JP5873345B2 - End mill - Google Patents

Description

  The present invention relates to an end mill suitable for cutting hard brittle materials such as cemented carbide, ceramics, glass, and high hardness steel materials.

In recent years, in the field of ultra-precision machining, when cutting high-precision dies and parts by cross-feeding, hard brittle materials such as cemented carbide, ceramics and glass, and high-hardness steel materials are used as work materials. Therefore, there is a demand for an end mill that performs high-precision finish cutting with high surface roughness.
When a work material made of such a hard and brittle material is cut with an end mill, a deep cut is not made when rough finishing is performed.

By the way, as an end mill having a high hardness blade, an end mill described in Patent Document 1 for cutting cast iron, hardened steel and the like has been proposed. This end mill is formed by forming a small-diameter columnar tongue on the tip surface of a substantially cylindrical tool body, and a braided portion having a substantially cylindrical shape and a cBN or PCD cutting edge is fitted to this tongue and brazed. Has been.
The blade is manufactured by sintering cBN or PCD powder into a solid annular body under high temperature and high pressure, or bonding the cBN or PCD layer to a substrate made of cemented carbide under high temperature and high pressure. It is manufactured by cutting into chips.
This makes it possible to manufacture a low-cost end mill with minimal risk of brazing joint breakage.

Special table 2002-504027 gazette

However, in the end mill described in Patent Document 1, cBN or PCD powder is sintered on the outer peripheral surface of a cylindrical blade made of cemented carbide brazed to the tongue of the tool body, or under high temperature and high pressure. Are combined to form a substantially dot-shaped blade portion. Using such an end mill, when cutting a hard brittle material such as cemented carbide, ceramics, or glass as a work material or a high-hardness steel material, the work material is hard. Due to the short life, high-precision machining has been difficult for a long time.
In addition, if the end mill has an extremely fine outer diameter such as 2 mm or less, or 0.5 mm or less, the cutting resistance increases even if the above-described cylindrical or columnar blade portions are formed. However, there are also disadvantages that ultrafine processing is difficult and breakage tends to occur.

  The present invention has been made in view of such circumstances, and an object of the present invention is to provide a long-life end mill that can perform high-precision processing even if the work material is a hard brittle material or a high hardness steel material. .

In the end mill according to the present invention, the tool body has a substantially hexagonal axial cross section, and two side surfaces facing each other at the tip are formed by a tapered surface and a first side each having a diameter reduced toward the tip surface, Two outer peripheral blades are formed facing the corner of the tip of the tool body, a rake face having a negative rake angle is formed on the front side in the rotational direction of the outer peripheral blade, and the rotational direction of the outer peripheral blade A clearance surface having a positive clearance angle is formed on the rear side , a substantially hexagonal flat surface including the apexes of the two outer peripheral blades is formed on the tip surface, and the flat surface is formed on the two outer peripheral blades. A groove is formed that is divided in a direction intersecting the diagonal of the maximum length connecting the apexes and includes the rotation axis of the tool body, and the maximum outer diameter D between the two outer peripheral blades is 0.5 mm or less. There, bottom intersecting ridgeline portions between the divided side of the flat surface and the tool body Forming a bottom blade of the intersection ridge line between the first bottom cutting edge and the flat surface and the first side surface forming the intersection ridge line between the rake face and the flat surface from the apex of the outer peripheral edge said peripheral cutting edge The second bottom blade is formed in a convex shape .
The end mill according to the present invention cuts the side wall of the work material with two outer peripheral blades by laterally feeding while rotating, and finishes the processed surface with the bottom blade, and the rake angle of the outer peripheral blade is negative. Since it is a corner, it is possible to cut a thin chip and obtain a good finished surface with a bottom blade, and has a high tool rigidity and a long life. The chips cut by the outer peripheral blade travel on the side rake face and are sent to the base end side. Also, a finished surface can be obtained by finishing the processed surface of the work material with the bottom blade and rubbing the processed surface with a flat surface formed on the flank. In addition, the cutting resistance can be reduced because the concave grooves are formed in the region including the rotation axis of the flat surface when cutting the work material.

