JPH0790410B2 - Cutting tool with small relief - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial application] The present invention relates to a cutting tool having a margin such as an end mill, a side cutter, a reamer, and a drill, and
The present invention relates to the improvement of a cutting tool such as a cutting tool having a double angle.

[Prior Art and Problems Thereof] In general, there are two types of cutting tools, one with an immediate second angle on the rear side of the cutting edge and one with a margin formed on the rear side of the cutting edge.

As an example of the former, for example, in a bite, the cutting edge is often broken immediately after the start of cutting. Further, for example, in a milling cutter, since an impact force is repeatedly stamped on the cutting edge, the cutting edge is likely to be chipped or chipped, which often shortens the tool life significantly.

Further, examples of the latter include a reamer and an end mill. FIG. 6 shows a cross section orthogonal to the cutting edge 1 in a conventional cutting tool having a margin. A margin 2 is formed in a portion of a predetermined width behind the cutting edge 1 in the rotational direction, and a margin 2 is formed on the rear side of the margin 2. A second take-up surface 3 having a predetermined clearance angle is formed in the portion.

Here, the margin 2 is formed on a cylindrical curved surface that is not secondarily cut, and it prevents chatter vibration of the cutting tool and makes a hole by making sliding contact with the inner wall surface of the machining hole without biting it. In machining, it has a function of improving the dimensional accuracy and surface roughness of the machined hole by the burnishing action. However, in actual cutting, the existence of the margin 2 may adversely affect various adverse effects.

For example, the work material may be welded to the rear portion of the margin 2, and this welding may progress to coagulate as the deposit 4. Such a deposit 4 is almost the same as the constituent cutting edge, and it is extremely hard and not only causes deep scratches on the inner wall surface of the work material,
In particular, when the cutting tool is a reamer, it may bite deeply into the work material and prevent the reamer from coming off the work material, or in some cases lead to a breakage accident. Moreover, as described above, the adhered matter 4 adhered to the margin 2 is extremely hard and not only requires a great deal of labor to be removed, but also deeply adheres to the fine irregularities on the polished surface of the margin 2. However, even if it is removed with an oil grindstone or the like, it often re-adheres when the cutting process is performed, which causes serious problems such as defective products and unusable cutting tools.

Further, since the heat generated by the friction between the margin 2 and the inner wall surface of the work material is remarkable, the cutting speed cannot be increased.
Even at a normal cutting speed, the heat generated in the margin may not be suppressed depending on the cutting oil.

Here, the margin 2 has such an adverse effect as described above for the following reason.

That is, since most of the work material is an elastic material, the drilled hole contracts immediately after that and tightens the cutting tool.
In this case, the compressive force that the margin 2 receives from the work material is removed by the cutting action of the cutting edge 1 in the vicinity of the cutting edge 1 which is the ridge line portion of the margin 2, but increases as it goes backward in the rotational direction. Moreover, since it is difficult for the cutting oil to cool the work material or prevent the welding from reaching the margin 2, heat is easily generated and the affinity with the work material is increased. It causes an adhesion phenomenon.

Furthermore, when carrying out cutting processing by traversing the work material,
Since the margin 2 moves while drawing a trochoidal curve, the above-mentioned inconvenience is more prominent than in the case where a tool is fed in the axial direction for machining. For example, when machining with a cutting allowance of 0.2 mm / rev, the clearance angle of the margin 2 with respect to the work material becomes minus 33 ″, and the rear part of the margin 2 is the cutting edge 1 of the ridge part.
It is about 0.0067mm ahead of. Therefore, the compressive force due to the lateral feed is added to the compressive force due to the contraction of the work material, and a great compressive force acts on the margin 2.

[Object of the Invention] The present invention has been made in view of the above circumstances, and in a cutting tool having a dihedral angle such as a milling cutter, it is possible to effectively prevent chipping of a cutting edge, and A cutting tool having a margin is intended to provide a cutting tool capable of solving various troubles by preventing welding and adhesion of a work material on the margin.

