JP2007136627A - End mill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To smoothly discharge chips, in an unequal twist end mill or an unequal flute spacing end mill, while securing reditity and strength. <P>SOLUTION: In this end mill, the cutting edges 5 are formed on the outer peripheral side ridges of wall surfaces 4A pointing at the end mill rotating direction T of a plurality of chip discharge grooves 4 formed in the outer periphery of the tip of the end mill body 1 rotated round the axis O, at least one cutting edge 5A of the cutting edges 5 is largely different in circumferential space from the adjacent cutting edge 5B on the rotating direction T side of the end mill from the other cutting edges 5B at least partially along the direction of the axis O, and in the above one cutting edge 5A, a chip discharge groove 4 formed on the outer peripheral side ridge of a wall surface 4B is such that the diameter DA of the web thickness circle CA round the axis O contacting the groove base 4C is different from the diameter DB of the web thickness circle CB of the chip discharge groove 4 where the other cutting edges 5B are formed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to an end mill in which a plurality of chip discharge grooves are formed on the outer periphery of a tip end portion of an end mill body rotated about an axis, and a cutting edge is formed on a peripheral edge portion of a wall surface facing the end mill rotation direction. It is.

  In this type of end mill, as described in, for example, Patent Documents 1 to 3, a plurality of cutting blades that are twisted in a spiral shape are formed on the outer periphery of the tip end portion of the end mill body, and at least one of these cutting blades. By making the torsion angle of the cutting blade an unequal torsion different from the torsion angle of the other cutting blades, the circumferential distance of the cutting blades was made different at least in part along the axial direction of the end mill body. What is called an unequal twist end mill or an unequal lead end mill has been proposed. That is, in the end mills described in Patent Documents 1 and 3, the cutting edges are equally spaced in the circumferential direction at the front end of the end mill body, and the circumferential distance is different on the rear end side than this. In the end mill described in Literature 2, the end mill body rear end of the cutting edge is equally spaced in the circumferential direction, and the circumferential distance is different on the tip side than this.

Therefore, in such a non-uniformly twisted end mill, in the part where the circumferential interval of the cutting edge is different, the interval at which each cutting edge bites the work material is different, and the twist angle is also different. It is possible to prevent the end mill body from generating periodic vibrations that resonate with its natural frequency, resulting in chatter vibrations caused by such resonances. Can be prevented. In addition, even with an unequal division end mill in which only the circumferential interval of the cutting edge is unequal while keeping the same twist angle, the cutting edge biting interval becomes an unequal period, so that the same effect can be obtained. it can.
JP-A 63-89212 JP-A-63-89213 JP-A 63-89214

  By the way, in the end mill in which the circumferential intervals between the cutting blades are different in this way, the intervals at which the cutting blades bite into the work material as described above are different. The cutting amount in the feed direction also differs for each cutting blade, and the cutting amount by the cutting blade, that is, the amount of generated chips and the thickness of the chips also differ. That is, in one cutting blade in which the circumferential interval between the cutting blades adjacent to the end mill rotation direction side is larger than the other cutting blades, the cutting blade on the end mill rotation direction side cuts the work material. Since the end mill main body is fed more before the one cutting edge bites into the work material, chips having a larger wall thickness than other cutting edges are generated and the amount of generated chips increases.

  However, in this way, in the cutting blade whose distance from the cutting blade adjacent to the end mill rotation direction side is increased, the width of the chip discharge groove located in the end mill rotation direction of the cutting blade is widened, so that a certain amount of chip discharging performance is achieved. Although it is possible to ensure, depending on cutting conditions and the like, it becomes difficult to securely accommodate the chips that are generated with a large thickness as described above, which are not easily curled, in the chip discharge grooves and to discharge them smoothly. There is a fear. On the other hand, on the other hand, in the cutting blade in which the circumferential interval between the cutting blade adjacent to the end mill rotation direction side is smaller than that of other cutting blades, the amount of generated chips is less than necessary. The chip discharge groove is deepened and the end mill body is greatly cut out, and the rigidity and strength of the cutting blade and the end mill body itself are impaired. There is a risk that it will not be demonstrated.

