JP2011189463A - End mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent the occurrence of an unshaven part in a machinable material, by avoiding the fact that a cutting edge is not formed in an axial peripheral area of a distal end part, while improving the cutting quality by arranging bottom blades downward to a core. <P>SOLUTION: This end mill is provided by forming at least a pair of bottom blades 8 extending to the outer peripheral side from the axis O side in this distal end part in the distal end part of an end mill body 1 rotated around the axis O. Among this, a pair of bottom blades 8A have a positive radial directional rake angle in an outer peripheral side area more than a peripheral area A of the axis O, and are connected via a chisel part 10 when mutual distal end flanks 9 cross by extending toward the axis O side in the peripheral area A of the axis O. <P>COPYRIGHT: (C)2011,JPO&INPIT

Description

  The present invention relates to an end mill in which a bottom blade extending from the axis side to the outer peripheral side is formed at a tip end portion of an end mill body rotated around an axis.

  As an end mill having such a bottom blade, for example, Patent Document 1 discloses a ball end mill made of coated cemented carbide having a cutting edge whose rotation locus is substantially hemispherical. A chisel angle of 165 to 185 degrees, a chisel width of 0.01 to 0.1 mm, and a chisel blade length of 0.05 to 0.4 mm have been proposed. In this Patent Document 1, it is described that the chisel blade is made thinner and shorter to prevent the peeling phenomenon, and the bottom blade is arranged at a position that is as high as possible.

JP 2001-341026 A

  However, the bottom blade is arranged in a position that is as high as possible in this way, that is, the tangent line of the rake face at the bottom blade position in a cross section orthogonal to the rotation axis of the end mill is a straight line that passes through an axis parallel to the tangent line. On the other hand, when the bottom blade is arranged so as to be positioned on the end mill rotation direction side, the radial rake angle of the bottom blade becomes a negative angle, and the sharpness becomes dull, leading to an increase in cutting resistance.

  On the other hand, the bottom blade is so-called centered so that the tangent of the rake face at the position of the bottom blade in the cross section perpendicular to the axis is positioned on the rear side in the end mill rotation direction with respect to the straight line passing through the axis parallel to the tangent. Although the sharpness is improved by simply placing it at the bottom, the bottom edge of the end mill rotates in the area around the axis that is the center of rotation of the end mill, making it impossible to perform cutting. As a result, uncut material is left on the work material.

  The present invention has been made under such a background, and avoids the cutting edge from being formed in the peripheral region of the axis of the tip while improving the sharpness by arranging the bottom blade at the lower end. Thus, an object of the present invention is to provide an end mill that can prevent uncut parts from being left on the work material.

  In order to solve the above-described problems and achieve such an object, the present invention provides at least a pair of bottoms extending from the axis side to the outer peripheral side of the tip part at the tip part of the end mill body rotated about the axis. An end mill in which a blade is formed, and a pair of bottom blades have a positive radial rake angle in a region on the outer peripheral side of the peripheral region of the axis, and in a peripheral region of the axis, The tip flank surfaces of each other extend toward the axis and intersect with each other so as to be connected via a chisel portion.

  In the end mill configured in this way, the rake angle in the radial direction of the bottom blade is a positive angle in the region on the outer peripheral side of the region around the axis of the end portion of the end mill main body, so that a sharp sharpness can be ensured and the cutting can be performed. The resistance can be reduced. On the other hand, in the peripheral region of the axis that is the center of rotation of the end mill body tip, the tip flank surfaces of the pair of bottom blades extend to the axis and intersect to form a chisel portion. Since the bottom blade is connected via the portion, the cutting blade is not formed in the peripheral region of the axis, and it is possible to prevent the uncut material from being left on the work material.

  Here, in the chisel portion of the axial peripheral region where the tip flank surfaces of the bottom blades intersect with each other in this way, the axial rake angle is set to be larger on the negative angle side. In this axial peripheral region, the axial line As the rotational speed approaches zero, the rotation speed approaches 0, and the work piece is deformed so as to be crushed rather than scraped off with a cutting blade. Since the strength of the chisel portion is ensured by the negative angle, it is possible to avoid the end mill body from being damaged or deformed even in such a form, and promote smooth processing. be able to.