[Means for Solving the Problems] The cutting tool of the present invention forms a first second cutting surface having a predetermined clearance angle on the rear side of a margin or a cutting edge, and A second cutting face having a clearance angle larger than that of the first cutting face is formed on the rear side, and the margin width is 0.05 mm or less, and the first cutting face in a cross-sectional view orthogonal to the margin or the cutting edge. The clearance angle of the numbered surface is 1 ° to 2 °, and the clearance width obtained by adding the width of the first second numbered surface to the margin width is 0.05 mm to 0.5 mm.

[Embodiment] FIGS. 1 to 5 show an embodiment of the present invention, and FIG. 2 is a perspective view showing an end mill. In the figure, reference numeral 10 is a tool body. The tool body 10 has a columnar shape that is rotated about the axis, and has three tip pockets 11 extending from the axis toward the outer peripheral side at the tip thereof.
Are formed at equal intervals in the circumferential direction, and cutting edges 12 are formed on the tip ridges of the wall surfaces of the chip pockets 11 that face the direction of rotation. In addition, there are three twist grooves 13 on the outer circumference of the tool body 10.
Is formed, and the tip end portion of each twist groove 13 is continuous with the chip pocket 11.

Here, as shown in FIG. 1, the wall portion of the spiral groove 13 which faces the rotation direction is a rake face 14. A cutting edge 15 is formed on the outer peripheral ridge of the rake face 14, and a margin 16, a first second cutting surface 17 and a second second cutting surface 18 are formed in a portion of a predetermined width behind the cutting edge 15. The small relief 19 made of is formed.

The margin 16 has a cylindrical curved surface that is not doubled, and its margin width T is set to 0.05 mm or less.
However, the margin width T may be zero (that is, there is no margin). Further, the first second take-up surface 17 is formed flat in a portion of a predetermined width behind the margin 16 and has a clearance angle α. Further, a clearance angle β larger than the clearance angle α is provided behind the first cutting surface 17.
A second flat cutting surface 18 marked with is formed.

Here, the clearance angle α of the first cutting surface 17 is set to 1 ° to 2 °. Further, in the direction of the margin width T, the clearance width W obtained by adding the width of the first second cutting surface 17 to the margin width T is set to 0.05 mm to 0.5 mm. Further, the clearance angle β of the second cutting surface 18 is set to 8 ° to 20 °.
The line segment 1 that serves as a reference for the clearance angles α and β in FIG. 1 is the tangent line on the most rear end side of the margin 16.

Here, the grounds for limiting the above numerical values will be described with reference to specific experimental results.

The reason why the margin width T is set to 0.05 mm or less: If the margin width T exceeds 0.05 mm, the work material is likely to be welded because the friction with the work material becomes severe.

The reason why the clearance angle α of the first cutting surface 17 is 1 ° to 2 °: Table 1 shows the results when various clearance angles α are selected and drilling is performed.

As can be seen from Table 1, when the clearance angle α is 30 ', the cutting edge 15 is the same as when drilling with a conventional end mill.
Does not perform a cutting action, and streaks are formed on the inner wall surface of the hole due to friction with the first second cutting surface 17. However, the clearance angle α is 1.0 °
In this case, the cutting edge 15 performs a cutting action, and as a result, no streak is formed on the inner wall surface of the hole. That is, the clearance angle α is 1 °
By the above, the compressive force received from the inner wall surface of the hole by the cutting action of the cutting edge 15 can be removed.

However, when the workpiece is laterally fed for cutting, as described above, the outer circumference of the end mill moves along a trochoidal curve, and thus the clearance angle α needs to be set to a larger value. Generally in the cutting process that is currently performed,
The cutting allowance may be increased to 1.0 mm / rev, but in this case, assuming that the clearance angle α is zero, the first cutting surface
Clearance angle for workpiece 17 is minus 35 '. Therefore, in order to prevent the second contact of the first chamfered surface 17, it is necessary to set the clearance angle α with a margin, but increasing the clearance angle α unnecessarily means that It causes a new problem such as chipping and chatter vibration of the tool due to the decrease of the vibration. Therefore, the clearance angle α is
It is necessary to set the minimum value that can prevent the friction between the first second cutting surface 17 and the inner wall surface of the hole. From the results of Table 1, 2 ° is set as the upper limit.