Moreover, the maximum outer diameter dimension D between the two outer peripheral blades is 0.5 mm or less .
Since the end mill according to the present invention has a cutting edge portion having a flat surface with two outer peripheral blades facing each other at the tip portion, the maximum outer diameter is 0.5 mm or less, so that it can be cut as an extremely small end mill. It is possible to perform ultrafine processing of materials with high accuracy. On the other hand, if the maximum outer diameter is larger than 0.5 mm, the cutting resistance may be greatly damaged.

The maximum outer diameter dimension between the two outer peripheral blades is D, the outer peripheral blades are formed at the corners protruding outward, and the length L connecting the apex of one outer peripheral blade and the groove on the flat surface is 0. It is preferably set in the range of 1D to 0.45D.
If the length L is in the range of 0.1D to 0.45D, tool wear, cutting resistance and chipping of the flat surface can be suppressed, and the tool life can be ensured. If the length L is less than 0.1D, the tool wears. There is a risk that the tool life will be remarkably reduced and a flat surface will be lost. If it is larger than 0.45D, the cutting resistance will increase and the processing surface may be deteriorated.

Further, the maximum outer diameter dimension between the two outer peripheral blades is D, and the width of the bottom blade in the direction perpendicular to the diagonal line connecting the apexes of the two outer peripheral blades (the width of the flat surface) e at the tip of the tool body. Is preferably set in the range of 1 / 4D to 1 / 2D.
If the width e of the bottom blade is less than 1 / 4D, the tool rigidity may be significantly reduced and the chipping may occur. If the width e exceeds 1 / 2D, the cutting resistance may increase, leading to tool chipping and deterioration of the machined surface. .

The maximum outer diameter dimension between the two outer peripheral blades is D, and the length of the side surface in the rotational axis direction following the bottom blade in the direction perpendicular to the diagonal line connecting the apexes of the two outer peripheral blades at the tip of the tool body It is preferable that the depth (bottom blade depth) d is set in a range of 0.05D to 0.5D.
If the length d of the bottom blade is smaller than 0.05D, the chip pocket may become extremely small and there is a risk of chipping due to chip clogging. If the length d is larger than 0.5D, the tool rigidity will be significantly reduced and chipping will occur. May occur.

Moreover, it is preferable that the maximum outer diameter dimension between the two outer peripheral blades is D, and the depth c of the concave groove in the rotation axis direction is set in a range of 0.05D to 0.5D.
If the depth c of the concave groove is smaller than 0.05D, the chip pocket due to the concave groove may become extremely small, and chipping may occur, and if the depth c is larger than 0.5D, the tool rigidity is significantly reduced. There is a risk of loss.

Further, the rake angle a of the rake face of the outer peripheral blade is preferably set in the range of −30 ° to −80 °.
If the rake angle a is smaller than -30 °, the rigidity of the outer peripheral blade may be reduced, and the chip may be damaged. If the rake angle a is larger than -80 °, the chip pocket becomes extremely small, resulting in chip clogging. May cause defects.

Moreover, it is preferable that the clearance angle b of the flank face of the outer peripheral blade is set in a range of 5 ° to 60 °.
If the clearance angle b is smaller than 5 °, the clearance amount becomes extremely small and the cutting surface is rubbed and deteriorated. If the clearance angle b is larger than 60 °, the rigidity of the cutting edge is remarkably lowered and there is a possibility of causing a defect.

Moreover, it is preferable that the outer peripheral blade is formed with a round land or a chamfered flat surface.
In this case, the cutting ability of the outer peripheral blade can be ensured and the tool rigidity and the cutting blade life can be maintained long. Moreover, the width of the round land or the flat surface is preferably set in the range of 0.002 to 0.03 mm, and within these ranges, the above-described characteristics can be reliably ensured.

In addition, the angle f at which the groove extends is set in a range of 0 ° to 30 ° with reference to an imaginary line perpendicular to a diagonal line connecting the apexes of the two outer peripheral blades at the tip of the tool body. Is preferred.
When the range of the angle f of the groove is the above-described range, the groove is formed in the rotation direction of the tool body, so that the cutting resistance by the bottom blade is reduced and the chip discharging property is good. is there.

