JP2003159610A - Radius end mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide an excellent multiedged, large helical angle end mill which has improved cutting ability, and is suitable for heavy cutting such as grooving, and has a long tool life, and is applicable to finish cutting by smoothing discharge of chips and by preventing vibration in cutting, though multi-edged, large helical angle end mills tend to cause chip packing. <P>SOLUTION: The radius end mill is characterized in that, in the radius end mill having helical cutting edges 2 on the outside periphery thereof and circular cutting edges at the outside periphery side of end cutting edges 8, the shape of the gash in the cross section perpendicular to the helical cutting edges is formed by the curves including the rake face, the bottom, the back flank, and the tertiary relief flank of the neighboring cutting edge, and approximately forms a U shape, and the rake face of the helical cutting edges is a curved face elongating in the radial direction from the rotational axis of the end mill in the range from the inside more than 5% of the outside diameter of the end mill to the cutting edge, and the rake face of the circular cutting edges is formed as a continuous convex surface along the cutting edge from the end of the cutting edge to the end of the end cutting edge. <P>COPYRIGHT: (C)2003,JPO

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an end mill mainly used for machine tools for cutting steel or metal materials.

[0002]

2. Description of the Related Art An end mill used for rough machining must have a chip space capable of smoothly discharging a large amount of chips generated by a cutting action and a tool strength capable of withstanding a cutting force which increases in proportion to the cutting depth. Therefore, a two-flute end mill having a small number of blades is generally used. For finishing, the maintenance of sharpness is more problematic than with regard to chip control, so that a 4-flute end mill or a multi-blade end mill is used. On the other hand, end mills are generally elongated and weak in tool strength, and their application to roughing tends to be a problem, but there are many ways to improve them. As an example, Japanese Patent Laid-Open No. 7-178612.

[0003]

Generally, the blade shape of an end mill is composed of each element of land width including a rake face, a blade bottom, a back face, and a flank face, of which the back face is intended to reinforce the land width. It is made to have a convex arc-shaped bulge. This narrows the blade groove, reduces the roundness of the blade bottom, forcibly bends the chips, and causes unnecessary cutting resistance. In particular, when grooving as an example of rough machining, both side surfaces made by themselves become walls, and chip evacuation further depends on the blade shape. When a large amount of chips are generated, such as grooving, and there are restrictions on chip discharge,
The conventional shape of the flute has a problem that chip clogging occurs and tool life is short. Similarities occur with viscous work materials such as stainless steel. This is because the chip curl radius of stainless steel is larger than that of carbon steel. As described above, this is one of the reasons why the two-blade end mill with a small number of blades is used for rough machining, but it goes without saying that it is desirable to use both rough and finish in common.

On the other hand, the conventional product has an end mill having three or more twisted cutting edges with a shallow groove and a rake face with a rake face, and the cutting edge adjacent to the blade bottom in a cross-sectional view perpendicular to the axis. By connecting up to the third surface in a substantially straight line, there is no obstruction in the chip discharge direction, the chip is smoothly discharged with a small rake angle, and it is also compatible with groove cutting. However, sticking to a straight line from the blade bottom to the third face of the adjacent cutting edge makes the blade bottom shallower, which has been recognized as a hindrance to the curl of chips.

[0005]

SUMMARY OF THE INVENTION The present invention has been made to solve the above problems, and in a multi-blade heavy-twist end mill where chip removal tends to be a problem, chip discharge is smoothed and cutting vibrations and the like are prevented. In addition, the present invention provides an excellent end mill which has improved machinability, is suitable for heavy cutting such as groove cutting, has a long tool life, and can be applied to finish cutting.

[0006]

In order to solve the above problems, the present invention provides a radius end mill having a twisted cutting edge on the outer periphery and an arcuate blade on the outer peripheral side of the bottom blade, which is perpendicular to the cutting edge. The shape of the groove groove surface in the direction cross section is such that the shape curve from the rake face to the blade bottom and the back surface to the third face of the adjacent cutting edge is substantially U-shaped, and the rake surface of the cutting edge is from the cutting edge. Within 5% or more of the blade diameter, a curved surface that faces the radial direction from the center of rotation, and the rake surface of the circular arc blade is a convex surface that is continuous along the cutting edge from the cutting edge to the bottom edge. A radius end mill having a characteristic, more specifically, the cutting edge is 3 or more and the helix angle is 30 degrees to 5 degrees.
0 degree, the core thickness of the end mill is 60% to 75% of the blade diameter, and the water squeeze angle of the bottom blade of the end mill is 0.5 degree to 15 degrees,
The rake angle of the cutting edge is approximately 0 degree, the rake angle of the bottom edge is 0 degree in the axial direction or a regular angle of 0 degree or more, and the land width of the cutting edge is 10 degrees of the blade diameter in a cross section in a direction perpendicular to the blade. % To 20%
Is a value of.