The clearance width W, which is obtained by adding the width of the first flank 17 to the margin width T, is set to 0.05 mm to 0.5 mm: When the clearance width W is less than 0.05 mm, the cutting edge strength decreases and the cutting edge 15
This is because chipping of is likely to occur. Particularly, in the lateral feed cutting, the cutting edge 15 cuts intermittently, and therefore the cutting edge 15 is easily damaged by the impact force at that time. On the other hand, the clearance width W is
If it exceeds 0.5 mm, the wear width becomes wider with respect to the wear depth, as will be described later, and the life is shortened.

Further, the clearance angle β of the second cutting surface 18 is set to 8 ° to 20 °. When the clearance angle β is less than 8 °, the wear width with respect to the wear depth becomes wide as in the above case. From
This is because if the clearance angle β exceeds 20 °, the rigidity of the cutting edge becomes insufficient when a large cutting resistance acts such as heavy cutting of steel or the like.

In the end mill having the above structure, since the small relief 19 is formed behind the cutting edge 15, the friction between the outer peripheral portion of the tool and the inner wall surface of the hole can be reduced. Therefore, it is possible to prevent welding of the work material to the margin 16 and the first cutting surface 17, and to effectively prevent serious troubles such as generation of streaks on the inner wall surface of the hole due to the adhered matter. it can. Further, since the amount of generated heat is small, it is possible to cope with high-speed cutting, and it is possible to enhance the cooling effect of the cutting oil even at a normal cutting speed.

By the way, as described above, a cutting tool having a double angle immediately behind the cutting edge (that is, a cutting tool having no margin), such as a conventional milling cutter, is repeatedly stamped by intermittent cutting. There is a drawback that the cutting edge is easily damaged by the impact force. However, even for such cutting tools, the small relief as described above
By forming 19, the wedge angle of the cutting edge is increased and the edge strength is increased. Therefore, it is possible to prevent chipping or chipping of the cutting edge without impairing the function as a milling cutter. As a result, the rake angle of the cutting edge and the clearance angle β of the second cutting surface 18 can be set to be larger than the rake angle and the second angle of the conventional tool. The hitting can be effectively prevented, and the synergistic effect with the increase of the cutting edge strength can significantly improve the cutting performance. further,
Even if the cutting edge portion is made of a material having a high hardness such as CBN, it is possible to perform the cutting process without any trouble.

Further, in the above end mill, the clearance width W obtained by adding the width of the first second cutting surface 17 to the margin width T is set to 0.5 mm or less. Therefore, as shown in FIG. 1 and FIG. Even when the portion shown by the alternate long and short dash line in the figure is worn as in the conventional end mill, the wear width L is narrower than that of the conventional end mill. Therefore, the tool life can be significantly extended.

FIG. 4 shows the relationship between the cutting distance and the width of the outer peripheral wear when the small-relief end mill of the present invention (where the clearance angle α is 1 ° 30 ′) and the conventional end mill are used for cutting. In the figure, a cemented carbide end mill with a small relief of the present invention, is a conventional cemented carbide end mill, is a conventional end mill made of cemented carbide and having a titanium coating on the surface, both with the same margin as the conventional margin have. Also, the cutting conditions are tool outer diameter: 16m
m, work material: FC25, other feed etc. are the same.

As can be seen from FIG. 4, in the end mill with small relief, the outer peripheral wear is remarkably reduced. It was also confirmed that the end mill of the present invention has a life of 3 times or 4 times. In addition, since the compression force acting on the margin is large, almost the entire outer peripheral portion of the end mill is burnt black due to heat generation, whereas in the end mill with a small relief, only the vicinity of the cutting edge is burnt.

Further, FIG. 5 shows the relationship between the cutting distance and the width of the outer peripheral wear when cutting is performed with the work material as S50C. The outer diameter of each tool was 20 mm and the cutting conditions were the same. In the figure, a cemented carbide end mill with a small relief of the present invention, a cemented carbide end mill having the same margin as the conventional one on the outer peripheral portion, and a cemented carbide end mill with a second angle immediately behind the outer peripheral cutting edge.

From FIG. 5, it can be seen that the end mill with a small relief is significantly less peripherally worn than an end mill having a conventional margin even if the work material is S50C having high tensile strength. In addition, the end mill with small relief has a wider wear width than the conventional end mill with a double angle when the cutting distance is short, but the wear width is much narrower as compared with the conventional end mill as the cutting distance becomes longer. The effect of Small Relief 19 is remarkable.

