JP2010201565A - End mill - Google Patents

Abstract

[PROBLEMS] To improve the accuracy and quality of a machined surface cut by a bottom blade when cutting an end mill main body longitudinally, and forming it at a position away from the center of rotation of the end mill main body tip. Provided is an end mill capable of preventing the bottom blade from being damaged and extending the end mill life.
A plurality of bottom blades 9 extending from the outer peripheral side to the inner peripheral side are formed at intervals in the circumferential direction at the tip of an end mill body 1 rotated about an axis O. At least one bottom blade 9A extends to the vicinity of the axis O toward the inner peripheral side at the end of the end mill body 1, while the other bottom blade 9B is spaced from the axis O toward the inner peripheral side. The end mill body 1 is inclined to the rear end side of the end mill body 1 at an inclination angle larger than that of the bottom blade 9A as it goes to the inner peripheral side.
[Selection] Figure 2

Description

  In the present invention, the end mill body is rotated about its axis, and sent in a direction perpendicular to the axis to perform cutting. The present invention relates to an end mill capable of forming holes and the like.

  As described above, as an end mill capable of feeding the end mill main body to the tip end side in the axial direction, that is, longitudinally feeding, for example, in Patent Document 1, at least one bottom blade among a plurality of bottom blades is: The end mill extends from the vicinity of the center of rotation at the tip of the end mill to the outer peripheral side and has a 0 ° or negative radial rake angle, and the other bottom blade extends from the position away from the center of rotation to the outer peripheral side. Further, there is disclosed one formed so as to have a larger rake angle in the radial direction on the positive angle side than the at least one bottom blade.

  In such an end mill, a large pushing force acts when the end mill main body is longitudinally fed, and at least one bottom blade that cuts the work material portion facing the vicinity of the tool rotation center is set to 0 ° or negative. By giving a rake angle in the radial direction, a high cutting edge strength can be provided, and it is possible to prevent the cutting edge from being damaged against an excessive cutting load acting on the cutting of the work material part.

Japanese Utility Model Publication No. 6-66910

  By the way, in the end mill described in Patent Document 1, the work material portion facing the vicinity of the rotation center at the end of the end mill main body at the time of vertical feeding is the at least one bottom blade extending to the vicinity of the rotation center as described above. On the other hand, the work material part facing the outer peripheral side of the end mill body tip is cut by all the bottom blades formed at the end mill body tip of this at least one bottom blade and the other bottom blade. It will be.

  However, if the bottom blades involved in cutting differ between the work material part facing the vicinity of the center of rotation at the tip of the end mill body and the work material part facing the outer peripheral side, depending on the feed amount of vertical feed, There may be a step at the boundary of the material part, which may impair the accuracy and quality of the processed surface. On the other hand, since the inner peripheral edge separated from the rotation center of the other bottom blade is the closest to the rotation center among the other bottom blades, the pushing force at the time of vertical feeding is also increased, and a defect or the like There is also a problem that is likely to occur.

  The present invention has been made under such a background, and when the end mill main body is vertically fed and cut as described above, the accuracy and quality of the work surface cut by the bottom blade is improved. An object of the present invention is to provide an end mill that can extend the life of the end mill by preventing damage to the bottom blade formed at a position away from the center of rotation of the end mill main body.

  In order to solve the above-described problems and achieve such an object, the present invention is configured such that a plurality of bottom blades extending from the outer peripheral side to the inner peripheral side are spaced in the circumferential direction at the tip of the end mill body rotated about the axis. And at least one bottom blade of the bottom blades extends toward the inner periphery at the tip of the end mill body, while the other bottom blades It extends to a position spaced apart from the axis toward the peripheral side, and inclines toward the rear end side of the end mill body at a larger inclination angle than the at least one bottom blade as it goes toward the inner peripheral side. It is characterized by being.

  In the end mill configured in this way, with respect to at least one bottom blade extending to the vicinity of the axis at the tip of the end mill body, that is, to the rotation center, another bottom blade extending to a position spaced apart from the axis is provided on the inner peripheral side. Since it is inclined toward the rear end side of the end mill main body with a large inclination angle as it goes, when the end mill main body is longitudinally fed, only the at least one bottom blade extending mainly to the vicinity of the axis is involved in the cutting. For this reason, it is possible to prevent other bottom blades from being involved depending on the cutting site of the work material, and to prevent a step from being generated on the processed surface by the bottom blades.