[0007]

In view of the shape of the groove surface of the cross section perpendicular to the outer peripheral cutting edge, chips are cut out in the direction perpendicular to the edge and flow out. Therefore, it is desirable to increase the helix angle for the purpose of improving machinability. Further, if the helix angle is increased, the interval between the cutting edges becomes narrow, which hinders chip disposal. By removing the convex arc-shaped bulge, the blade groove can be widened, and a large roundness of the blade bottom can be provided to guide the chips, thereby facilitating the chip disposal. A 30 degree twist is typically used in general purpose end mills. Although a strong twist is adopted for the purpose of improving the machinability, according to the present invention, a blade groove equivalent to a 30-degree twist can be secured even with a strong twist. The size of the flute is also limited by the number of flutes and the core thickness. If the number of blades is large even if the twist is loose, the interval between the cutting edges in the chip outflow direction becomes narrow. Therefore, the present invention is significant even if the twist is 30 degrees.

The rake angle is related to sharpness and cutting edge strength. Since the rake angle is set to about 0 degree, the cutting edge strength is guaranteed even if there is no convex portion on the back surface. Furthermore, since the tangent line of the blade groove is concave so that the tangent line at any position passes within the cross-sectional shape, the rake face directly below the cutting edge becomes a hook shape and the blade angle near the cutting edge is increased to enhance the reinforcing effect. Obtainable. Since the blade groove is a concave curved surface and is a curved surface having a small curvature according to the regulation of the core thickness, chips are promptly removed along the rake face without staying in the blade groove. Therefore, it does not promote cutting vibration. Since the cutting heat generated is also removed together with the chips, thermal damage is mitigated. The rake angle is about 0 degree, but it may be in the range of about −5 degrees to +5 degrees.

The rake face of the radius blade portion is composed of an outer peripheral rake face and a bottom blade rake face, and a mountain-shaped projection is formed at a portion where they intersect. The stronger the twist, the harder the protrusions become, and the larger the cutting resistance locally, the more likely damage is. The rake face of the radius blade part is used as an independent convex rake face to disperse the local resistance evenly and reduce damage. The rake angle of the radius blade part does not increase to a regular angle, and the strength at biting can be maintained.
The watermelon angle of the bottom blade is set so that the bottom blade and the cutting surface do not come into contact with each other in a wide range, and is normally 0.5 to 3 degrees. The arc blade has a cutting edge contact length equal to the arc length as compared with the square blade. Since the length is long, make the watermark angle large and keep it balanced. Especially in inclined cutting, it has an effect of reducing contact and helping to remove chips.

Since the rake angle of the bottom blade is 0 degree or a regular angle and is provided independently of the rake surface of the outer peripheral cutting edge, the machinability of the bottom blade can be secured without being affected by the helix angle and the core thickness. Since a part of the bottom blade forms a flat blade at the tip of the outer peripheral cutting edge, the sharp edge part of the cutting edge, which is the weak point of the strong twisting edge, is strengthened and the cutting edge wear is distributed over the length of the flat edge. And avoid local wear. Although the length of the flat blade changes depending on the conditions, it may be set to a value of about 0.2 to 0.5 mm so as not to be affected by the crater wear generated in this portion.

By the above operation, the chip discharging property in the groove cutting is improved, and the deep groove cutting becomes possible even with three or more blades. Especially, it is easy to cut stainless steel that is not easily deformed by chips and has a long tool life. It can also be applied to difficult-to-cut materials such as heat resistant steel. Further, since the chips do not hinder the cutting action, the cutting vibration is small. As a result, the surface roughness is good, and highly accurate finishing with less run-down is possible, and it can be neatly cut even when cutting long standing walls. Further, since the tip of the outer peripheral cutting edge is reinforced, it is suitable for grooving and pocket processing where chips are likely to accumulate, and the tool life is extended even in corner processing and contour processing where the cutting edge tip is heavily used. That is, it can be used for both rough cutting and finish cutting. With the corner R blade, chips can be easily removed in three-dimensional cutting, and heavy cutting is possible.

