JP2000288829A - End mill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To secure favorable chip discharging performance without damaging tool rigidity by providing a groove base of a chip discharge groove connected to a rake face of a cutting blade with a linear part, a part of which is clamped within a specified range of a width to the radius of an end mill and has a length of a specified value or more. SOLUTION: A groove base 19 of a chip discharge groove 13 connected to a rake face of a cutting blade 16 is formed extending linearly from the rake face, and a linear part 20 is disposed in a section along the inclined flat surface of the groove base 19. In this arrangement, the linear part 20 is a part where the groove base 19 is within a range of a band of a width W1 of 0.1 R to the distance from the axis O of a tool main body 11 to the cutting blade 16 in the section intersecting perpendicularly to the axis O, that is, the end mill radius R. The part is extended from the inner peripheral end of the rake face to reach the intersecting part between flank 15 of the next cutting blade 16 adjacent to the tool rotating direction T side of the cutting blade 16 and the groove base 19, that is, a heel part 21, and the length L thereof is 0.7 R or more to the radius R of the end mill.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION The present invention relates to a cutting edge which is spirally twisted around the axis at a peripheral edge of a chip discharge groove formed on the outer periphery of a tool body rotated about the axis. End mill.

[0002]

2. Description of the Related Art In such grooving and shoulder milling by an end mill, a cutting portion cut by a cutting blade is a wall surface on the back side of a groove formed in a workpiece, and its periphery is a groove. Since it becomes a closed portion surrounded by the side wall surface, how to smoothly discharge the chips generated by the cutting blade from the chip discharge groove at the time of cutting is an important issue in performing efficient cutting. . Here, Minoru Arai, "Basics and Application of Chip Control" (December 20, 1990, published by The Nikkan Kogyo Shimbun) states that the cutting blades are spirally twisted or inclined as described above. In this case, it is shown that the chips flow out not in a direction perpendicular to the cutting edge but in a direction in which the cutting edge is inclined to a side where the cutting edge is inclined by a predetermined outflow angle η, and this outflow angle η is η = K × i (where k is a constant, which is 1.0 according to Stabler, and 0.6 to 0. 0, for example, when the workpiece is carbon steel (S45C) according to Spaans.
7, i is the inclination angle of the cutting edge, and when the cutting edge is twisted like the end mill, it is indicated as the angle of twist of the cutting edge with respect to the axis of the tool body.

[0005] FIG. 5 shows a substantially cylindrical tool body 1 on the outer periphery thereof.
Four chip discharge grooves 2 twisted around the axis O of the tool body 1 are formed at equal intervals in the circumferential direction, and face the tool rotation direction T, which is a rake face 3 of these chip discharge grooves 2. Conventionally, a cutting edge 4 that is spirally twisted around the axis O so as to be directed toward the tool rotation direction T toward the tool tip side (the lower side in FIG. 5) is formed on the outer peripheral side edge of the wall surface. In the general four-flute end mill, the first cutting edge 4
2 shows the rake face 3 connected thereto and the groove bottom face 5 of the chip discharge groove 2 further connected to the rake face 3. The symbol P in FIG.
The cutting edge 4 passes through a point Q on the cutting edge 4 and is perpendicular to a plane S including the point Q and the axis O, and passes through the point Q on a tangent plane of the rake face 3 at the point Q. This is an inclined plane including a straight line inclined in the direction of the outflow angle η with respect to the direction perpendicular to the ridge line. It flows out to the bottom surface 5 and is discharged.

[0004]

Here, the inclination angle δ of the inclined plane P with respect to a plane orthogonal to the axis O is as follows.

[0005]

(Equation 2)

[0006] However, in this equation, r _r is a radial rake angle in a cross section perpendicular to the cutting edge 4, in the case of a square end mill is a true rake angle of the cutting edge 4,
Η is the above-mentioned outflow angle, η = k × i, and i is the torsion angle of the cutting edge 4 with respect to the axis O. Note that the constant k
Is set to 0.5 to 1.0 in consideration of a workpiece other than carbon steel.

FIG. 6 is a cross-sectional view of the tool body 1 of the conventional four-flute end mill along the inclined plane P. As shown in FIG. Chip discharge groove 2 connected to rake face 3 via rake face 3
Is formed so as to have a convex curved surface bulging toward the outer periphery of the tool in a cross section along the inclined plane P from which the chips flow out, so that the chips flowing out along the groove bottom surface 5 The bottom surface 5 of the groove collides with the swollen portion and is liable to be clogged, so that smooth chip discharge is hindered. On the other hand, if the cross-sectional area of the chip discharge groove 2 is increased in order to secure the chip discharge performance, the cross-sectional area and the second moment of area of the tool body 1 are reduced, and the tool rigidity is impaired. Occasionally, vibrations are likely to occur in the tool body 1, which may cause a significant deterioration in cutting accuracy and tool life.