According to the end mill of the present invention, two outer peripheral blades are formed opposite to the flat surface corner of the tip of the tool body, and a rake face having a negative rake angle is formed on the front side in the rotational direction of the outer peripheral blade. The flat surface is divided into grooves including the rotation axis of the tool body, and a bottom blade is formed at the intersection ridge line between the divided flat surface and the side surface of the tool body. Even if it is a fine diameter, the outer peripheral cutting can be performed with the opposing outer peripheral blade and the machining surface can be finished with the bottom blade. The cutting with the outer peripheral blade is relatively shallow and the chips pass through the side rake face. Escape to the end and finish with high precision by cutting with the bottom blade. In addition, since the rigidity of the outer peripheral blade and the bottom blade is large and the strength is high, chipping and wear of the cutting edge are prevented, and the tool rigidity is high and the life is long.
In addition, since the flat surface at the tip of the tool body is used as the flank surface of the bottom blade, the cutting edge of the bottom blade is large, and the machining surface is rubbed with the flat surface that forms the flank surface when cutting with the bottom blade, resulting in higher finishing accuracy. Even if the work material is a hard brittle material or a high hardness steel material, a highly precise finishing process can be performed with a relatively shallow cutting process and a long life can be obtained.

It is a bottom view of the end mill by the embodiment of the present invention. It is a principal part side view of the end mill shown in FIG. It is a principal part side view of the direction orthogonal to the side surface of the end mill shown in FIG. It is a principal part front end view of the corner | angular part which shows the 1st modification of an outer periphery blade. It is a bottom view which shows the 2nd modification of the front-end | tip part of a blade edge | tip part.

Hereinafter, an embodiment of the present invention will be described in detail with reference to FIGS. 1 to 3.
1 and 2, in the end mill 1 according to the present embodiment, the tool body 2 having a shank member has a cross section orthogonal to the axis, for example, a substantially hexagonal shape, here a regular hexagonal shape, and the blade portion 3 is fixed to the tip side thereof. Has been. The blade portion 3 has a blade edge portion 3a which is gradually reduced in diameter in a hexagonal cross section from the proximal end side toward the distal end side and is enlarged by one step near the distal end. The blade portion 3 is included in the tool body 2. Further, the tool body 2 is rotatable around the rotation axis O at the center.
The tool body 2 is made of, for example, a cemented carbide, and the blade portion 3 is fixed to the front end side of the shank member by integral molding (simultaneous sintering). Alternatively, the tool body 2 may be formed by brazing the blade portion 3 to the tip side of the shank member. The blade 3 is obtained by integrally sintering a cBN sintered body, a diamond sintered body (PCD), or the like, or a base material such as cemented carbide with a general hard film, diamond coating or diamond electrodeposition. Is used. In addition, you may integrally form the tool main body 2 whole including the blade part 3 with one of the said raw materials.
In this embodiment, the blade part 3 consists of a diamond sintered compact (PCD).

The blade portion 3 formed on the distal end side of the tool body 2 forms a hexagonal column shape by the six side surfaces 10, and its axial orthogonal cross-sectional shape is a substantially regular hexagon. The distal end side of the blade part 3 is an enlarged blade edge part 3 a, and two ridge lines are provided at opposite corners of the outer peripheral surface, which are the outer peripheral blades 6. As shown in FIG. 2, the outer peripheral blade 6 is formed in a straight shape or a back taper shape that forms a straight line parallel to the rotation axis O.
Then, on the bottom surface of the blade edge portion 3a shown in FIG. 1, a deformed substantially hexagonal flat surface having a diagonal line M connecting the apexes 6a, which are the tip edges of the two opposing outer peripheral blades 6, with the maximum length being narrow on both sides. 7 is formed. The distance D of the diagonal line M connecting the vertices 6a of the two opposing outer peripheral blades 6 is D, and this distance D forms the maximum outer diameter of the cutting edge portion 3a formed by the rotation trajectories of the two outer peripheral blades 6. Further, the side surface 10 provided in front of the outer peripheral blade 6 in the rotational direction constitutes a rake surface 14.

  Further, the two sides 10 across the diagonal M of the flat surface 7 are substantially the same along the rotation axis O with the two opposite side surfaces 10 of the blade edge portion 3a having the side surfaces 10 of a regular hexagonal cross section as shown in FIGS. A first side face 8 is formed by cutting a predetermined length d in parallel with a width, and further, the base end side of the first side face 8 is cut so as to be tapered and connected to a substantially regular hexagonal side face 10. A tapered surface 9 is formed. Each of the two side surfaces adjacent to the first side surface 8 and the tapered surface 9 is the hexagonal columnar side surface 10 described above.