The land width of the outer peripheral cutting edge (flank surface, second surface, etc.) is 10% to 20% of the blade diameter. Since there is no convex back surface, make it larger than usual to balance the blade and groove. The land width of a general end mill is about 10% of the blade diameter in a cross section perpendicular to the axis. If there is a convex back surface, the land width is made uniform so that a heel step is required, but since there is only a concave curved surface, the land width is made even without the heel step.

By applying the present invention, a back surface having a convex arc-shaped bulge extending from the rake surface to the third surface of the adjacent cutting edge through the blade bottom is eliminated, and therefore twisting is performed for the purpose of improving machinability. It is possible to take a large angle, which narrows the interval between cutting edges in a cross section perpendicular to the blade,
Since the chips are cut out in the direction perpendicular to the blade and flow out, even if this interval is narrowed, the convex groove is removed to widen the blade groove, and a large rounded bottom to guide the chips. Can be provided to facilitate the chip disposal. The U-shaped roundness of the present invention is limited by the number of blades and the core thickness. The larger the number of blades, the smaller the radius of roundness. As described above, when the helix angle is large and the cutting edge spacing in the chip outflow direction is narrow, or when the core thickness is large and the number of blades is large, it is difficult to secure a sufficient groove in a general end mill. However, the effect of the present invention is remarkable.

Next, the tip of the outer peripheral cutting edge is connected to the bottom blade with an arcuate blade, and the rake face of the arcuate blade is a convex surface which is continuous along the cutting edge from the outer peripheral edge to the bottom edge, By setting the rake angle of the blade to 0.5 to 15 degrees, the rake face of the radius blade portion is composed of the rake face of the outer peripheral blade and the rake face of the bottom blade, so that the intersection of both rake faces Appears like a mountain. As in the present invention, in the case of the end mill having a large helix angle, the mountain-shaped protrusions are large, and therefore the cutting edge is likely to be damaged by receiving a local cutting force. In order to prevent this, the convex surface is continuous. The bottom blade has a large water-repellent angle of 0.5 to 15 degrees so that the bottom blade can be smoothly chipped. With the above operation, first, the chip discharging property in the groove cutting is improved, and even the cutting edge having three or more blades can perform deep groove cutting. In particular, stainless steel, which is hard to deform chips, can be easily cut and has a long tool life. It can also be applied to difficult-to-cut materials such as heat resistant steel. Further, since the chips do not hinder the cutting action, the cutting vibration is small. As a result, the surface roughness is good, and highly accurate finishing with less run-down is possible.
With regard to the cutting shape, pocket machining where chips are easily accumulated is facilitated and the tool life is extended.

Next, since the rake face has a rake angle of approximately 0 degrees at the cutting edge, and is a concave curved surface that faces the radial direction away from the center of rotation at least within 5% of the blade diameter from the cutting edge, the rake angle is It is possible to prevent the strength of the cutting edge from deteriorating due to the conformal angle, and to increase the cutting edge angle in the vicinity of the cutting edge by the curved rake face to obtain a reinforcing effect. Further, since the rake angle does not become a large negative angle, the machinability is not deteriorated, and the generated chips are promptly removed along the rake face without staying in the blade groove. Therefore, it does not promote cutting vibration. Since the cutting heat generated is also removed together with the chips, the thermal damage of the cutting edge caused by the temperature rise is mitigated. The rake angle is about 0 degrees, but -5
If the angle is small, the rake face becomes a curved surface that faces the radial direction in a portion less than 5% of the blade diameter when the angle is small.

Further, since the rake angle of the bottom blade of the end mill is set to 0 ° or a regular angle of 0 ° or more in the axial direction and is provided independently of the rake face of the outer peripheral cutting edge, the helix angle and the core thickness It is possible to secure the machinability of the bottom blade without being affected, and on the other hand, a part of the bottom blade forms a flat blade with a minute length at the tip of the outer peripheral cutting edge, which results in a strong twist. It is possible to reinforce the sharp edge part of the cutting edge, which is the weak point of the blade, and disperse the wear of the cutting edge to change the blessing. Here, the length of the flat blade varies depending on the diameter of the end mill and the usage conditions, but is 0.2 to 0.2 so that it is not affected by the crater wear that occurs in this portion.
A numerical value of about 0.5 mm should be taken.

