edge 8 of the effective cutting edge shown in FIG. 5 corresponds to the thick imaginary line 30 in FIGS. 11 and 12.

In addition, the thin virtual line 310 is indicated by the reference numeral 21 in FIG.
corresponds to the ineffective cutting edge of

The reference numeral 320 represents one point A on the cutting edge in FIG.

Now, the blade part 3 is moved from the position shown by the imaginary line in Figs. 11 and 12, with the diameter 33 of the blade part (appearing on the X-axis in Fig. 11) passing through the point A on the cutting edge, that is, point 320, as the axis. It is rotated by a predetermined angle α to the position shown by the solid line.

A point 27 on the cutting edge 30 at the front in the rotational direction of the shaft shown by the imaginary line is directed toward the tip of the shaft 2 as indicated by the reference numeral 27a.
That is, it moves in a direction away from the shaft portion 2.

Therefore, the breather 28 on the cutting edge, which becomes an ineffective cutting edge, moves in the direction closer to the shaft portion 2, as indicated by the reference numeral 28a.

When the shaft portion 2 is rotated in the direction of the arrow in FIG. 11 in this state, the depth of cut at the cutting edge 27a increases, but a gap is created between the cutting edge 28a and the created spherical surface.

As a result, even when the blade portion 3 rotates, the ineffective cutting edge portion does not come into contact with the spherical surface.

Therefore, the blade part is shown in FIGS. 13, 14, or 1.
It is possible to make an effective incision even if it is formed into a complete disk shape, instead of forming it into a shape with a part cut out as shown in FIG.

As a result, even if the cutting edge of the effective cutting edge becomes worn due to use, the unworn, non-effective cutting edge can be used by rotating the blade 3 1800 revolutions and attaching it to the shaft 2 again. As a result, the entire circumferential area of the circular cutting edge of the blade portion 3 can be used without waste.

Moreover, since it is not a rotating body shape with a part removed, but a complete rotating body shape, manufacturing is easy.

[Brief explanation of the drawing]

Figure 1 is a front view of the cutting tool when the cutting edge is not on the axis of the shaft, Figure 2 is a bottom view of Figure 1, Figure 3 is a side view as seen from the direction of arrow F in Figure 1, Figure 4 is a cross-sectional view of a workpiece in which a spherical bearing surface is machined using the cutting tool shown in Figure 1, Figure 5 is a front view of a cutting tool in which the rake face is formed by a rotating body-shaped side surface, and Figure 6 is a cross-sectional view of a workpiece in which a spherical seat surface is machined using the cutting tool shown in Figure 1. Fig. 7 is a front view of a cutting tool whose beveled surface is formed by the side surface of a right cone, and Fig. 8 is a cutting tool in which one of the generatrix lines of the right cone coincides with the axis of the shaft. Figures 9 and 10 are respectively front views of cutting tools with auxiliary cutting edges, Figure 11 is a bottom view of the cutting tool with the blade shifted and attached to the shaft, and Figure 12 is a view of the cutting tool with the blade attached to the shaft. Figure 13 is a bottom view of the cutting tool with the ineffective cutting edge removed, and Figure 14 is the ineffective cutting edge removed. FIG. 15 is a bottom view of a cutting tool having an arc-shaped cutting edge. 1... Cutting tool, 2... Shaft, 3...
...Blade part, 7...Rake face, 8...
・Blade edge, 10... Flank surface, 12... Workpiece, 14... Spherical bearing surface, 26...
Auxiliary cutting blade.

Claims (1)

[Scope of Claims] 1. In a cutting tool in which a blade is removably provided at the tip of a shaft, the rake face 7 of the blade is set at a point separated by a predetermined distance e from the axis 4 of the shaft. It is formed by a side surface of a substantially truncated conical shape lacking the apex of a substantially conical shape having a rotation axis 9 that passes through at an angle γ inclination, and the flank surface 10 of the blade portion is a bottom surface of the substantially truncated conical shape. The cutting edge 8 of the blade portion is formed by the ridge line between the side surface and the bottom surface of the truncated conical shape, and the blade portion is attached to the mounting surface 5 provided at the tip of the shaft portion with a fastening member 6. The rotational axis 9 of the blade section passes through the axis line 4 of the shaft section and the cutting edge A of the cutting edge 8 is on the axis line 4 of the shaft section. The leading edge A of the cutting edge 8 is moved in parallel by a predetermined distance a in the direction of the outer circumference of the shaft within a plane parallel to both the axis 4 of the shaft and the axis of rotation 90 of the blade, and further in the direction of the outer circumference. When the shaft is rotated around its axis 4, the cutting edge has an 80-rotation trajectory. A cutting tool characterized in that it is configured to create a concave curved surface on a workpiece. 2. In a cutting tool in which a blade is removably provided at the tip of a shaft, the rake face of the blade has a rotational axis 9 that obliquely passes through a point separated by a predetermined distance from the axis 4 of the shaft. The blade part is formed with a side surface of a substantially truncated conical shape lacking the top of the conical shape, the flank of the blade part is shaped by the bottom face of the substantially truncated conical shape, and the cutting edge of the blade part is formed by the bottom surface of the substantially truncated conical shape. It is formed by the ridge lines of the side and bottom surfaces of a substantially conical shape, and the blade part is removably attached to a mounting surface provided at the tip of the shaft part by a fastening member, and the rotation axis 9 of the blade part is Passing through the axis 4 of the shaft part and with a position where the leading edge 32 of the cutting edge is on the axis 4 of the shaft part as a reference, from that position, the cutting edge 30 at the front in the cutting tool rotation direction passes through the cutting edge 32 of the cutting edge. The cutting tool is mounted so that it is rotated by a predetermined angle α in the direction away from the shaft with the diameter 33 of the circular cutting edge as the axis, and when the shaft is rotated around its axis 4, the front part of the cutting tool in the direction of rotation is A cutting tool characterized in that a 300-rotation locus of a cutting edge is configured to create a concave curved surface on a workpiece.