  The present invention has been made under such a background, such as the above-mentioned non-uniformly twisted end mill and the non-uniformly divided end mill. In an end mill whose circumferential spacing is different from that of other cutting edges, it is possible to discharge chips smoothly for cutting edges whose spacing is larger than other cutting edges. The purpose of the present invention is to provide an end mill that can sufficiently secure the rigidity and strength of a cutting blade that is smaller than the cutting edge of the end mill and that can sufficiently secure the rigidity and strength of the end mill body itself.

  In order to solve the above-described problems and achieve such an object, the present invention provides a plurality of chip discharge grooves formed on the outer periphery of a tip end portion of an end mill body rotated around an axis, and the end mills of these chip discharge grooves A cutting edge is formed on the outer peripheral side ridge portion of the wall surface facing the rotation direction, and at least one of the cutting edges is at least partially along the axial direction on the end mill rotation direction side. An end mill in which a circumferential interval between adjacent cutting edges has a size different from that of other cutting edges, wherein the at least one cutting edge has the chip discharge groove formed on the outer peripheral side ridge portion of the wall surface. The diameter of the core thick circle centering on the axis contacting the groove bottom surface is different from the diameter of the core thick circle of the chip discharge groove on which the other cutting blade is formed. .

  In the end mill configured as described above, for at least one cutting edge whose distance from the cutting edge adjacent to the end mill rotation direction side is different from that of the other cutting edge, the wall surface in which the cutting edge faces the end mill rotation direction The chip discharge groove formed on the outer peripheral side ridge is not only the groove width, but also the diameter of the core thick circle that touches the groove bottom surface, that is, the core thickness, is the center of the chip discharge groove on which other cutting blades are formed. Since the size is different from the thickness of the thick circle, it is possible to reliably ensure the chip dischargeability required according to the width of the gap and the rigidity and strength of the cutting blade or the end mill body.

  For example, in the case where the at least one cutting edge has a circumferential interval larger than that of the other cutting edge with respect to the cutting edge adjacent to the end mill rotation direction side, the at least one cutting edge is formed. By making the diameter of the core thick circle in contact with the bottom surface of the chip discharge groove formed smaller than the diameter of the core thick circle of the chip discharge groove on which the other cutting blades are formed, as described above. Even if at least one cutting blade generates a large amount of thick and difficult-to-curl chips, the depth of the chip discharge groove can be increased to facilitate smooth discharge.

  On the contrary, in the case where the at least one cutting edge has a circumferential interval smaller than the other cutting edges with respect to the cutting edge adjacent to the end mill rotation direction side, The diameter of the core thick circle in contact with the groove bottom surface of the chip discharge groove on which at least one cutting edge is formed is larger than the diameter of the core thick circle of the chip discharge groove on which the other cutting blade is formed. As a result, it is possible to improve the rigidity and strength of the cutting blade by preventing the end mill body from being cut out by the deep chip discharge groove while ensuring a sufficient groove depth in the chip discharge groove for a small amount of chip generation. Can do.

  Note that these configurations can be simultaneously adopted for one end mill. That is, as described above, when at least one of the plurality of cutting blades has a circumferential interval larger than the other cutting blades with the cutting blade adjacent to the end mill rotation direction side. The other cutting blade has a smaller circumferential interval with respect to the above-mentioned circumferentially increased cutting blade, so that the core thickness circle diameter of the chip discharge groove is increased. Thus, while ensuring the rigidity of the other cutting blade, smooth chip discharging performance can be obtained by reducing the core thickness circle diameter of the chip discharging groove in the at least one cutting blade.

  On the other hand, in order to ensure such smooth chip discharging performance and cutting blade rigidity according to the width of the circumferential interval between the plurality of cutting blades, in addition to the above configuration, the chip discharge groove has a rear end in the end mill rotation direction. With respect to the flank face connected to the cutting edge formed on the wall surface facing the flank, the flank face connected to the at least one cutting edge whose distance from the cutting edge separated from and contacting the end mill rotation direction is different from that of the other cutting edge. It is desirable that the shape of the cross section perpendicular to the axis is different from the flank face connected to the other cutting blade.