  The peripheral region of the axis line where the chisel portion is formed at the end portion of the end mill body is a circle having a diameter of 3% to 8% with respect to the outer diameter of the bottom blade centered on the axis line when viewed in the axial direction front end. It is desirable to be in the area. That is, if the peripheral area of the axis is smaller than the above range, and the range in which the chisel portion is formed is reduced accordingly, the strength of the chisel portion is reduced and a defect occurs during cutting, and in the central axis peripheral region. On the other hand, there is a possibility that the cutting edge may not exist. On the contrary, if the axial peripheral region becomes larger than the above range, the range of the chisel portion where the axial rake angle is set to the negative angle side as described above also becomes large. There is a risk of increasing the cutting resistance.

  In the present invention, a radius end mill in which a corner blade that is curved toward the rear end side in the axial direction is formed on the outer peripheral portion of the bottom blade in a convex curve shape toward the outer peripheral side. Although it is possible to apply to a square end mill formed so as to be substantially orthogonal to the outer peripheral blade formed on the outer peripheral portion of the end mill body at the outer peripheral portion, the bottom end as in the ball end mill described in Patent Document 1 is also possible. The blade is curved so as to be directed toward the rear end side in the axial direction as a whole by forming a convex curve shape such as a ¼ arc shape from the peripheral region of the axis at the tip of the end mill body toward the outer peripheral side, It is particularly effective when applied to a case where the chisel portion in the peripheral region of the axis at the tip of the end mill body is often involved in cutting.

  As described above, according to the present invention, in the region around the axis line of the end portion of the end mill main body, the work material is secured while ensuring sufficient cutting edge strength by the chisel portion that intersects the tip flank of the bottom blade. On the other hand, in the region on the outer circumference side of the peripheral region of the axis, the cutting resistance is reduced by increasing the rake angle in the radial direction of the bottom blade to a positive angle. Can be encouraged.

It is a side view which shows 1st Embodiment at the time of applying this invention to a ball end mill. It is an enlarged front view of the axial direction front end view of embodiment shown in FIG. It is a side view which shows 2nd Embodiment at the time of applying this invention to a radius end mill. It is an enlarged front view of the axial direction front end view of the embodiment shown in FIG.

  1 and 2 show a first embodiment when the present invention is applied to a ball end mill. In the present embodiment, the end mill body 1 is formed of a hard material such as cemented carbide in a generally cylindrical shape with the axis O as the center, and the rear end side portion (the right side portion in FIG. 1) remains a cylindrical shank. The tip side portion (the left side portion in FIG. 1) is a cutting blade portion 3, and the shank portion 2 is gripped by the spindle of the machine tool and rotated in the end mill rotation direction T around the axis O. On the other hand, the workpiece is cut by the cutting edge portion 3 by being fed relatively to the workpiece in the direction intersecting the axis O.

  Here, the cutting blade portion 3 has chip discharge grooves 4 that twist toward the rear side in the end mill rotation direction T from the front end portion toward the rear end side in the axis O direction. A plurality of strips (four strips in the present embodiment) are formed at intervals, and the outer peripheral edge of the wall surface of the outer peripheral portion of the cutting blade portion 3 facing the end mill rotation direction T side of the chip discharge groove 4 is an axis line. The outer peripheral blade 5 is formed so that the rotation locus around O forms a single cylindrical surface centered on the axis O. Accordingly, the wall surface facing the end mill rotation direction T side of the chip discharge groove 4 is a rake face of the outer peripheral blade 5. In addition, the outer diameter of the portion from the portion where the chip discharge groove 4 is cut to the outer peripheral side to the front end of the shank portion 2 on the rear end side of the cutting blade portion 3 is the outer diameter of the shank portion 2 or the rotation trajectory of the outer peripheral blade 5. The neck 6 is slightly smaller than the outer diameter of the cylinder (hereinafter referred to as the cutting edge outer diameter D).