  Next, in the bottom surface of the blade edge portion 3a shown in FIG. 1, the flat surface 7 having a narrow deformed substantially hexagonal shape was cut in the center in the longitudinal direction, including the rotation axis O, in a direction substantially orthogonal to the diagonal line M. A concave groove 12 is formed. Since the rotation speed is low and the cutting resistance is high in the vicinity of the rotation axis O of the flat surface 7 at the tip of the cutting edge portion 3a, the cutting resistance during processing is suppressed by cutting this region to form the concave groove 12. Further, when chips generated by cutting with the outer peripheral blade 6 or the bottom blade 13 described later flow into the concave groove 12, the chips can be released to the rear side in the rotational direction through the concave groove 12. Therefore, the groove 12 also serves as a chip pocket.

  The intersecting ridge line between the flat surface 7 and the side surface on the front side in the rotational direction of the blade portion 3 from the apex 6a of the outer peripheral blade 6 is a bottom blade 13 formed on two sides of the flat surface 7, and the bottom blade 13 is the outer periphery. Extending from the apex 6 a of the blade 6, the first bottom blade 13 a at the intersection ridge line portion between the flat surface 7 and the side surface 10 and the second bottom blade 13 b at the intersection ridge line portion between the flat surface 7 and the first side surface 8 are convex. Is formed. Therefore, the side surface 10 and the first side surface 8 are rake surfaces of the bottom blade 13.

The side surface 10 on the front side in the rotation direction of the blade portion 3 with respect to the outer peripheral blade 6 is a rake face 14, and the rake angle a of the outer peripheral blade 6 is set to a negative angle in the range of, for example, -30 ° to -80 °. .
Here, if the rake angle a is smaller than −30 °, the rigidity of the cutting edge may be remarkably lowered, and there is a risk of chipping. If the negative angle is larger than −80 °, a larger negative angle results in a decrease in sharpness. There is a possibility that the chip pocket made of the rake face 14 becomes extremely small, resulting in chipping due to chip clogging. The rake angle a is more preferably in the range of −45 ° to −60 °, and the best result is obtained within this range.

  Further, the side surface 10 on the rear side in the rotational direction of the blade portion 3 with respect to the outer peripheral blade 6 is a flank 15 and the flank angle b is set to a positive angle in the range of 5 ° to 60 °. Here, if the clearance angle b is smaller than 5 °, the clearance amount becomes extremely small and the cutting surface is rubbed and deteriorated, and if the clearance angle b is larger than 60 °, the cutting edge rigidity is remarkably lowered and the chipping is lost. May be caused. The clearance angle b is more preferably in the range of 30 ° to 45 °, and the best result is obtained within this range.

2, the first side surface 8 and the side surface 10 form a rake face with respect to the bottom blade 13, and the flat surface 7 divided by the concave groove 12 is a relief of the bottom blade 13. Configure the surface. The flat surface 7 is greatly related to the receding of the surface due to wear and the properties of the machined surface, and the width L from the apex 6a to the groove 12 in the side view is set in the range of 0.1D to 0.45D. Therefore, a good machined surface can be obtained. When the width L is within this range, the cutting edge strength is high and wear of the flat surface 7 is suppressed, and a good finished surface can be obtained.
Here, when the width L is smaller than 0.1D, the cutting edge strength is too small and easily breaks, and when it is larger than 0.45D, there is a disadvantage that the cutting resistance is large.

  In FIG. 2, the depth c in the direction of the rotation axis O of the groove 12 that divides the flat surface 7 at the tip of the blade edge 3 a and partitions the bottom blade 13 is set in the range of 0.05D to 0.5D. Has been. If the depth c of the concave groove 12 is smaller than 0.05D, chips are likely to be clogged, and the tool body 2 may be lost due to clogging. On the other hand, if the depth c exceeds 0.5D, the tool rigidity is remarkably lowered, and there is a possibility of causing a defect.