  That is, when the at least one cutting edge has a circumferential interval larger than that of the other cutting edge adjacent to the cutting edge adjacent to the end mill rotation direction side, as described above, As the cutting amount increases, a large cutting load acts on the cutting edge. On the other hand, the flank surface connected to the at least one cutting edge is bent and bent in the cross section. If it is formed so as to go to the inner peripheral side of the end mill body as it goes to the rear side in the end mill rotation direction, it is possible to secure a larger thickness of the end mill body on the rear side in the end mill rotation direction of the cutting blade. It is possible to prevent the occurrence of defects or the like by giving the cutting blade sufficient rigidity and strength against the load.

  In addition, when the flank of at least one cutting edge having the above-described interval is formed in a convexly curved cross section, the cutting edge adjacent to the rear side in the end mill rotation direction of the at least one cutting edge is: The other cutting blade is desirable. That is, the other cutting edge is made smaller in distance to the at least one cutting edge adjacent to the end mill rotating direction side, and accordingly, the amount of generated chips is reduced. Even if the flank of at least one cutting edge adjacent to the end mill rotation direction side of the blade is formed in a convex bend and the cross-sectional area of the chip discharge groove of the other cutting edge is reduced, chip discharge is hindered. It is not carried out, and smooth machinability can be maintained.

  Similarly, in the case where the at least one cutting edge has a circumferential interval larger than the other cutting edges with respect to the cutting edge adjacent to the end mill rotation direction side, this at least one cutting edge is used. By forming a recess recessed on the inner peripheral side of the end mill body while being concavely bent in the cross section on the flank face connected to the cutting blade adjacent to the end mill rotation direction side of the cutting blade, the gap is large and thick. It is possible to secure a larger cross-sectional area of the chip discharge groove of the at least one cutting edge where a large amount of large chips are generated, thereby facilitating smoother chip discharge.

  In addition, when forming a recess in this way, the cutting blade adjacent to the end mill rotation direction side of the at least one cutting blade in which the recess is formed on the flank is used as the other cutting blade. desirable. That is, in this other cutting blade, the amount of generated chips is reduced as described above, and accordingly, the cutting load on the other cutting blade is also reduced. Even if it forms, sufficient rigidity and intensity | strength according to cutting load can be ensured.

  1 to 3 show a first embodiment of the present invention. In this embodiment, the end mill main body 1 is formed of a hard material such as cemented carbide and has a substantially cylindrical shape centering on the axis O, and the rear end side portion (the right side portion in FIG. 1) remains a cylindrical shank. The end portion (left side portion in FIG. 1) is a cutting edge portion 3 and the shank portion 2 is held by the main shaft of the machine tool and rotated in the end mill rotation direction T around the axis O while the axis 2 By being sent out in a direction crossing O, the cutting edge portion 3 cuts the work material.

  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. A cutting blade (outer peripheral blade) 5 is formed on each of the peripheral edge portions of the wall surface 4A facing the end mill rotation direction T side of the chip discharge grooves 4. Accordingly, the wall surface 4A is the rake face of the cutting blade 5, and the wall surface 4B facing the end mill rotation direction T rear side of the chip discharge groove 4 extending from the cutting blade 5 to the rear side in the end mill rotation direction T is the cutting blade 5. In this embodiment, the four cutting edges 5 are formed as a rake face, and the wall surface 4A is formed as the rake face. It is formed so as to be twisted spirally in accordance with the twist of the chip discharge groove 4.

  On the other hand, a gash 6 extending from the chip discharge groove 4 to the inner peripheral side is formed at the tip of the end mill body 1, and the cutting edge is provided at the tip side edge of the gash 6 and the wall surface 4A. A bottom blade 7 extending from the tip of 5 to the vicinity of the axis O of the inner periphery of the end mill body 1 is formed. Here, the end mill of the present embodiment is a square end mill in which the bottom blade 7 and the cutting blade 5 that is an outer peripheral blade are substantially orthogonal to each other along a rotation locus around the axis O. Note that the cutting blades 5 that are outer peripheral blades are configured so that the rotation trajectories around the respective axis lines O coincide with each other to form a cylindrical surface with the axis line O as the center.