  In addition, since the other bottom blade is not involved in the cutting in this way, a pressing force does not act on the other bottom blade during vertical feeding, and damage such as a chipping can be prevented. In particular, since the other bottom blades are inclined toward the rear end side toward the inner peripheral side at a larger inclination angle than the at least one bottom blade, the retreat amount with respect to the at least one bottom blade is on the inner peripheral side. Since it gradually increases and becomes maximum at the inner peripheral end, it is possible to reliably prevent damage at the inner peripheral end of the other bottom blade.

  Further, the other bottom blade is inclined to the rear end side of the end mill body toward the inner peripheral side at a larger inclination angle than the outer peripheral side at the inner peripheral side of the end of the end mill main body, thereby longitudinally feeding. In this case, it is possible to more reliably prevent the inner peripheral end of the other bottom blade from participating in the cutting. Moreover, the tip pocket can be secured by forming a space around the portion extending to the vicinity of the axis of the at least one bottom blade by inclining the inner peripheral side of the other bottom blade to be larger than the outer peripheral side. As a result, it is possible to prevent chips generated by such a portion from becoming clogged and causing an increase in cutting resistance and a deterioration in machined surface accuracy.

  If the difference in the inclination angle between the at least one bottom blade and the other bottom blade is too small, the inner peripheral side of the other bottom blade may be involved in the cutting depending on the feed amount of the vertical feed. In the case of a square end mill, for example, in the case of a square end mill, the crossing angle with the outer peripheral blade becomes smaller at the outer peripheral end of other bottom blades, and defects are likely to occur. There is a fear. For this reason, it is desirable that the difference in the inclination angle on the outer peripheral side of the end mill main body between these at least one bottom blade and the other bottom blade is in the range of 2 to 5 °.

  As described above, according to the present invention, when cutting is performed by longitudinally feeding the end mill body, only at least one bottom blade extending to the vicinity of the axis of the end mill body tip among the bottom blades is mainly involved in the cutting. In this way, it is possible to improve the accuracy and quality of the processed surface by the bottom blade, and prevent the other bottom blades from being damaged particularly at the inner peripheral end, thereby providing an end mill having a long life.

It is a side view which shows the 1st Embodiment of this invention. It is the enlarged front view which looked at the embodiment shown in Drawing 1 from the axis O direction tip side. FIG. 3 is a cross-sectional view taken along AA in FIG. 2 (a cross section taken along a first bottom blade 9A). FIG. 3 is a BB cross section (cross section along a second bottom blade 9B) in FIG. 2. It is the enlarged front view which looked at the 2nd Embodiment of this invention from the axial direction front end side. FIG. 6 is a cross-sectional view taken along the line BB in FIG. 5 (a cross section taken along the second bottom blade 9B).

  In the first embodiment of the present invention shown in FIGS. 1 to 4, the end mill body 1 is formed of a hard material such as cemented carbide and has a substantially cylindrical shape centering on the axis O, and a rear end side portion ( The right side portion in FIG. 1 is a cylindrical shank portion 2 and the tip side portion (left side portion in FIG. 1) is a cutting blade portion 3, and the shank portion 2 is held on the spindle of the machine tool and is axial. By being sent out to the work material while being rotated in the end mill rotation direction T around O, the work material is cut by the cutting blade portion 3.

  On the outer periphery of the cutting edge portion 3, a plurality (four in this embodiment) of chip discharge grooves 4 that are twisted toward the rear side in the end mill rotation direction T around the axis O from the front end to the rear end side are formed. The wall surfaces of the chip discharge grooves 4 facing the end mill rotation direction T have a concave curve shape recessed in the rear side of the end mill rotation direction T in the cross section perpendicular to the axis O, Each of the outer peripheral blades 5 is formed. Therefore, the wall surface is a rake face of the outer peripheral blade 5, that is, the outer peripheral blade rake face 6. In this embodiment, the four outer peripheral blades 5 are twisted to the chip discharge groove 4 in which the outer peripheral blade rake face 6 is formed. They are formed so as to be twisted together.

  On the other hand, a gash 7 extending inward from the chip discharge groove 4 is formed at the tip of the end mill body 1, and the wall surface of the gash 7 facing the end mill rotation direction T has a concave curved cross section. The front end side portion of the outer peripheral edge rake face 6 is formed to be cut out in a flat shape. Then, a bottom blade 9 extending from the tip of the outer peripheral blade 5 to the inner peripheral side of the end mill body 1 at the tip side ridge portion of the wall surface, that is, the intersecting ridge line portion of the wall surface and the tip flank 8 of the end mill body 1 tip. Is formed.