Moreover, in the end mill with small relief, the initial wear is relatively stable, which means that the tool life is extended.

Further, the present invention was applied to a reamer, and holes having a clearance angle α of 1 ° and 1 ° 30 'were drilled.

In a reamer with a clearance angle α of 1 °, some friction was generated between the first secondary cutting surface 17 and the inner wall surface of the hole, but due to the use of cutting oil, problems such as adhesion of cutting chips to the outer circumference of the tool It didn't happen at all. Further, in the reamer having a clearance angle α of 1 ° 30 ', there was no friction with the inner wall surface of the hole, but a slight chatter vibration occurred. However, the chatter vibration had no effect on the dimensional accuracy and surface roughness of the hole, and a machined surface that was smoother than the conventional reamer was obtained.

In addition, in the above-mentioned embodiment, the first cutting surface 17 is formed flat, but it may be formed in a convex curved surface or a concave curved surface as shown in FIG. Further, the present invention is not limited to end mills, reamers and drills, but in addition, the same effect can be obtained even if small reliefs are formed on various cutting tools such as a bite, a throwaway tip, a side cutter, and a milling cutter. Is.

[Effects of the Invention] As described above, in the cutting tool with the small relief of the present invention, the first cutting edge having a predetermined clearance angle is formed on the rear side of the margin or the cutting edge, and the first cutting edge is formed. A second cutting surface having a clearance angle larger than that of the first cutting surface is formed on the rear side of the counting surface, and the margin width is 0.05 mm or less, and a cross-sectional view orthogonal to the margin or the cutting edge. The clearance angle of the 1st secondary cutting surface is 1 ° to 2
°, the clearance width obtained by adding the width of the first cutting edge to the margin width was set to 0.05 mm to 0.5 mm, so that a secondary angle was immediately added to the rear of the cutting edge like a milling cutter. With a cutting tool, it is possible to prevent the occurrence of chipping of the cutting edge. As a result, the clearance angle of the second cutting surface can be set larger than that in the conventional case, so that the second hitting can be effectively prevented. In addition, the cutting edge is CB
Even if it is made of a material having a high hardness such as N, it is possible to perform the cutting process without any trouble.

Further, in the case of a cutting tool having a margin such as a reamer, it is possible to reduce friction between the tool outer periphery and the work material, so that heat generation of the tool outer periphery is reduced and at the same time Welding can be prevented in advance. As a result, troubles such as scratches on the work material can be prevented, and various excellent effects can be obtained such that the tool life can be significantly extended.

[Brief description of drawings]

1 to 5 are views showing an embodiment of the present invention, and FIG. 1 is a second view showing details of a cross section orthogonal to a margin.
Fig. 2 is a sectional view taken along line I-I, Fig. 2 is a perspective view showing an end mill, Fig. 3 is a sectional view taken along line III-III in Fig. 2 showing a modification of the cutting tool shown in Fig. 1, Fig. 4 and FIG. 5 is a diagram showing the relationship between the cutting distance and the outer peripheral wear width, and FIG. 6 is a sectional view orthogonal to the margin of the conventional cutting tool. 1 ... Cutting edge, 2 ... Margin, 3 ... Secondary surface, 10 ...
… Tool body, 13 …… Twisted groove, 15 …… Cutting edge, 16 …… Margin, 17 …… First chamfered surface, 18 …… Second chamfered surface.

Claims (2)

[Claims] 1. A first cutting edge having a predetermined clearance angle is formed on the rear side of a margin or a cutting edge, and a clearance angle of the first cutting edge is formed on the rear side of the first cutting edge. Forming a second relief surface having a larger clearance angle than
The margin width is 0.05 mm or less, and the clearance angle of the first cutting edge is 1 ° in a cross-sectional view orthogonal to the margin or the cutting edge.
A cutting tool with a small relief, characterized in that the clearance width obtained by adding the width of the first cutting surface to the margin width of 2 ° is 0.05 mm to 0.5 mm. 2. The clearance angle of the second cutting surface is 8 ° to 20 °.
The cutting tool with a small relief according to claim 1, wherein