The present invention has been made in view of such circumstances, and an object of the present invention is to provide an end mill capable of securing good chip discharge without impairing tool rigidity.

[0009]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems and to achieve such an object, the present invention provides a chip discharge groove formed on an outer periphery of a substantially cylindrical tool body rotated around an axis. An end mill, wherein a cutting edge twisted around the axis is formed at an outer peripheral edge of a groove wall surface which is a rake face facing the tool rotation direction side of the chip discharge groove. A cross section along an inclined plane that passes through the above one point, is perpendicular to a plane including the one point and the axis, and is inclined at an inclination angle δ given by the following equation with respect to a plane orthogonal to the axis. The length of the part where the groove bottom surface of the chip discharge groove continuous with the rake face of the cutting edge is sandwiched within a range of 0.1R or less with respect to the end mill radius R from the axis to the cutting edge has a length of 0.7R. It is characterized by including the linear portion as described above.

[0010]

(Equation 3)

Therefore, in the end mill having such a configuration, in the cross section of the tool body along the inclined plane extending in the direction of the outflow angle η at which the chips flow, the end mill radius R is provided on the bottom surface of the chip discharge groove. Width 0.1
Since the linear portion included in the range within R is secured to 0.7R or more, the chip can be smoothly discharged without clogging of the chip, and the sectional area and the second moment of area of the tool body are reduced. Sufficient tool rigidity can be ensured while preventing damage to others.

Here, the length of the linear portion in the cross section along the inclined plane is shorter as the length is less than 0.7R, that is, in the cross section, the groove bottom surface has a length of 0.7R and a width of 0.1R or less. If the undulation is too large to fit within the range,
There is a possibility that chips may be clogged at a portion where the groove bottom surface is convex, and tool rigidity may be impaired at a portion where the groove bottom is concave. Note that the lower limit of the width of the linear portion may be 0, that is, the linear portion may be formed in a linear shape. In addition, the upper limit of the length of the linear portion is preferably as long as it is 0.7R or more. However, in practice, the flank of the next cutting edge is provided on the side of the groove bottom surface in the tool rotation direction. For example, in the above-mentioned four-flute end mill, the upper limit of the length of the linear portion is about 1.5R because the clearance must be formed at a clearance angle. Furthermore, in order to make the linear portion flatter on the inclined plane and to ensure smoother chip discharge performance and sufficient tool rigidity, the linear portion is 0.1 mm to the end mill radius R. It is desirable that the portion included in the range of 05R or less be formed to have a length of 0.7R or more.

[0013]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS. In this embodiment, the tool main body 11 is formed of a hard material such as a cemented carbide in a substantially cylindrical shape as shown in FIGS. 1 and 2, and a rear end portion thereof is formed as a shank portion 12. Are formed at regular intervals in the circumferential direction with four strips of chip discharge grooves 13 twisting rearward in the tool rotation direction T about the axis O of the tool body 11 from the front end to the rear end side of the tool body 11. Have been.

The wall surface of each of the chip discharge grooves 13 facing the tool rotation direction T is a rake face 14, and the outer peripheral side ridge, ie, the rake face 14 and the rake face 14
A cutting edge 16 is formed at the intersection ridge line portion with the flank 15 continuous with the cutting edge 16 so as to be spirally twisted around the axis O. In addition,
The rake face 14 is provided at the tip of each of the chip discharge grooves 13.
A bottom blade 18 is formed at the intersection ridge line between the rake face and the tip flank 17 of the tool main body 11 so as to extend from the axis O to the outer peripheral side of the tool along the radial direction as shown in FIG. As shown in FIG. 1, the cutting edge 16 has a square corner with the cutting blade 16, and has a so-called square end mill configuration.

FIG. 3 shows the cutting blades 16 formed in the four chip discharge grooves 13 in this embodiment.
One of the cutting edges 16 and the rake face 14 connected thereto
3 and a bottom surface 19 of the chip discharge groove 13 further connected to the rake face 14 on the side of the tool rotation direction T. In FIG.
In the direction perpendicular to the plane S including the point Q and the axis O and passing through the point Q on the tangent plane of the rake face 14 at the point Q and perpendicular to the ridge line of the cutting edge 16. An inclined plane including a straight line inclined in the direction of the angle η;
Is inclined at an inclination angle δ given by the following equation with respect to a plane orthogonal to the axis O as shown in FIG.