  Therefore, in this embodiment, the wall surface of the gash 6 is the scooping surface of the bottom blade 9, that is, the bottom blade scooping surface 10, and a plurality of (four strips) bottom blades 9 are provided as shown in FIG. When viewed from the front end side in the axis O direction, the end mill body 1 is formed so as to extend linearly from the outer peripheral end to the inner peripheral side. In the end mill of the present embodiment, the rotation trajectory of the outer peripheral blade 5 around the axis O is substantially cylindrical with the axis O as the center, and the outer peripheral blade 5 and the bottom blade 9 are angled with the same rotation trajectory. It is a square end mill that intersects with

  Here, as shown in FIG. 2, the plurality of bottom blades 9 are two first bottom blades (upper and lower in FIG. 2) extending from the outer peripheral end intersecting the outer peripheral blade 5 to the vicinity of the axis O at the end of the end mill body 1. A bottom blade extending in the direction (at least one bottom blade in the present invention) 9A and 2 extending from the outer peripheral end toward the inner peripheral side up to a position spaced apart from the upper axis O relative to the first bottom blade 9A. Second bottom blades (bottom blades extending in the left-right direction in FIG. 2, other bottom blades in the present invention) 9 </ b> B are alternately arranged in the circumferential direction.

  However, the first bottom blade 9A is not intersected with the axis O at the end of the end mill body 1, and the inner peripheral end thereof is positioned with a slight gap between the axis O and A chisel portion 11 is formed between the inner peripheral ends of the first bottom blade 9A. The chisel portion 11 is formed by intersecting the tip flank surfaces 8 of the first bottom blade 9A. Crossed with O. Further, in the present embodiment, the first and second bottom blades 9A and 9B are formed at equal intervals in the circumferential direction. Therefore, the end mill body 1 is formed to be 180 ° rotationally symmetric about the axis O.

  Furthermore, in the present embodiment, the bottom edge rake face 10 of the first bottom blade 9A is formed in such a manner that the positions of the inner peripheral ends of the first and second bottom blades 9A and 9B are different. The gash 7 is extended beyond the tip flank 8 connected to the second bottom blade 9B to the side opposite to the side where the first bottom blade 9A extends in the radial direction with respect to the axis O, thus The extended gash 7 of the first bottom blade 9A and the gash 7 of the second bottom blade 9B adjacent to the end mill rotation direction T side are communicated with each other on the inner peripheral side of the end mill body 1 tip. .

  Each of the bottom blades 9 has an inclination angle (a watermark angle or a medium low angle) with respect to a plane perpendicular to the axis O so as to go to the rear end side of the end mill body 1 from the outer peripheral end toward the inner peripheral side. Among them, the inclination angle β given to the second bottom blade 9B shown in FIG. 4 is made larger than the inclination angle α given to the first bottom blade 9A shown in FIG. Yes. Here, it is desirable that the difference β−α between these inclination angles is in the range of 2 to 5 °. In this embodiment, α = 2 °, β = 5 °, and β−α = 3 °. ing.

  Accordingly, when the end mill body 1 is also fed to the front end side in the direction of the axis O to form an inclined groove or concave hole in the work material by such an end mill, the bottom blade 9 is involved in cutting. What is mainly performed is the first bottom blade 9A having a small inclination angle α. And this 1st bottom blade 9A is extended from the outer periphery end which cross | intersects the outer periphery blade 5 to the axial line O vicinity of the end mill main body 1, and cuts the process part of the workpiece material by this bottom blade 9 uniformly. Therefore, according to the end mill having the above-described configuration, it is possible to avoid the formation of a step or the like on the processing surface by the bottom blade 9, and to improve the processing surface accuracy and processing surface quality during vertical feeding. Can be planned.

  On the other hand, the second bottom blade 9B is inclined toward the rear end side of the end mill body 1 at a larger inclination angle β than the first bottom blade 9A as it goes from the outer peripheral end toward the inner peripheral side. Thus, the first base blade 9A is retracted most greatly in the direction of the axis O. Accordingly, the inner peripheral end of the second bottom blade 9B is hardly involved in cutting, and therefore, the pushing force during the cutting load and vertical feed does not act. It is possible to prevent the inner peripheral end from being damaged, such as a defect, thereby extending the end mill life.

  In the first embodiment, the second bottom blade 9B is also inclined so as to go to the rear end side of the end mill body 1 as it goes straight toward the inner peripheral side, like the first bottom blade 9A. In order to more reliably prevent the damage at the inner peripheral end of the second bottom blade 9B as described above, the second bottom as in the second embodiment of the present invention shown in FIGS. It is desirable that the blade 9B is formed in a polygonal line shape so as to incline toward the rear end side of the end mill body 1 at a larger inclination angle γ on the inner peripheral side of the end mill body 1 tip than on the outer peripheral side. In the second embodiment, the same reference numerals are assigned to portions common to the first embodiment.