  Further, in the present embodiment, the wall surface 4B of the chip discharge groove 4 used as the flank of the cutting blade 5 is configured so that the cross section perpendicular to the axis O has substantially the same shape in any of the chip discharge grooves 4. Yes. That is, these wall surfaces 4B gradually move toward the inner peripheral side of the end mill body 1 while drawing a convex curve as it goes from the cutting edge 4 toward the rear side in the end mill rotation direction T in the cross section, and then, the wall surface 4B is steeper than this. The chip is formed so as to recede to the inner peripheral side of the end mill main body 1 in a substantially straight line, and then toward the inner peripheral side of the end mill main body 1 while drawing a convex curve more gently than this steep slope. The groove 4 is formed so as to reach the groove bottom surface 4C. Therefore, the wall surface 4B is bent concavely in the cross section by the substantially linear portion and the convex curved portion on the rear side in the end mill rotation direction T. On the other hand, a recess 4D that is recessed toward the inner peripheral side of the end mill body 1 is formed.

  Further, in the cross section, the groove bottom surface 4C has a concave curve shape that smoothly touches the convex curve portion that forms the concave portion 4D, and is smoothly connected to the wall surface 4A that is a rake face as it is. The wall surface 4A is substantially linear in the vicinity of the cutting edge 5, and extends slightly toward the end mill rotation direction T side toward the outer peripheral side of the end mill body 1 so that a positive rake angle is given to the cutting edge 5. ing.

  Further, the plurality of cutting blades 5 are at least one of the cutting blades 5 at least partially along the axis O direction in the circumferential direction with the cutting blade 5 adjacent to the end mill rotation direction T side. Is different in size from the other cutting blades 5. And the chip discharge groove | channel 4 in which this at least 1 cutting blade 5 which made the space | interval of the circumferential direction different in this way was formed in the outer peripheral side ridge part of the said wall surface 4A makes the axis line O which contact | connects the said groove bottom face 4C. The diameter of the core thick circle at the center, that is, the core thickness, is also different from the diameter of the core thick circle in which the other cutting edge 5 is in contact with the groove bottom surface 4 of the chip discharge groove 4 formed on the wall surface 4A.

  Here, in this embodiment, it is set as the structure of the unequal division | segmentation end mill by which the twist angle with respect to the axis line O of the cutting blades 5 was made mutually equal, and the space | interval of the circumferential direction was varied. Therefore, in the present embodiment, at least one cutting edge 5 extends over the entire length in the axis O direction at the cutting edge portion 3, and the circumferential interval between the cutting edges 5 adjacent to the end mill rotation direction T side is different from that of the other cutting edges 5. That is, the cutting edges 3 extend in the direction of the axis O while being twisted according to the torsion angle while maintaining the cross-sectional shape orthogonal to the axis O shown in FIG. Accordingly, the bottom blade 7 connected to the at least one cutting blade 5 also has a circumferential interval between the bottom blade 7 adjacent to the end mill rotation direction T side as shown in FIG. 7 and a different size.

  More specifically, the four cutting blades 5 in the present embodiment include the first cutting blade 5A having a larger circumferential interval with the one adjacent to the end mill rotation direction T side, and the circumference of the first cutting blade 5A. The second cutting blades 5B whose direction intervals are reduced are formed so as to be 180 ° rotationally symmetric with respect to the axis O alternately with each other. Accordingly, the first cutting blade 5A is at least one cutting blade in the invention according to claim 2 of the present application, and is another cutting blade in the invention according to claim 3, and conversely the second cutting blade. 5B is another cutting blade in the invention according to claim 2 of the present application, and 5B is at least one cutting blade in the invention according to claim 3.