[0016]

(Equation 4)

[0017] However, in this equation, _r r is the cutting edge 16
Is the radial rake angle in the cross section perpendicular to the angle, and in the case of a square end mill, it is the true rake angle of the cutting edge 16, and the outflow angle η is given by η = k × i, and i is the cutting edge 1
6 is a twist angle with respect to the axis O. Further, the constant k is in the range of 0.5 to 1.0. For example, the radial rake angle r _r is 8 °, the twist angle i is 45 °, and the constant k is 0.6.
If the outflow angle η is 27 °, the inclination angle δ is about 16.3 °. By the way, the radial rake angle r _r
Is −10 ° to + 15 °, the torsion angle i is 20 ° to 70 °, and the constant k is 0.5 to 1.0, the inclination angle δ is 4.8 °.
４５45 °. In the case the radial rake angle r _r The following table 1 is 8 ° and 0 °, the twist angle i is 30 ° and 45
In the case of °, the outflow angle η and the inclination angle δ in each case where the constant k is 0.5 and 1.0 are summarized.

[0018]

[Table 1]

FIG. 4 shows a cross section of the tool body 11 along the inclined plane P inclined at such an inclination angle δ. As shown in FIG. 4, in this embodiment, A groove bottom surface 19 of the chip discharge groove 13 connected to the rake surface 14 of the cutting blade 16 is formed so as to extend substantially linearly from the rake surface 14.
9 has a straight portion 20 in a cross section along the inclined plane P. Here, the straight portion 20 is formed by cutting the cutting edge 14 from the axis O of the tool body 11 in a cross section orthogonal to the axis O.
, That is, the end face radius R in the present embodiment, the groove bottom surface 19 in the cross section along the inclined plane P is within the range of the width W ₁ band of 0.1R, more preferably the width of 0.05R. are the portions fall within the band of W _2, in the present embodiment, the inner peripheral end of the rake face 14, the next cutting edge 16 adjacent to the tool rotation direction T side of the cutting edge 16 of the 1 Of the flank 15 and the bottom surface 19 of the groove, that is, to reach the heel portion 21,
The length L is set to 0.7 R or more with respect to the end mill radius R for any of the widths W ₁ and W ₂ .

[0020] Incidentally, as shown in FIG. 4, the rake face 14 in the present embodiment is formed in a concave curved surface, a positive radial rake angle r _r is given to the cutting edge 16. In FIG. 4, the symbol C indicates the axis O
Is a cross section along the inclined plane P of a cylindrical surface of the end mill radius R, that is, the rotation locus of the cutting edge 16 around the axis O. The radius in the short axis direction about the axis O is the end mill radius. R, the major axis is on the plane S, and one intersection with the major axis has an elliptical shape with one point Q on the cutting edge 16.

Thus, the endoscope thus constructed is
According to the drawing, the chip discharge connected to the rake face 14 of the cutting blade 16 is discharged.
On the groove bottom surface 19 of the groove 13, the outflow angle?
In the cross section along the inclined plane P extending in the
Width W to radius R ₁Is within the range of 0.1R
The linear portion 20 that fits is secured with a length L of 0.7R or more.
So that the chips can be smoothly removed along the linear portions 20.
Can be ejected, and chip resistance increases cutting resistance.
Prevents damage or damage to the finished surface of the workpiece
Thus, efficient cutting can be achieved. Also,
On the other hand, the sectional area and the second moment of area of the tool body 11
Is not impaired more than necessary,
Ensures tool rigidity while achieving good chip discharge performance
Excellent cutting that can secure and suppress vibration during cutting
Accuracy and stable tool life can be obtained.

Here, in the present embodiment, the inclined plane P
Is formed such that the width W ₁ is within a range of 0.1 R or less with respect to the end mill radius R and the length L is 0.7 R or more. , which is not longer a straight if the width W ₁ is large undulations enough above the 0.1 R, while there is a possibility that chip clogging occurs in a portion which is convex, the tool rigidity is impaired at a portion where the concave This is because there is a fear. Further, the length L of such a width W straight portion 20 be not fall ₁ ranges shorter below 0.7R, possibility is that it is impossible to reliably ensure good chip discharge performance .