  On the other hand, a gash 7 is formed at the tip of the cutting edge 3 so that the tip of the chip discharge groove 4 is further cut out toward the inner peripheral side. At the outer peripheral edge of the facing wall surface, a bottom blade 8 is formed extending from the rotation axis side to the outer peripheral side of the end mill main body 1 tip, that is, from the rotation center side at the end mill main body 1 front end. Therefore, the wall surface facing the end mill rotation direction T of the gash 7 is the rake face of the bottom blade 8.

  However, in the end mill of this embodiment, which is a ball end mill, the rotation trajectory of the bottom blade 8 around the axis O is smoothly connected to the cylinder having the center on the axis O and the rotation trajectory of the outer peripheral blade 5. A single semi-convex spherical shape having a diameter equal to the outer diameter D of the cutting edge is formed, and therefore each bottom blade 8 has a convex curve shape of approximately ¼ arc as viewed from the direction facing the wall surface of the gash 7. become. Further, these bottom blades 8 draw a convex curve that is convex toward the end mill rotation direction T as shown in FIG. 2 when viewed from the front in the direction of the axis O, and go from the rotation center side to the outer peripheral side at the end portion of the end mill body 1. Accordingly, it extends toward the rear side in the end mill rotation direction T.

  These bottom blades 8 are formed so as to be lowered in the outer peripheral side of the peripheral region A of the axis O at the tip end portion of the end mill body 1, that is, in the peripheral region of the region near the rotation center. That is, in the region on the outer peripheral side from the peripheral area A of the axis O, the tangent of the rake face (the wall facing the end mill rotation direction T of the gasche 7) in the cross section perpendicular to the axis O is the tangent. It is arranged to be located rearward in the end mill rotation direction T from a straight line that intersects the axis O in parallel, that is, the axis of the bottom blade 8 and the axis as the rake face moves from the bottom blade 8 toward the inner peripheral side in the same section. The rake angle in the radial direction of the bottom blade 8 is a positive angle so as to be directed rearward in the end mill rotation direction T with respect to a straight line connecting O. Alternatively, the distance from the axis O to the tip flank 9 when the gash 7A enters (the position of the boundary between the peripheral area A of the axis O and the area on the outer periphery thereof) when viewed from the front in the direction of the axis O is determined by end mill rotation. When the direction T side is positive, the end mill rotation direction T rear side is negative, and twice that is referred to as the gash core thickness, the gash core thickness is negative, and the region on the outer peripheral side from the entry position of the gash 7A The rake angle in the radial direction of the bottom blade 8 is positive.

  Here, as for the gasches 7 formed at the respective tips of the four chip discharge grooves 4, every other pair of gashes 7A in the circumferential direction extends closer to the axis O than the other pair of gashes 7B. Is formed. However, the pair of gashs 7A do not cross each other, and the distal end of the pair of bottom blades 8A formed on the outer peripheral edge of the pair of gashs 7A is in the peripheral region A of the axis O at the distal end of the cutting blade part 3. A chisel portion 10 is formed such that the flank 9 extends to the axis O side and intersects.

  More specifically, the chisel portion 10 is configured so that the pair of bottom blades 8A approach each other from the outer peripheral side region B toward the inner peripheral side while the pair of bottom blades 8A are in the center-down state in the front end view of the axis O direction. It extends to the vicinity, but does not cross over the axis O, and in this embodiment, it is bent at an obtuse angle before the axis O, and is bent to the end mill rotation direction T side. Accordingly, the axis O is intersected by the tip flank 9 of the pair of bottom blades 8A thus cut off, and the intersecting ridge line between the tip flank 9 intersects the axis O to form the chisel blade 11. Will form.

  On the other hand, each of the pair of gashes 7A and each of the other pair of gashes 7B located on the side of the end mill rotation direction T are formed so as to cross each other, thereby forming an outer peripheral edge of the other pair of gashes 7B. The other pair of formed bottom blades 8B are formed to extend to the outer peripheral side with a positive radial rake angle from a position on the outer peripheral side than the pair of bottom blades 8A. Here, the peripheral area A of the axis O of the end portion of the end mill body 1 where the chisel portion 10 is formed is 3% to 8% with respect to the cutting edge outer diameter D in the end view in the direction of the axis O in this embodiment. It is an area within a circle of diameter.