  In FIG. 3, the flat surface 7 is formed in a columnar shape with the first side surfaces 8 facing each other so as to have substantially the same width by a predetermined distance d in the direction of the rotation axis O. This predetermined distance d is defined as the depth d of the bottom blade 13 on the flat surface 7. The depth d of the bottom blade 13 is set in the range of 0.05D to 0.5D. Here, if the depth d of the bottom blade 13 is smaller than 0.05D, the chip pocket due to the rake face 14 may become extremely small and a chipping may occur, and if it is larger than 0.5D, the tool rigidity is remarkably increased. There is a risk of lowering and loss.

  Moreover, in FIG. 1, the width e of the bottom blade 13 which is the width of the flat surface 7 is set in a range of 1 / 4D to 1 / 2D. If the width e is smaller than 1 / 4D, the rigidity of the tool is remarkably lowered and a chipping may occur. If the width e is larger than 1 / 2D, the cutting surface may be increased due to an increase in cutting resistance and the cutting surface may be deteriorated.

In the end mill 1 according to the present embodiment, the outer diameter D of the two outer peripheral blades 6 facing each other at the cutting edge portion 3a is preferably 0.5 mm or less, for example, 50 μm or more. Therefore, the end mill 1 according to the present embodiment is an ultra-fine diameter end mill having two blades, and the bottom surface of the blade tip portion 3a is formed on the flat surface 7 and a pair of outer peripheral blades 6 and bottom blades 13 respectively facing the outer peripheral surface. It has a substantially straight line shape or a columnar shape like a flat-blade screwdriver.
Although it is possible to form such an end mill 1 in a shape having an outer diameter D exceeding 0.5 mm, the outer diameter D is preferably 0.5 mm or less in order to suppress cutting resistance.
In the end mill 1, if the outer diameter D is in the range of 0.5 mm to 50 μm, it is possible to process an extremely fine shape with high accuracy. On the other hand, if the outer diameter D of the end mill 1 is larger than 0.5 mm due to the shape of the cutting edge portion 3a having a substantially linear column shape, the resistance at the time of cutting increases, and if the outer diameter D is smaller than 50 μm, the cutting edge portion 3a is manufactured. It becomes difficult.

The end mill 1 according to the present embodiment has the above-described configuration, and the operation thereof will be described next.
The end mill 1 according to the present embodiment is used to cut into a work material made of a hard brittle material such as cemented carbide, ceramics, or glass, or a high-hardness steel material, and perform transverse feed processing.
At the time of cutting, if the work material is, for example, a hard and brittle material, the end mill 1 makes a thin cut of, for example, several nanometers or nanometers with a pair of opposed outer peripheral blades 6 formed on the cutting edge portion 3a, and the rotation axis O Feeds horizontally while rotating around. Then, shoulder cutting can be performed by cutting shallowly with the outer peripheral edge 6 of the end mill 1. The main cutting process is performed by the two outer peripheral blades 6 facing each other, and the finishing process is performed at the apex 6 a of the outer peripheral blade 6.
The thin-layer chips cut by the outer peripheral blade 6 are sent to the rake face 14 formed by the side surface 10 on the front side in the rotational direction of the outer peripheral blade 6 and further sent to the first side surface 8 and the tapered surface 9 on the adjacent side surfaces. It is sent out to the base end side of the tool body 2. Further, some chips enter the concave groove 12 from the first side surface 8 and are discharged from the first side surface 8 side on the opposite side to the proximal end side.

Then, by performing a slight lateral feed while rotating the tool body 2 around the rotation axis O, the machining surface of the work material is finished by the bottom blade 13 formed on the flat surface 7 which is the bottom surface of the blade edge portion 3a. . Since the flat surface 7 which is the flank of the bottom blade 13 is flat, the processed surface can be thinly cut with the bottom blade 13 and then rubbed and leveled with the flat surface 7 for finishing with high accuracy.
A thin layer of chips cut by the first bottom blade 13a of the bottom blade 13 is sent out from the side surface 10 which is a rake face to the base end side through the tapered surface 9, and is discharged to the base end side of the tool body 2. . Further, the thin layer of chips cut by the second bottom blade 13b is sent out from the first side surface 8 which is a rake face to the base end side through the tapered surface 9, and is discharged.
At this time, when the bottom blade 13 is a diamond sintered body obtained by sintering diamond having a fine particle diameter of, for example, 0.5 to 1.0 μm or other materials described above, the work material is a hard brittle material or a high Even a hard steel material is finished with a nanometer-size processing accuracy of about 1 nm or 2 nm.