Further, according to the present invention, the land width of the outer peripheral cutting edge is set to a value of 10% to 20% of the blade diameter in a sectional view in the direction perpendicular to the blade. First, the land width is the width of the land 5 in FIG. A flank from the cutting edge, a second surface continuous with the flank, and a second surface are formed to maintain the clearance between the work piece and the work piece. In the present invention, since there is no back surface having a convex arc-shaped bulge, the blade and the groove are balanced by setting the value larger than that of a general end mill.
A general end mill including conventional products has a land width of about 10% of the blade diameter in a cross section perpendicular to the axis.

With the above operation, first, the chip discharge property is improved in groove cutting, and even with three or more cutting edges, deep groove cutting is possible. In particular, stainless steel, which is less likely to deform chips, becomes easier to cut, and the tool life is long.
It can also be applied to difficult-to-cut materials such as heat resistant steel. Further, since the chips do not hinder the cutting action, the cutting vibration is small.
As a result, the surface roughness is good, and highly accurate finishing with less run-down is possible. Also, because the tip of the outer peripheral cutting edge is reinforced,
Not only groove cutting and boquetting where chips easily accumulate,
The tool life is extended even in corner machining and contour machining where the tip of the cutting edge is heavily used. That is, an end mill that can be used for both rough cutting and finish cutting is obtained. Further, the present invention is
The land width of the outer peripheral cutting edge is set to a value of 10% to 20% of the blade diameter in a cross-sectional view in the direction perpendicular to the blade. First, the land width is the width of the land 6 in FIG. This is composed of a flank and a second surface, a third surface, etc. which are continuous with the flank, and maintains the clearance between the work piece and the work piece. In the present invention, since there is no back surface having a convex arc-shaped bulge, the blade and the groove are balanced by setting the value larger than that of a general end mill. A general end mill including conventional products has a land width of about 10% of the blade diameter in a cross section perpendicular to the axis. Hereinafter, a detailed description will be given based on examples.

[0019]

(Embodiment 1) In both of the present invention 1 and conventional example 2, the end mill body 1 has a helix angle 3 of the outer peripheral cutting edge 2 of 43 degrees,
Ultra fine particle cemented carbide was used as the material of the four blades and end mill, and TiAlN coating was applied after grinding. In the present invention example 1, in the shape of the cross section perpendicular to the cutting edge of the line AA shown in FIG. 1, as shown in FIG. 2, from the rake face 4, the blade bottom 5, the back surface 6 to the third surface 7 of the adjacent cutting edge. Smoothly ground into a U-shape. In Conventional Example 2, similarly, in the shape of the cross section perpendicular to the cutting edge shown in FIG. 3, there is a convex ridge on the back surface. Comparative cutting was performed using the above two samples. The cutting depth was 8 mm in both width and depth, and the feed rate was used as a variable for cutting. The work piece is cold die steel SKD11 (hardness HB
200) and the cutting conditions were a rotation speed of 3200 rpm, a cutting speed of 80 m / min, and a length of 250 mm was sequentially increased for each cutting to observe the cutting condition.

As a result, Example 1 of the present invention has a feed rate of 60.
0, 800, 1000, 1200, 1400 mm / mi
n, and it withstood cutting, and a chip occurred at the tip of the bottom blade at 1600 mm / min. Since the cutting loads up to the feed rate of 600 mm / min did not differ significantly between the two, it was judged that the above performance difference was due to the difference in chip removing ability, that is, the U-shaped smooth blade shape was successful. . In the conventional example 2, when the feeding speed is 600 mm / min, the cutting edge is clogged with chips and the blade part becomes red-heated, and the feeding speed is 80
It was broken at 0 mm / min.

Next, the present invention was applied to side surface cutting, which is slightly convenient for removing chips. The incision was a side cut with a width of 2 mm and a depth of 15 mm to cut structural carbon steel S50C (hardness HB180). The cutting conditions are rotation speed 3100 rpm, cutting speed 10
0 m / min, feed rate 580 mm / min constant,
The cutting lengths were compared. In Example 1 of the present invention, chipping occurred on the outer peripheral edge after cutting 10 m, but no damage was observed on the bottom edge. Needless to say, in the end mill cutting, the cutting is started from the tip of the end mill bottom blade, and the load from each direction concentrates on one point and acts on this portion. In a conventional end mill including Conventional Example 2, this portion is particularly likely to be sharp, which causes local damage. In Conventional Example 2, with a cutting length of 1 m, a large chip was generated at the tip of the bottom blade, and the cutting could no longer be continued. In this way, the effect of the flat blade provided on the rake face of the strong helix blade on the reinforcement of the tip of the cutting edge is clear, and the synergistic effect with the U-shaped groove is exerted, and the influence on the tool life is further great. There is something.