  Of these, the chip discharge groove 4 in which the first cutting edge 5A is formed on the wall surface 4A has its center thick circle CA inscribed in the groove bottom surface 4C with the axis O as the center, and the second cutting edge 5B has the wall surface. The core thickness circle CB inscribed in the groove bottom surface 4C of the chip discharge groove 4 formed in 4A is made slightly smaller, that is, the diameter DA of the core thickness circle CA is smaller than the diameter DB of the core thickness circle CB. It is made smaller. Here, in the present embodiment, the sandwiching angle between the first cutting edge 5A and the second cutting edge 5B adjacent to the end mill rotation direction T side between the axis O is 100 °, and the second cutting edge 5B Whereas the included angle between the axis O with the first cutting edge 5A adjacent to the end mill rotation direction T side is 80 °, the diameter DA of the core thick circle CA is the outer diameter of the cutting edge 5 D, that is, 0.6 × D with respect to the diameter of the cylinder formed by the cutting edge 5 around the axis O, and the diameter DB of the core thick circle CB is 0.7 × D with respect to the outer diameter D of the cutting edge 5. It is said that.

  Therefore, in the end mill configured as described above, the circumferential distance between the cutting edge 5 adjacent to the end mill rotation direction T side is different from that of the other cutting edges 5 with respect to at least one cutting edge 5. The chip discharge groove 4 that receives and discharges the chips generated by the at least one cutting edge 5 is also different from the chip discharge grooves 4 of the other cutting edges 5 in the diameter of the core thickness circle that contacts the groove bottom surface 4C. Because of its size, it is possible to reliably ensure the dischargeability required for the chip discharge groove 4 and the rigidity, strength, etc. required for the cutting blade 5 or the end mill body 1 itself according to the width of the gap. It becomes.

  That is, in the present embodiment, the distance from the second cutting blade 5B adjacent to the end mill rotation direction T side is larger than that of the second cutting blade (the other cutting blade in the invention according to claim 2 of the present application) 5B. For the first cutting blade 5A that is enlarged (at least one cutting blade in the invention according to claim 2 of the present application) 5A, the diameter DA of the core thickness circle CA in the chip discharge groove 4 is the chip of the second cutting blade 5B. Combined with the fact that the discharge groove 4 is smaller than the diameter DB of the core thick circle CB, the groove depth is increased, and the gap is increased to increase the groove width. A large cross-sectional area extending in the circumferential direction and radial direction of the end mill body 1 can be secured in the chip discharge groove 4 of the cutting blade 5A. For this reason, the cutting amount in the feed direction increases with the increase in the interval, and thus the thick and difficult-to-curl chips generated in large quantities by the first cutting blade 5A can be quickly generated without causing clogging. Therefore, it can be accommodated in the chip discharge groove 4 and discharged smoothly.

  On the other hand, with respect to the second cutting edge (at least one cutting edge in the invention according to claim 3 of the present application) 5B, the distance from the first cutting edge 5A adjacent to the end mill rotation direction T side is the second cutting edge. The first cutting blades other than the cutting blade 5B (other cutting blades in the invention according to claim 3 of the present application) other than the cutting blades 5A are made to be smaller than the first cutting blades 5A. Only a small amount of thin-walled chips are generated as compared with the cutting blade 5A.

  And with respect to such a second cutting edge 5B, the diameter DB of the core thickness circle CB of the chip discharge groove 4 is increased, that is, the part where the end mill body 1 is cut away by reducing the groove depth. Since the protrusion amount in the radial direction from the groove bottom surface 4C to the second cutting edge 5B is kept small, a sufficient cross-sectional area for the above-described chips is provided in the chip discharge groove 4. While ensuring, it becomes possible to improve the rigidity and strength of the second cutting edge 5B, that is, the rigidity and strength of the end mill body 1. Therefore, by combining the cutting blades 5A and 5B with unequal division in the circumferential direction to prevent periodic vibration from acting, chatter vibration is generated in the end mill body 1 during cutting. It can be surely prevented, and smooth and accurate cutting can be promoted.

  In addition, in the present embodiment, the first cutting edge 5A having a larger interval from the second cutting edge 5B adjacent to the end mill rotation direction T side, and the first cutting edge adjacent to the end mill rotation direction T side conversely. The second cutting blades 5B having a small distance from the blade 5A are alternately arranged in the circumferential direction of the end mill body 1 in the cutting blade portion 3, and therefore at least one cutting blade in the invention according to claim 2 is provided. A second cutting blade 5B as at least one cutting blade in the invention according to claim 3 is adjacent to the first cutting blade 5A as a blade on the rear side in the end mill rotation direction T, and the second cutting blade. The diameter DB of the core thick circle CB of the chip discharging groove 4 formed on the wall surface 4A is made larger than the diameter DA of the core thick circle CA.