As described above, the end mill 1 according to the present embodiment has the substantially straight columnar cutting edge portion 3a, and is shoulder-cut by the pair of outer peripheral blades 6 formed at the opposite corners and divided by the concave groove 12. In addition, the tool body is formed even if the work material is a hard brittle material, a high-hardness steel material, glass or the like because the bottom blade 13 of the flat portion 7 is used for shallow cutting and is finished by rubbing with the flat portion 7. The cutting in the axial direction of 2 is shallow, the shoulder of the work material by the outer peripheral edge 6 is smooth, and the work surface of the work material in the transverse feed direction can be finished with a fine and high processing accuracy of nanometer size.
In addition, since the bottom blade 13 is formed by being bent convexly by the first bottom blade 13a and the second bottom blade 13b, the cutting resistance is small, and also from this point, the surface roughness of the processed surface in the lateral feed direction is small. small.

  Further, the end mill 1 according to the present embodiment has high strength when, for example, a diamond sintered body (PCD) is used as the material of the tool body 2, and the outer peripheral edge 6 is a corner portion of the flat portion 7 having a narrow hexagonal shape. The bottom blade 13 has a high rigidity because the flat surface 7 that forms the flank is a flat negative angle, and therefore has a large blade edge angle, a long blade edge life, and the work material is a hard and brittle material. Even high-strength steel materials can be finely processed with a precision of nanometer size.

As mentioned above, although the end mill 1 by embodiment of this invention was demonstrated, this invention is not limited to such embodiment, It can say that a various form and aspect can be employ | adopted within the range which does not deviate from the meaning of this invention. Not too long.
For example, the cross-sectional shape of the concave groove 12 is not necessarily limited to a substantially U-shape, and may be a cross-sectional shape such as a substantially arc shape, a substantially V shape, a rectangular shape such as a substantially rectangular shape or a trapezoidal shape.

Moreover, in the end mill 1 by this embodiment, although the blade angle | corner of the outer periphery blade 6 formed in the corner | angular part of the blade edge | tip part 3a was formed in the sharp angle which side surfaces 10 cross | intersect, it replaces with this and is a 1st modification. As shown in FIG. 4A, the outer peripheral edge 6 may be formed on the round land 17. Or you may form in the flat surface 18, as shown in FIG.4 (b). By forming the blade with the round land 17 or the flat surface 18 at the corner of the tip of the outer peripheral blade 6, it is possible to prevent the chipping when roughing.
In these cases, the width t of the round land 17 or the flat surface 18 is set in the range of 0.002 to 0.03 mm. If the width t is set within this range, the sharpness of the outer peripheral blade 6 can be secured and the strength of the blade edge can be improved.
On the other hand, if the width t is smaller than 0.002 mm, a remarkable effect cannot be obtained, and if it is larger than 0.03 mm, abnormal wear may occur.

Moreover, the concave groove 12 which divides | segments the flat surface 7 in the bottom face of the blade edge | tip part 3a of the end mill 1 by this invention is formed in the direction orthogonal to the diagonal M which connects the vertex 6a of the outer periphery blade 6 in the above-mentioned embodiment, The center line of the concave groove 12 is formed so as to be a virtual line N that is orthogonal to the diagonal line M and passes through the rotation axis O, for example. However, in the second modification of the present invention, the concave groove 12 is set to an angle f = 0 ° to 30 ° with respect to the virtual line N. The case where the angle f = 0 ° is the configuration shown in FIG.
In this case, the center line of the concave groove 12 is preferably set at an angle f or less through the rotation axis O, but may be off the rotation axis O.

If the range of the angle f of the concave groove 12 is the range described above, the concave groove 12 is formed in the rotational direction of the blade edge portion 3a. The discharge performance of the is improved.
On the other hand, when the angle f of the concave groove 12 is smaller than 0 °, the second bottom blade 13b of the bottom blade 13 becomes longer, and the cutting resistance is reduced and the chip discharging performance is remarkably lowered. Further, if the angle f is larger than 30 °, the second bottom blade 13b becomes extremely short, and there is a drawback that the tool rigidity is lowered.
Further, the width L from the apex 6 a of the outer peripheral edge 6 to the groove 12 in the side view shown in FIG. 2 refers to the length from the apex 6 a to the intersection of the diagonal M and the groove 12.