  Here, in the second embodiment, in the first embodiment, the portion on the inner peripheral side of the tip flank 8 connected to the second bottom blade 9B is larger than the outer peripheral portion as it goes toward the inner peripheral side. The second bottom blade 9B, which is the intersecting ridge line portion between the tip flank 8 and the bottom blade rake face 10, is formed into a polygonal line as described above by cutting out into an inclined flat surface at an inclination angle γ. In addition, since the cross section along 9 A of 1st bottom blades of the end mill main body 1 is the same as that of 1st Embodiment shown in FIG. 3, illustration is abbreviate | omitted.

  Therefore, in such an end mill of the second embodiment, the inner peripheral end of the second bottom blade 9B can be disposed at a position further retracted toward the rear end side of the end mill body 1 than in the first embodiment. Therefore, it is possible to reliably avoid the occurrence of a cutting load or a pushing force on the inner peripheral end and prevent the occurrence of damage more effectively.

  Moreover, when the inner peripheral side of the second bottom blade 9B is retracted at a larger inclination angle γ in this way, the end mill rotation direction T of the first bottom blade 9A adjacent to the rear side in the end mill rotation direction T is The larger space is formed by expanding the gasche 7. Therefore, since the space formed in this way can secure a large chip pocket of the first bottom blade 9A mainly involved in cutting during vertical feeding, according to the second embodiment, the first Chips generated by the bottom blade 9A can be accommodated in the chip pocket and discharged smoothly, and the clogging of such chips increases the cutting resistance or damages the work surface and impairs its quality and accuracy. It is possible to prevent this from happening.

  In these first and second embodiments, the difference in the inclination angle β at the outer peripheral portion of the second bottom blade 9B with respect to the inclination angle α of the first bottom blade 9A is 2 to 5 ° as described above. It is desirable to be within the range. If the difference α−β between the inclination angles α and β is too small, the second bottom blade 9B is also involved in the cutting when the feed amount in the longitudinal feed is large, and the above-mentioned effects are reliably achieved. If the difference α−β between the inclination angles α and β is too large, especially when the present invention is applied to the square end mill as in the first and second embodiments. The crossing angle with the outer peripheral blade 5 becomes small at the outer peripheral end of the second bottom blade 9B, and a defect or the like is likely to occur at the outer peripheral end.

  In addition to being applied to the square end mill as described above, the present invention is applied to a radius end mill in which a corner R blade having a convex arc shape is formed between the outer peripheral edge of the bottom blade 9 and the outer peripheral blade 5, for example. It is also possible. In the present embodiment, the first and second bottom blades 9A and 9B are arranged so as to be alternately and equally spaced in the circumferential direction as shown in FIG. The groove width of the end mill body 1 is made different by changing the groove width of the first bottom blade 9A and the second bottom blade 9B, or by changing the twist angle of the chip discharge groove 4. The distance between the blades 9 is different from the first bottom blade 9A to the second bottom blade 9B toward the rear side in the end mill rotation direction T, and from the second bottom blade 9B to the first bottom blade 9A. You may do it.

DESCRIPTION OF SYMBOLS 1 End mill main body 3 Cutting blade part 4 Chip discharge groove 5 Outer peripheral blade 6 Outer peripheral blade scoop surface 7 Gash 8 Tip flank 9 Bottom blade 9A First bottom blade (at least one bottom blade)
9B Second bottom blade (other bottom blade)
10 Bottom edge rake face O Axis line of end mill body 1 End mill rotation direction α Inclination angle of first bottom blade 9A β Inclination angle of second bottom blade 9B γ Inclination angle of inner peripheral side portion of second bottom blade 9B

Claims (3)

  A plurality of bottom blades extending from the outer peripheral side toward the inner peripheral side are formed at intervals in the circumferential direction at the tip of the end mill body rotated about the axis, and at least one of the bottom blades is While extending to the vicinity of the axis toward the inner peripheral side at the tip of the end mill body, the other bottom blade extends toward the inner peripheral side to a position spaced from the axis, An end mill characterized in that it is inclined toward the rear end side of the end mill body at an inclination angle larger than that of the at least one bottom blade as it goes toward the inner peripheral side.   The other bottom blade is inclined toward the rear end side of the end mill main body toward the inner peripheral side at a larger angle than the outer peripheral side on the inner peripheral side of the tip end of the end mill main body. Item 1. The end mill according to Item 1.   The difference in the inclination angle between the at least one bottom blade and the other bottom blade on the outer peripheral side of the tip end of the end mill body is in the range of 2 to 5 °. The end mill according to 2.

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