  In the end mill (ball end mill) of the present embodiment configured as described above, the bottom blade 8 is centered downward in the region on the outer peripheral side from the peripheral region A of the axis O at the tip of the end mill body 1 and the radial rake angle thereof. Is set at a regular angle, the sharpness of the bottom blade 8 can be improved. For this reason, the cutting resistance at the time of cutting can be reduced and the finish surface accuracy can be improved.

  On the other hand, if the bottom blade 8 is simply lowered, the inner peripheral ends of the bottom blade 8 cross each other in the peripheral area A of the axis O at the end of the end mill body 1, and the bottom of the axis O is in the peripheral area A. In contrast, in the end mill configured as described above, the end flank 9 of the pair of bottom blades 8A extends toward the axis O and intersects in the peripheral region A of the axis O. Accordingly, the chisel portions 10 are connected to each other, and in this chisel portion 10, it is possible to perform cutting by causing the intersecting ridge line formed by the tip flank surfaces 9 to intersect with each other as the chisel blade 11.

  Therefore, according to the end mill having the above-described configuration, it is possible to prevent uncut parts from being generated in the work material due to the occurrence of the portion where the bottom blade 8 does not exist in the peripheral area A of the axis O in this way. Further improvement can be achieved. In addition, the chisel blade 11 is in the peripheral area A of the axis O, and the rotational speed at the time of cutting is close to 0, so that the cutting form is crushed rather than scraping off the work material. Since the chisel blade 11 itself is an intersecting ridge line where the tip flank surfaces 9 of the pair of bottom blades 8A cross each other, the axial rake angle is set to be larger on the negative angle side, thereby ensuring high strength. Therefore, in spite of the cutting form as described above, it is possible to prevent the chisel portion 10 from being damaged or deformed and to promote smooth and stable cutting.

  By the way, if the range of the axis O peripheral region A at the tip end portion of the end mill main body 1 where the chisel portion 10 is formed is too small, the strength of the chisel portion 10 is reduced to cause defects during cutting, and the end mill main body 1 tip end. There is a possibility that the cutting edge does not exist in the peripheral area A of the axis O of the part. On the other hand, if the peripheral area A of the axis O is too large, the chisel portion 10 having a negative rake angle in the axial direction may become large and cutting resistance may not be reduced. The peripheral area A of the axis O where the axis 10 is formed is a circle having a diameter of 3% to 8% with respect to the outer diameter of the bottom blade 8 centered on the axis O in the front view of the axis O direction, that is, the cutting edge outer diameter D It is desirable to be in the area.

  In the first embodiment, the case where the present invention is applied to a ball end mill in which the bottom blade 8 has a convex curve shape such as a substantially ¼ arc is described. In such a ball end mill, Since the chisel blade 11 is often involved in cutting, it is particularly effective when the present invention is applied.

  However, in addition to such a ball end mill, the present invention can be applied to a square end mill in which the bottom blade 8 extends along a plane perpendicular to the axis O and is substantially perpendicular to the outer peripheral blade 5, or such a bottom end. The present invention can also be applied to a radius end mill in which a convex curved corner blade is formed at a corner portion where the blade 8 and the outer peripheral blade 5 intersect. FIG. 3 and FIG. 4 show a second embodiment when the present invention is applied to a radius end mill as described above, and the elements common to the first embodiment are described with the same reference numerals. Is omitted.

  That is, in the radius end mill of the second embodiment, the bottom blade 8 formed at the tip end portion of the end mill main body 1 in the cutting blade portion 3 has the axis O from the axis O side toward the outer periphery as shown in FIG. A substantially straight middle bottom blade 8a extending along a plane perpendicular to the outer surface or extending toward the tip side slightly toward the outer peripheral side, and an outer peripheral portion of the bottom blade 8 Convex curve shape such as approximately ¼ arc as viewed from the end mill rotation direction T side, which curves toward the rear end side in the axis O direction as it contacts the inner bottom blade 8a and continues toward the rear end side in the axis O direction. And a corner blade 8b.