Further, on the flat surface 7, a C-face blade or an R-blade may be formed at a corner portion where the outer peripheral blade 6 and the bottom blade 13 intersect. In this case, it can be used for roughing and for preventing breakage. .
Further, in the above-described embodiment, in the end mill 1, the undercut portions such as the blade portion 3 on the base end side of the blade edge portion 3a and the tool body 2 are not limited to a hexagonal cross section, and may have an appropriate cross sectional shape such as a columnar shape. Can be adopted.
Further, the side surface 10 and the first side surface 8 forming the rake face of the bottom blade 13 of the blade edge portion 3a are formed in a straight shape, that is, a negative angle of 90 ° as shown in FIG. For example, the rake angle of the bottom blade 13 may be inclined so as to be a negative angle larger than 90 °. Or you may make it incline so that the rake angle of the bottom blade 13 may become a regular angle smaller than 90 degrees.

DESCRIPTION OF SYMBOLS 1 End mill 2 Tool main body 3 Blade part 3a Cutting edge part 6 Outer peripheral blade 7 Flat surface 8 First side surface 9 Tapered surface 10 Side surface 12 Groove 13 Bottom blade 14 Rake surface 15 Relief surface 17 Round land 18 Flat surface

Claims (8)

The tool body has a substantially hexagonal axial cross section, and two side surfaces facing each other at the tip are formed with a tapered surface and a first side each having a diameter reduced toward the tip surface,
Two outer peripheral blades are formed facing each other at the corner of the tip of the tool body,
Forming a rake face having a negative rake angle on the front side in the rotational direction of the outer peripheral blade, and forming a flank face having a positive flank angle on the rear side in the rotational direction of the outer peripheral blade;
A flat surface having a substantially hexagonal shape including the vertices of the two outer peripheral blades is formed on the tip surface, and the flat surface is divided in a direction intersecting with a diagonal of the maximum length connecting the apexes of the two outer peripheral blades. And a groove containing the rotation axis of the tool body is formed ,
The maximum outer diameter D between the two outer peripheral blades is 0.5 mm or less,
A bottom blade is formed at the intersecting ridge line portion between the divided flat surface and the side surface of the tool body, and the bottom blade forms an intersecting ridge line portion between the flat surface and the rake face of the outer peripheral blade from the apex of the outer peripheral blade. An end mill characterized in that a first bottom blade, a second bottom blade forming an intersecting ridge line portion between the flat surface and the first side surface are formed in a convex shape . The maximum outer diameter dimension between the two outer peripheral blades is D, the outer peripheral blade is formed at a corner protruding outward, and the length L connecting the apex of the one outer peripheral blade and the groove on the flat surface is The end mill according to claim 1 , wherein the end mill is set in a range of 0.1D to 0.45D. The maximum outer diameter dimension between the two outer peripheral blades is D, and the width e of the bottom blade in the direction perpendicular to the diagonal line connecting the apexes of the two outer peripheral blades is 1 / 4D at the tip of the tool body. The end mill according to claim 1 or 2, which is set in a range of ~ 1 / 2D. The maximum outer diameter dimension between the two outer peripheral blades is D, and at the tip of the tool body, the side surface in the rotational axis direction following the bottom blade in the direction perpendicular to the diagonal line connecting the apexes of the two outer peripheral blades The end mill described in any one of Claims 1 thru | or 3 by which the length d of is set to the range of 0.05D-0.5D. Examples D to the maximum outer diameter dimension between the two peripheral cutting edge of any of claims 1 to 4 the depth c of the groove of the rotation axis direction is set in a range of 0.05D～0.5D 1 End mill described in the section. 6. The end mill according to claim 1, wherein a rake angle a of the rake face of the outer peripheral blade is set in a range of −30 ° to −80 °. The end mill described in any one of Claims 1 thru | or 6 with which the clearance angle b of the flank of the said outer periphery blade is set to the range of 5 degrees-60 degrees. At the tip of the tool body, the angle f at which the groove extends is set in a range of 0 ° to 30 ° with reference to an imaginary line in a direction perpendicular to a diagonal line connecting the apexes of the two outer peripheral blades. The end mill according to any one of claims 1 to 7 .

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