(Embodiment 2) Next, a description will be given based on each component of the end mill. As Example 3 of the present invention, FIG. 4 shows an end mill having a blade diameter of 8 mm and a blade width of 8 mm, in which the rake angle of the tip portion is approximately 0 degrees, the land width 9 is 1 mm, and the groove depth is approximately 1.3 mm. That is, the land width 9 is 12% of the blade diameter ratio, and the core thickness is 68%. As shown in FIG. 2, the cross section of the blade at right angles is U-shaped from the rake face 4, the blade bottom 5, the back face 6 to the third face 7 of the adjacent cutting edge. Since the rake face 4 is formed of a curved surface, it does not face the rotation center side, and a large blade angle is obtained. As shown in FIG. 5, a part of the bottom edge of the outer peripheral cutting edge forms a flat portion 11 having a minute length. Since the axial rake angle of the bottom blade 8 is 5 degrees, the flat blade and the outer peripheral blade are bent and come into contact with each other. Also,
The material used was ultrafine particle cemented carbide and was TiAlN coated. As Comparative Example 4, as shown in FIG. 3, the back surface has an arcuate bulge with a blade diameter of 8 mm, a helix angle of 30 degrees,
With a rake angle of 10 degrees, the groove depth is 1.8 mm, and the land width is 1 mm
Carbide 4-flute end mill of was used. The same TiAlN coating as in Inventive Example 3 was applied.

In the cutting test, the width and depth of the cutting depth are 8
mm groove cutting was performed with the feed rate being a variable. The work piece is cold die steel SKD61 (hardness HB20
The cutting condition was 0), the rotation speed was 3200 rpm, the cutting speed was 80 m / min, and the cutting condition was observed by sequentially increasing the feed speed for each cutting of 250 mm in length. Inventive Example 3 is
Feed rate 600, 800, 1000, 1200, 140
It has a low vibration of 0 mm / min and withstands cutting well, 160
At 0 mm / min, chipping occurred at the tip of the bottom blade. The amount of chips discharged at a feed rate of 1400 mm / min is about 9
0 cc / min, which is more than 10 times the value commercially recommended for coating end mills of the same size. Since the cutting loads up to a feed rate of 600 mm / min did not differ greatly between the two, it was judged that the above performance difference was due to suitability for chip removal, that is, a U-shaped smooth edge shape without an undercut portion. It has been successful. This is because the tip of the cutting edge has been strengthened to withstand high feed, and the strengthening of the tip has obtained a remarkable effect. Conventional example 4 is
When the feed speed is 600 mm / min, the cutting edge becomes clogged with chips and the blade part becomes red heat, and the feed speed is 800 mm / mi.
It was broken when it was n.

Example 3 As Example 5 of the present invention, in order to confirm the action of the flat blade, the same blade shape as that of Example 1 of the present invention was used, and the blade diameter was 1
A 0 mm end mill was used. Blade groove depth of about 1.6 mm,
The land width is 1.2 mm. The material used was ultrafine particle cemented carbide and was TiAlN coated. Conventional example 2 was also tested. The cutting test is a side cut with a width of cut of 2 mm and a depth of 15 mm, which is structural carbon steel S50C (hardness HB
180) was cut. Cutting conditions are rotation speed 3100 rp
m, cutting speed 100 m / min, feed speed 580 mm /
The cutting length was compared until the cutting edge was damaged while the min was kept constant.

In Example 5 of the present invention, chipping occurred on the outer peripheral cutting edge after cutting 10 m, but no noticeable damage was observed at the tip portion of the cutting edge provided with the flat blade. Needless to say, in the end mill cutting, the cutting is started from the tip portion of the outer peripheral cutting edge, and the load from each direction concentrates on one point and acts on this portion. In the end mill having a strong twist like the example 5 of the present invention as well as the example 2 of the prior art, this part is particularly apt to be sharp, so the strength of the cutting edge is reduced, which causes local damage. However, since the flat blade is provided in the present invention, the load at the time of biting can be supported by the entire flat length 12, and the effect of reinforcing the tip of the cutting edge to prevent chipping and dispersing wear is remarkable. By reducing the damage on this part, U can be eliminated smoothly and cutting edge wear can be suppressed.
The effect of the V-shaped groove works effectively, and the synergistic effect of both is obtained to obtain a longer tool life. In Conventional Example 2, when the cutting length was 1 m, a large chip was generated at the tip of the outer peripheral cutting edge, and the cutting had to be stopped.