  Furthermore, the bottom blade 8 is such that the middle bottom blade 8a can be given a positive rake angle in the radial direction on the outer peripheral side of the peripheral region A of the axis O as shown in FIG. The corner blade 8b extends toward the rear side in the end mill rotation direction T as it goes toward the outer peripheral side. However, the rake face of the corner blade 8b extends along the axis O. The tangent at the position of the corner blade 8b in the cross section perpendicular to the cross section is set to be located on the rear side in the end mill rotation direction T with respect to the straight line parallel to the tangent line and intersecting the axis O. That is, in the same cross section, the rake face is the corner. As it goes from the blade 8b to the inner peripheral side, it is made to go to the rear side in the end mill rotation direction T with respect to the straight line connecting the corner blade 8b and the axis O, and its radial rake angle is a positive angle. It has been made as to.

  Also in this embodiment, the four bottom blades 8 are configured such that the pair of bottom blades 8A extend to the vicinity of the axis O rather than the other pair of bottom blades 8B. A chisel portion 10 having a chisel blade 11 is formed in the peripheral area A of the axis O by the surfaces 9 intersecting each other. However, in the present embodiment, the pair of bottom blades 8A is directed from the inner peripheral end toward the axis O side so as to draw a concave curve as shown in FIG. It is cut out.

  Also in the radius end mill of the second embodiment configured as described above, the bottom blade 8 has a positive diameter in a region on the outer peripheral side of the peripheral region A of the axis O of the end portion of the end mill main body 1 as in the first embodiment. Since the rake angle is arranged so as to give a direction rake angle, it is possible to improve the sharpness and reduce the cutting resistance. Further, since the chisel portion 10 is formed in the peripheral area A of the axis O at the tip end portion of the end mill body 1 to connect the pair of bottom blades 8A, for example, the end mill main body 1 is fed obliquely toward the tip end side with respect to the axis O. Even in the case of cutting, it is possible to ensure the strength in the peripheral region A of the axis O and prevent the occurrence of defects or the like.

  In the first and second embodiments, the chip discharge grooves 4 are formed at equal intervals in the circumferential direction, and accordingly, the bottom blade 8 and the outer peripheral blade 5 are also arranged at equal intervals in the circumferential direction. However, for example, the pair of bottom blades 8A and the other pair of side blades 8B are 180 ° rotationally symmetric with respect to the axis O, respectively, and the distance between the bottom blade 8A and the bottom blade 8B adjacent to the end mill in the rotational direction T side. The bottom blades 8 and the outer peripheral blades 5 connected to the bottom blades 8B and the bottom blades 8B adjacent to the same side blades 8A and the bottom blades 8B adjacent to the rear side in the end mill rotation direction T are different in the circumferential direction. You may arrange | position so that it may become. Further, there may be two or more pairs of other bottom blades 8B.

DESCRIPTION OF SYMBOLS 1 End mill main body 3 Cutting blade part 4 Chip discharge groove 5 Outer peripheral blade 8 Bottom blade 8A A pair of bottom blades 8B Another pair of bottom blades 9 Tip flank 10 Chisel portion 11 Chisel blade O Axis line of end mill main body T End mill rotation direction A Area around the axis O at the end of the end mill body 1

Claims (3)

  An end mill in which at least a pair of bottom blades extending from the axial line side to the outer peripheral side at the distal end portion is formed at a distal end portion of an end mill body rotated around an axis, and the pair of bottom blades is The outer peripheral region has a positive rake angle in the radial direction than the peripheral region, and in the peripheral region of the axis line, the tip flank surfaces extend toward the axis side to cross the chisel portion. An end mill characterized by being connected to each other.   The peripheral region of the axis is a region within a circle having a diameter of 3% to 8% with respect to the outer diameter of the bottom blade centered on the axis in the axial front end view. End mill as described in   The said bottom blade is curving so that it may become a convex curve shape and goes to the said axial direction rear end side as it goes to the outer peripheral side from the peripheral region of the said axis line in the front-end | tip part of the said end mill main body. Or the end mill of Claim 2.

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