[0023] Incidentally, the width W ₁ to define the linear portion 20 is desirably ideally 0, i.e. extend straight without straight portion 20 is bent even slightly on the inclined plane P It is desirable that the bends within 0.1R have an extremely small effect on the chip dischargeability and tool rigidity. However, the straight portion 20, since in this way it's is preferably a straighter, to be included with the width W ₂ within the range of 0.05R end mill radius R as described above is desirable. Also, regarding the length L, if only the chip discharging property is considered, ideally, the entire cross section of the chip discharging groove 13 along the inclined plane P is formed into a linear portion 20.
Although than is desirable that the actually or apply a predetermined radial rake angle r _r the rake face 14 connected to the cutting edge 16 is adjacent to the tool rotation direction T side of the cutting edge 16 cutting 1
Since a predetermined clearance angle has to be given to the flank 15 of 6, for example, in a four-flute end mill as in the present embodiment, the upper limit is about 1.5R.

By the way, especially in the four-flute end mill as in this embodiment, the cross section of the groove bottom surface 19 of the chip discharge groove 13 along the inclined plane P has a width W ₁ within 0.1R and a length L. Is provided with the linear portion 20 of 0.7R or more, the chip discharge groove 1 located on the rear side in the tool rotation direction T of the cutting edge 16 where the one point Q through which the inclined plane P passes is arranged.
As shown in FIG. 4, the groove bottom surface 19 of 3 has a convex curved surface bulging toward the outer peripheral side of the tool. However, since the chips generated by the cutting edge 16 at the point Q flow out along the inclined plane P, the chips are
The resistance acting on the tool body 11 by sliding on the rake face 14 connected to the rake face 14 also acts along the inclined plane P. On the other hand, in the present embodiment, the resistance
In the cross section along, the rake face 14 can secure a greater thickness on the rear side in the tool rotation direction T, and the linear portion 20 ensures tool rigidity. It is possible to more reliably prevent a situation in which vibration occurs in 11.

[0025]

As described above, according to the present invention,
In a cross section along an inclined plane extending in the direction of the chip discharge angle, a substantially linearly extending linear portion having a predetermined length or more is formed on the groove bottom surface of the chip discharge groove connected to the rake face of the cutting blade that generates the chip. By ensuring, it is possible to smoothly discharge chips without impairing the rigidity of the tool, and it is possible to promote efficient cutting while reliably preventing vibration of the tool body during cutting.

[Brief description of the drawings]

FIG. 1 is a side view showing an embodiment of the present invention.

FIG. 2 is a front view of the embodiment shown in FIG. 1 as viewed from a tool tip side.

FIG. 3 shows the embodiment shown in FIG.
The rake face 14 and the groove bottom face 19 of the chip discharge groove 13 and the inclined plane P passing through the point Q on the cutting edge 16.
FIG.

4 is a cross-sectional view of the tool main body 11 along the inclined plane P in the embodiment shown in FIG. 1 (a cross-sectional view taken along the line ZZ in FIG. 1).
It is.

FIG. 5 shows a conventional four-flute end mill, one cutting edge 4, a rake face 3 and a groove bottom surface 5 of a chip discharge groove 2 connected thereto, and an inclined plane P passing through a point Q on the cutting edge 4. FIG.

6 is a cross-sectional view of the tool main body 1 along an inclined plane P in the conventional example shown in FIG.

[Explanation of symbols]

Reference Signs List 11 tool body 13 chip discharge groove 14 rake face 15 flank 16 cutting edge 19 groove bottom of chip discharge groove 13 20 linear portion of groove bottom 19 O center axis of tool body 11 T tool rotation direction Q 1 on cutting edge 16 Point S Plane including point Q and axis O P Inclined plane R End mill radius W Width in the range of 0.1R for ₁ end mill radius R W ₂ Width in the range of 0.05R for end mill radius R L The length δ of the linear part 20 δ The inclination angle that the inclined plane P makes with respect to a plane perpendicular to the axis O

Claims (2)

[Claims] 1. A chip discharge groove is formed on an outer periphery of a substantially cylindrical tool body rotated around an axis, and an outer peripheral side of a groove wall surface which is a rake face facing the tool rotation direction side of the chip discharge groove. An end mill in which a cutting edge twisted around the axis is formed on a ridge, and the end mill passes through a point on the cutting edge, and
In a cross section along an inclined plane that is perpendicular to a plane including a point and the axis and is inclined at an inclination angle δ given by the following equation with respect to a plane perpendicular to the axis, the rake face of the cutting edge The groove bottom surface of the continuous chip discharge groove has a linear portion having a length of 0.7R or more in a portion sandwiched within a width of 0.1R or less with respect to an end mill radius R from the axis to the cutting edge. End mill. (Equation 1) 2. The method according to claim 1, wherein the linear portion has the end mill radius R.
2. The end mill according to claim 1, wherein a length of a portion included in a range of 0.05 R or less is 0.7 R or more. 3.