JPH0453615A - End mill - Google Patents

Abstract

PURPOSE:To secure such an end mill that is suitable for finish-cutting for profile forming against high hardness materials in addition to ease of manufacture by forming an axial perpendicular sectional form of a cutting edge part into a polygon of more than a triangle, and making up a twisted cutting edge with a ridgeline made by each apex in the axial direction. CONSTITUTION:A cutting edge twisted by a ridge 12 made in the axial direction by each apex of a polygon of more than triangle in an axial perpendicular section, for example, a regular hexagon, is formed on the outer circumferential surface of a tool body 11, while the axial perpendicular section of the regular hexagon is formed into a taper form, where its diameter is reduced in proportion as going to the tip end, and a tool material should be a cemented carbide and a sintered hard alloy treated with TiN coating. Since the axial perpendicular sectional form is polygonal, the number of cutting edges is increased, and edge strength and tool rigidity loath are excellent, so that wear of the cutting edge and chipping are reduced, while such a helix angle as the same in the tool rotational direction is given to the edge, thereby absorbing an impact at time of cutting, and even in case of a high hardness work material, cutting is made achievable at a feed rate several times over the conventional end mill, thus an excellent profile form and a finished surface can be secured.

Description

Detailed Description of the Invention [Field of Industrial Application] This invention relates to an end mill for finish cutting that forms a slope or curved surface on the contour of a high-hardness material, which has a plurality of cutting edges with twists on the outer periphery. It is.

[Conventional technology]

An end mill shown in FIG. 2 is an example of this type of cutting tool for cutting general materials such as steel using a conventional machine tool such as a milling machine. These are generally arranged on a virtual cylinder. It has a sharp cutting edge with a helix angle and a positive rake angle, followed by a large flute 14, making it easy to cut into the workpiece, and has good chip evacuation, making it extremely easy to work with. It is something. here,
The rectangular cutting edge can be used in an optimal shape by appropriately setting the angle according to the properties of the workpiece material. For example, for materials with high hardness and poor machinability, a sharp cutting edge will not only cause severe wear but also easily cause chipping during cutting. The cutting edge specifications were improved by increasing the cutting edge, making the cutting groove shallower, increasing tool rigidity, reducing wear and tear on the cutting edge, and preventing chipping.

In end mills, it is known that the greater the number of teeth, the longer the tool life, especially when cutting high-hardness materials. Therefore, increasing the number of blades was one of the improvement measures. Furthermore, when the hardness of the workpiece material increases and the sharpness deteriorates, methods have been used to improve the number of teeth and cutting edge specifications while simultaneously lowering the depth of cut and other cutting conditions.

When cutting high-hardness materials, tool materials are required to have sufficient hardness and strength for the workpiece material. High speed steel and cemented carbide are commonly used as tool materials for end mills, but cemented carbide coated with a hard substance such as TiN is often used for high-hardness materials. However, even in this case, when applied to a conventional rectangular end mill, the work material hardness H
There was a limit to what RC55 could cut.

[Problem that the invention seeks to solve]

Expectations for cutting high-hardness materials are increasing in a wide variety of fields. However, when it comes to high-hardness materials that reach HRC60, such as hardened tool steel, even if we try to improve cutting edge specifications such as rake angle, relief angle, or number of teeth, end mills with conventional shapes are not suitable for practical use. value, and it is no longer possible to respond by changing the cutting conditions.

For this reason, grinding or electric discharge machining is often used, but these have slow machining speeds and problems with machining efficiency.

Regarding tool materials used in cutting, there are ceramics, CBN, diamond, etc. for ultra-hard materials, but although these have extremely high hardness, they are relatively brittle, and are not suitable for end milling, which requires interrupted cutting. In addition to being prone to chipping during cutting, the processability is poor and the tool shape cannot be obtained freely, so there is a problem that it can only be used for limited applications such as micro-cutting.

[Object of the present invention]

The present invention aims to eliminate the above-mentioned drawbacks and provide an end mill that is easy to manufacture and suitable for contour forming and finishing cutting of high hardness materials such as hardened materials.

[Means to solve the problem]

In order to achieve the above object, the present invention forms a cutting edge in which the cross-sectional shape perpendicular to the axis of the cutting edge part is a polygon of triangle □ or more, and the edges formed by each vertex in the axial direction are twisted, The cutting edge is shaped so that it can be transferred to the workpiece.

In addition, technical measures have been taken to use a super hard alloy coated with a hard substance such as TiN as the tool material to enable cutting of highly hard materials due to the synergistic effect with the square shape described above.