  For this reason, with respect to the first cutting edge 5A in which the interval is increased and the cutting amount in the feed direction is large, and therefore the cutting load is large, the depth of the chip discharge groove 4 connected to the rear of the end mill rotation direction T is shallow. That is, on the rear side in the end mill rotation direction T of the first cutting edge 5A, it is possible to secure a larger wall thickness on the outer peripheral side of the end mill body 1, so that the rigidity of the first cutting edge 5A itself can be increased. The strength can be further improved, and chatter vibration can be prevented more reliably.

  Furthermore, in the present embodiment, the wall surface 4B of the chip discharge groove 4 that is connected to the rear side in the end mill rotation direction T of each of the first and second cutting blades 5A and 5B and serves as a flank surface of these cutting blades 5, As described above, the concave portion 4 </ b> D that is recessed on the inner peripheral side of the end mill body 1 while being concavely bent in the cross section orthogonal to the axis O is formed. For this reason, especially about the 1st cutting blade 5A in which the space | interval with the 2nd cutting blade 5B adjacent to the end mill rotation direction T side was enlarged, the cross-sectional area of the chip discharge groove | channel 4 in which the chip | tip is accommodated and discharged | emitted. Can be ensured even larger, and more reliable chip discharge can be promoted to achieve smooth cutting. On the other hand, since the load acting at the time of cutting is small in the second cutting edge 5B in which the cutting amount in the feed direction is small, even if such a recess 4D is formed on the wall surface 4B serving as a flank, the cutting load is increased. On the other hand, sufficient rigidity and strength can be maintained.

  Next, FIG. 4 and FIG. 5 are cross-sectional views orthogonal to the axis O of the cutting edge portion 3 showing the second embodiment of the present invention, and the same reference numerals are used for elements common to the first embodiment. The explanation is omitted. That is, in the said 1st Embodiment, the wall surface 4B made into the flank which continues to the end mill rotation direction T back side of the said chip discharge groove 4 and continues to the cutting blade 5 in the end mill rotation direction T side of this cutting blade 5 Whereas the cross-sectional shapes are substantially the same regardless of the spacing between the adjacent cutting edges 5, in this second embodiment, the end mill rotates at least partially along the axis O direction of the cutting edge portion 3. With respect to the at least one cutting blade 5 having a circumferential interval different from that of the other cutting blades 5 with respect to the cutting blade 5 adjacent to the direction T, the flank face is connected to the at least one cutting blade 5. The shape of the cross section perpendicular to the axis O of the wall surface 4B is also different from the wall surface 4B which is connected to the other cutting blade 5 and serves as the flank surface.

  More specifically, in the second embodiment, the arrangement of the first and second cutting blades 5A and 5B and the interval in the circumferential direction, and the first and second cutting blades 5A and 5B are arranged on the outer peripheral side. The shape and position of the wall surface A and the groove bottom surface 4C of the chip discharge groove 4 formed on the ridge, and the core thickness circles CA and CB and their diameters DA and DB in contact with the groove bottom surface 4C of each chip discharge groove 4 are the first. It is the same as that of the embodiment. In addition, the wall surface 4B facing the end mill rotation direction T rear side of the chip discharge groove 4 connected to the cutting edge 5 and serving as a flank thereof is also a first cutting edge adjacent to the end mill rotation direction T side (claims of the present application). For the second cutting blade (the other cutting blade in the invention according to claims 5 to 8 of the present application) 5B having a small interval with 5A, at least one cutting blade in the invention according to 5-8, the first Similar to the embodiment, the shape is provided with a recess 4 </ b> D that is recessed on the inner peripheral side of the end mill body 1 while being bent and bent in a cross section orthogonal to the axis O.