Example 4 Using Example 1 of the present invention, a test was conducted by engraving a cavity as shown in FIG.
The workpiece is S50C material (hardness HRC13), and the diameter is 2
A cavity with a depth of 00 mm and a depth of 20 mm is engraved. Rotation speed 2100 rpm, cutting speed 66 m / mi
n, feed rate 750 mm / min, depth of cut is 20
The inner wall was spirally cut to a width of 1 mm and a width of 1 mm. Although a cavity with a diameter of 200 mm is finally obtained, at the start of cutting, it starts from a small drill hole, so cutting is done within a small diameter circle with a large curvature, chip removal is difficult, and the cutting fluid is jetted and discharged. Although it assists, the workability is still extremely poor. Further, the cutting edge not only has a cutting action, but also hardened chips may be caught and cut again, which may accelerate damage. In Example 1 of the present invention, chips were bitten in this work, but they were reliably removed, and the cutting edge was not chipped, and stable work could be performed. The surface roughness of the processed surface was better than that of the comparative product. In the cavity processing, the final machined surface after cutting for a long time remains as the machined surface, so this evaluation is extremely valuable. Compared with the conventional example in which sudden damage such as chipping is unavoidable, the example of the present invention is characterized by stable results and high reliability.

The cutting action in the twisted blade end mill is such that chips are discharged in the direction perpendicular to the cutting edge, so that the blade shape analysis in the cross section perpendicular to the cutting edge is required. The larger the helix angle, the larger the deviation from the cross section perpendicular to the axis. The present invention is intended to obtain a blade groove of the same size as seen in a cross section perpendicular to the axis in a strong-twist blade in which the blade groove spacing becomes narrow. Similar deviations occur not only in the shape of the flutes but also in the rake angle and the clearance angle, but the rake angle of the outer peripheral cutting edge is set to approximately 0 degrees, so that the right angle direction and the right angle direction may not matter. When the flat blade is provided, if the rake angle is a regular angle, the rake face of the bottom blade becomes narrower, but by setting the rake angle to approximately 0 degrees, the rake face of the bottom blade becomes wide and a sufficient reinforcing effect is obtained.

(Embodiment 5) As a sixth embodiment of the present invention, FIGS.
The test was carried out with an end mill having a helix angle of 43 degrees, a rake angle of 0 degrees, a blade diameter of 10 mm with a blade groove depth of about 1.6 mm, and a circular blade 13 at the corner of four blades. As shown in FIG. 2, the sectional shape of the cutting edge of Example 6 of the present invention is such that the rake face 4, the blade bottom 5, the back face 6 to the third face 7 of the adjacent cutting edge are smoothly provided in a U shape. As shown in FIG. 8, the tip of the outer peripheral cutting edge is connected to the bottom blade by a circular arc blade 13 having a radius of 2 mm, and the rake face 14 of the circular arc blade 13 is such that the outer peripheral rake face and the bottom blade rake face are smoothly continuous. It was ground to a convex surface.
The water mark angle 15 of the bottom blade is 7 degrees. The material used was ultrafine cemented carbide and was TiAlN coated.
For comparison, as Comparative Example 7, a carbide 4-flute end mill having a rake angle of 10 degrees, a groove depth of 2 mm, and a blade diameter of 10 mm was used. The same TiAlN coating as in Inventive Example 6 was applied. As shown in FIG. 3, there is a convex arc-shaped bulge on the back surface. An arc blade having a radius of 2 mm was provided at the tip of the outer peripheral cutting edge, but the rake surface was not ground to a convex surface. The cutting test
The cutting width and depth are both 10 mm, and the tool protrusion amount is 40 mm, and the feed rate is a variable.
C and SUS304 were used. For the work material S50C, the cutting speed was 50 m / min, and dry cutting was performed. For the work material SUS304, the cutting speed was 20 m / min, and the oil-based cutting oil was used.

As a result, when the feed rate was gradually increased from the lowest value as a variable, in the case of S50C, the feed rate was 500, 750, 1250 mm / m in Example 6 of the present invention.
Even after cutting to in, there was little vibration and the cutting could be continued. No abnormal damage such as chipping was observed at the tip. It was broken at a feed rate of 1500. In Comparative Example 7, mechanical vibration was severe at the time when the feed rate was increased to 750 mm / min, and the breakage occurred. Conventional products had large scratches on the back surface, leading to chipping and breaking.
Therefore, the suitability of chip removal is the difference between these limits. It was confirmed that the product of the present invention can be discharged without depositing chips in the blade groove even if the feeding speed is increased.