[For production]

There are U.S. Pat. It is something that

For example, referring to Fig. 1, the case where the bottom blade is rotated clockwise as is self-evident is illustrated here, but the cross-sectional shape perpendicular to the axis is hexagonal and has a rightward twist angle. are doing. In the case of a hexagonal cross section, the number of peripheral cutting edges corresponds to 6 teeth, and as shown in the cross-sectional view in Fig. 5, the rake angle θr and clearance angle θC in the direction perpendicular to the axis are -60'' and 30°, respectively. , therefore, the blade angle θt is 120''. In other words, it is possible to obtain cutting edge strength and tool rigidity suitable for cutting high hardness materials up to HRC 60. Furthermore, compared to conventional end mills, it has the effect of allowing a relatively large number of teeth even when the diameter is small. The chip pocket, which is essential for end mills, does not have many cutting scenes when it comes to finish cutting, so only the part surrounded by the solid circumscribing the ridge that forms the cutting edge and the faces formed by each side of the polygon is sufficient. I know that. Here, the cutting edge has a helix angle in the right direction, so even if the cutting edge is large, the impact at the time of cutting is alleviated.
It has good biting and shows sufficient machinability for hard materials.

As for the tool material, a coated carbide alloy was used, and the synergistic effect with the square shape made it possible to cut high-hardness materials. Due to its rectangular shape with a large negative rake angle, it has the effect of preventing peeling, which is the most undesirable phenomenon for coatings that occurs during cutting.

[Example] FIG. 1 shows an example of the present invention. Although the case where the tool body 11 is used with clockwise rotation is shown here, the outer periphery of the tool body 11 has
Edge 12 formed in the axial direction by each vertex of a regular hexagonal cross section perpendicular to the axis
forms a cutting edge with a right helix angle of 30°. Furthermore, the axis-perpendicular cross-section of the regular hexagon has a tapered shape in which the diameter decreases toward the tip. Here, the taper angle is 3°. The tool dimensions are 8 mm in diameter, 20 mm in blade length, and 60 mm in total length.The tool material is cemented carbide and TiN coated cemented carbide. This product of the present invention was compared with solid end mills made of cemented carbide and coated cemented carbide shown in FIG. 2 having the same dimensions, by cutting alloy steel for cold work molds tempered to a hardness of HRC62. Here, the depth of cut is 0.1 in the radial direction.
+m and dry cutting was performed. The results are shown in FIGS. 6 and 7, and it is clear that the end mill of the present invention is more than three times as durable as the conventional end mill and clearly superior in finished surface roughness. In other words, with the conventional cemented carbide solid end mill, chipping of the cutting edge became severe after only 0.3 m of cutting, and cutting had to be stopped after 1 m. The product of the present invention did not cause chipping even at a feed rate three times that of conventional end mills (it was still usable after cutting a length of 6 m).Also, even with the roughness of the cutting surface, solid carbide end mills did not cause chipping. The product of the present invention has a Rw of 5μraRmax compared to about 18μmRmax due to the
It was good around ax. That is, this square shape is shown to be well compatible with the coating.

Furthermore, when a highly finished surface is required, it is preferable to use cermet, ceramics, etc. depending on the hardness of the workpiece material.

Here, the number of angles of the polygon and the helix angle of the peripheral cutting edge can be appropriately designed in consideration of the hardness of the workpiece, the material of the tool, and the diameter of the tool.

An example of a tool similar to the present invention is a polygonal cross-section end mill for machining tapered grooves. This is used as a means to increase tool rigidity in end mills with a small diameter and long blade length, and is different in that it is used only for deep groove cutting.

〔Effect of the invention〕

As described above, according to the present invention, since the cross-sectional shape perpendicular to the axis is polygonal, the number of cutting edges is increased, and the cutting edge strength and tool rigidity are excellent, thereby reducing wear and chipping of the cutting edges. Furthermore, by providing a helix angle that is the same as the tool rotation direction, the impact during cutting is alleviated, and as a result, it is not only possible to cut high-hardness workpieces at several times the feed rate of conventional end mills. It is now possible to obtain excellent contour shapes and finished surfaces.

[Brief explanation of the drawing]

Figures 1A and 1B show an embodiment of the present invention, with Figure A being a front view and Figure B being a side view. Figure 2A. B shows an example of a conventional end mill, FIG. A is a front view thereof, and FIG. B is a side view thereof. FIGS. 3 and 4A and 4B show other embodiments of the present invention, with FIG. A being a front view and FIG. 4 being a side view. FIG. 5 is an explanatory diagram of the rake angle and clearance angle of the peripheral cutting edge when the cross-sectional shape perpendicular to the axis is a regular hexagon according to the present invention;
FIGS. 6 and 7 are explanatory diagrams showing comparison results between the end mill of the present invention and a conventional end mill.

Claims (3)

[Claims] (1) A plurality of twisted cutting edges are formed on the outer periphery of the tool body, the cross-sectional shape perpendicular to the axis of the cutting edge portion is a polygon of trigon or more, and the ridge formed by each vertex in the axial direction forms the cutting edge. 1. An end mill for forming a material, the cutting edge of which is inscribed in a virtual solid having an outline of a shape to be transferred to a workpiece to be cut. (2) The end mill according to claim 1, which has a tapered cutting edge whose diameter changes linearly in the axial direction. (3) Claims 1 to 2, characterized in that the tool material is a coated cemented carbide.
End mill described in section.