Similarly, in SUS304 cutting, the feed rate was gradually increased from the lowest value using the variable as a variable. In Invention Example 6, the feed rate was 100, 150, 200 mm / mi.
After cutting to n, there was little vibration and the cutting could be continued. It was broken at a feed rate of 250. Comparative Example 7
Although a cutting test was started at a feed rate of 50 mm / min, mechanical vibration was severe and the breakage occurred. It had broken from a pile of chips. In SUS304 cutting, the chips tend to be bulky, so that the chip discharging property becomes more apparent.

Example 6 Using the end mills of Example 6 of the present invention and Comparative Example 7, a key was cut out from the end face of the pipe-shaped hub and subjected to a forming process. Workpiece is alloy steel SCr415 material,
The cutting conditions are a depth of 12 mm and a maximum width of 4 mm. In rough machining, the rotation speed is 1200 rpm and the feed rate is 25.
0m / min, the finishing process is 950rpm
m, and the feed rate was 180 m / min. The burr generation determines the tool life due to the processing of thin-walled pipes, but with the product of the present invention, it was possible to process 2300 pieces. Inventive Example 6 is
Although burrs were generated, they were slight and could be easily removed even after the above processing. In Comparative Example 7, hard burr that could not be removed was generated after processing 1000 times. Originally, in the case of the same cutting conditions, in the present invention example 6 with a small number of blades, the cutting amount per blade was large and load was applied to the cutting blade, and burrs were easily generated, but in this work, the cutting width was 4 mm. Since it is large, it is advantageous for chip disposal, and since the shapes of the blade groove and the arcuate blade are improved, a remarkable effect of several times or more compared with Comparative Example 7 was obtained.

Example 7 As Example 8 of the present invention, as shown in FIG. 9, a flat portion 11 was provided on the cutting edge portion and the mold was subjected to three-dimensional finishing. The work piece is prehardened die steel having a hardness of HRC40 and is used to reciprocally cut an inclined surface preprocessed by a ball end mill by scanning feed. The depth of cut is 1 mm or less, the pick feed is 2 mm, and the cutting conditions are rotation speed 8000 rpm and cutting speed 32.
0m / min, feed rate 800mm / min constant,
It cut using the water-soluble oil agent. Inventive Example 8 finished the work by cutting 16 m, but no wear was observed on the edge of the bottom blade in spite of the processing in which the cutting depth was not constant,
The processing accuracy was extremely good. 4 except for flat blades
Since the twist angle is 0 ° or more, the chips can be promptly discharged upward regardless of the feeding direction, and the chips are not caught in the cutting site. As a result, highly accurate processing can be realized. For the above processing, 30
A 4-twisted, cemented carbide end mill with a 4-degree twist, an end mill with a rake angle of 10 degrees, a groove depth of 1.6 mm, and an outer peripheral blade reaching the tip of the bottom blade.

Example 8 Using the end mills of the present invention example 6 and the comparative example 7, the invention was applied to wide side cutting of a mold insert. The work piece is a steel for pre-hardened mold with hardness HRC33, and a width of 0.5 is cut around the nest with a height of about 20 mm.
It was cut in mm. The cutting conditions are a rotation speed of 1200 rpm, a cutting speed of 38 m / min, and a feed speed of 200 mm / min. The length of the end mill cutting edge was 22 mm, but the cutting was performed with the overhang of the cutting edge set to 45 mm due to the workpiece. In Invention Example 6, chipping did not occur during cutting, and therefore, phenomena such as chattering and mechanical vibration that impair processing accuracy did not occur. After cutting continuously for 8 hours, there were no problems and excellent results were shown. In Comparative Example 7, chipping occurred during cutting and chattering increased, so that the product could not be completed. In end mill cutting, cutting is started from the tip of the end mill bottom blade, and the load from each direction concentrates on one point and acts on this portion. Endmills are generally prone to sharpening in this area, causing local damage. Since the end mill according to the present invention is provided with a flat blade on the blade edge, the load on the blade edge is dispersed and local damage is mitigated. Further, since the helix angle is large, in the case of side surface cutting, a plurality of cutting edges work to create a cutting surface at the same time, and a fine and flat surface can be obtained. If the helix angle is large, the blade groove will be geometrically small, but since it is a U-shaped blade groove, a chip space equivalent to that when the helix angle is loose can be secured, and the machinability can be further improved. Of.

Example 9 Using the end mills of Example 6 of the present invention and Comparative Example 7, a cylindrical hole having a diameter larger than the blade diameter was machined by helical cutting. Workpiece is structural carbon steel S50
It is a C-annealed material. A machining center was used for cutting, and high pressure air from the outside was used for the coolant. The processed hole has a diameter of 12 to 14 mm and a depth of 20 mm. Since the helical cutting is the processing of the closed area after the drilling, a two-blade end mill is usually used for this work. Here, as a comparative product, a cemented carbide end mill having the same size, a helix angle of 30 °, and a two-blade main body equipped with an air hole at the center of the main body was provided for helical cutting. Cutting conditions are tool rotation speed of 6000 rpm, and feed rate is 1200 mm / m at the end mill center in the revolution direction.
In, the current value required for cutting was measured by changing the axial advance amount for each revolution of 1 to 0.5 to 2.0 mm, and it was confirmed that the present invention product had a required current value lower by 20% or more. .
Further, the finished surface of the side surface of the machined hole was a good quality surface of 10 μmRy or less. Although the comparative end mill for exclusive use of helical cutting can improve the cutting efficiency, it is not easy to improve the surface roughness due to the relationship of the cutting edge rigidity. Since the product of the present invention has four blades, the load per blade is reduced, the chips are fine and sufficiently removed by the air supply from the outside, and the convex arcuate blade and the large watermelon angle engulf the chips. This is due to the fact that it exerts the action of discharging it without any action. Since the product of the present invention is not intended for exclusive use in helical cutting, but can be applied to side surfaces, deep grooves, etc., it can be seen that in consideration of this, it has excellent features that have not been achieved in the conventional range. .

[0035]

As described above, according to the present invention, in an end mill having a multi-blade strong twist, the shape of the cutting edge is improved. As a result, chips can be discharged smoothly, cutting vibration can be prevented, and the cutting performance can be improved. An excellent end mill that is suitable for heavy cutting such as cutting and has a long tool life and can also be used for finish cutting was obtained.

[Brief description of drawings]

FIG. 1 shows a front view of an embodiment of the present invention example.

FIG. 2 shows a cross section perpendicular to the blade of FIG.

FIG. 3 shows a cross section of a conventional example perpendicular to the blade.

FIG. 4 shows a front view of another embodiment of the present invention.

5 is an enlarged view of a main part of FIG.

FIG. 6 illustrates a processing mode.

FIG. 7 shows a front view of another embodiment of the present invention.

FIG. 8 is an enlarged view of a main part of FIG.

FIG. 9 shows a front view of another embodiment of the present invention.

[Explanation of symbols]

1 body 2 Outer peripheral cutting edge 3 helix angle 4 rake face 5 blade bottom 6 back 7 Third side 8 bottom blade 9 land width 10 Groove width 11 Flat part 12 Flat length 13 arc blade 14 Rake face of arc blade 15 Watermelon angle of the bottom blade

Claims (5)

[Claims] 1. A radius end mill having a twisted cutting edge on the outer circumference and an arcuate blade on the outer circumferential side of the bottom blade, wherein the shape of the groove groove in a cross section in the direction perpendicular to the cutting edge is from the rake face to the blade bottom, the back face. The shape curve from the cutting edge to the third surface of the adjacent cutting edge is substantially U-shaped, and the rake surface of the cutting edge faces the radial direction from the center of rotation within 5% or more of the blade diameter from the cutting edge. A radius end mill having a curved surface, and the rake face of the arcuate blade is a convex surface that is continuous along the cutting edge from the cutting edge to the bottom edge. 2. The radius end mill according to claim 1, wherein the cutting edge is 3 or more and the helix angle is 30 to 5 degrees.
Radius end mill, wherein the end mill has a core thickness of 0% to 60% to 75% of the blade diameter, and a bottom blade of the end mill has a water squeeze angle of 0.5 to 15 degrees. 3. The radius end mill according to claim 1 or 2, wherein the cutting edge has a rake angle of approximately 0 degrees. 4. The radius end mill according to claim 1, wherein the rake angle of the bottom blade is 0 in the axial direction.
Radius end mills characterized by a regular angle of 0 degrees or more. 5. The radius end mill according to any one of claims 1 to 4, wherein the land width of the cutting edge is 10% to 20% of the blade diameter in a cross-sectional view in a direction perpendicular to the blade. End mill.