  However, with respect to the first cutting edge 5A in which the circumferential interval between the second cutting edge 5B adjacent to the end mill rotation direction T side is increased, the end mill rotation direction T used as the flank face is provided. Unlike the cross-sectional shape of the wall surface 4B, which is the relief surface of the second cutting edge 5B having the recess 4D as described above, the wall surface 4B connected to the rear side is a cross section orthogonal to the axis O as shown in FIG. Are formed so as to be directed toward the inner peripheral side of the end mill body 1 as it goes toward the rear side in the end mill rotation direction T while being convexly bent.

  Here, in the present embodiment, the wall surface 4B, which is the flank of the first cutting edge 5A, has a second cross section in the cross section perpendicular to the axis O from the cutting edge 5A toward the rear side in the end mill rotation direction T. Draw a convex curve similar to the wall surface 4B used as the flank of the cutting edge 5B, gently move toward the inner periphery of the end mill body 1, and then slightly steeper than this, but still draw a convex curve while the end mill body 1 is formed so as to extend toward the inner peripheral side and smoothly come into contact with the concave curve formed by the groove bottom surface 4C of the chip discharge groove 4. That is, the wall surface 4B is a portion that is concavely bent toward the inner peripheral side of the end mill main body 1 such as the recess 4D before reaching the groove bottom surface 4C of the chip discharge groove 4 toward the rear side in the end mill rotation direction T. Is not formed.

  In the end mill according to the second embodiment configured as described above, in addition to the effect obtained by making the diameters DA and DB of the core thickness circles CA and CB different from each other in the same manner as in the first embodiment, the above-described distance is large. Since the first cutting blade 5A and the small second cutting blade 5B have different cross-sectional shapes of the wall surface 4B which is the flank of the cutting blade 5 adjacent in the end mill rotation direction T, this interval Therefore, the chip discharge performance, rigidity, and strength required by the wide and narrow width can be more accurately imparted to the chip discharge groove 4, the cutting edge 5, or the end mill body 1. That is, for the first cutting edge 5A that generates a large amount of chips with a large interval, the wall surface 4B that is the flank of the second cutting edge 5B adjacent to the end mill rotation direction T side has a first wall 5B. Since the recess 4D is formed in the same manner as in the first embodiment, it is possible to ensure a large cross-sectional area of the chip discharge groove 4 that accommodates a large amount of chips by the first cutting blade 5A and to improve chip discharge performance. Can do.

  And on the other hand, about the wall surface 4B used as the flank of this 1st cutting blade 5A itself, the cross section is made into the shape which goes to an inner peripheral side as it goes to the end mill rotation direction T back side while convexly bending. Therefore, the end mill main body 1 has the end mill rotation direction T rear side with respect to the first cutting edge 5A which generates a large amount of thick chips because the gap is large and the cutting amount in the feeding direction is large. A large wall thickness (back metal) can be secured. That is, as a large amount of thick chips are produced in this way, it becomes possible to give higher rigidity and strength to the first cutting edge 5A itself on which a larger cutting load acts. Therefore, according to the end mill of the second embodiment, chatter vibration can be prevented more reliably and effectively, and the first cutting edge 5A may be damaged due to such a large cutting load. Can prevent the end mill life.

  Moreover, since the first and second cutting edges 5A and 5B are alternately arranged in the circumferential direction also in this embodiment, the wall surface 4B used as the flank of the first cutting edge 5A that is bent in this way. Is the wall surface 4B facing the end mill rotation direction T rear side of the chip discharge groove 4 of the second cutting edge 5B adjacent to the rear side of the end mill rotation direction T. Secondly, in the cutting blade 5B, the interval is reduced. Since the amount of generated chips is small, even if the cross-sectional area of the chip discharge groove 4 of the second cutting edge 5B is somewhat reduced due to such convex bending of the wall surface 4B, the chip discharge performance is hindered. There is nothing. Further, in the second cutting edge 5B, since the amount of chips generated is small and the load acting at the time of cutting is small, even if the recess 4D is formed on the wall surface 4B which is the flank, such cutting load Can maintain sufficient rigidity and strength.

  In the first and second embodiments, the torsion angles of the cutting blades 5 with respect to the axis O are made equal, and the circumferential interval is different from the other cutting blades by at least one cutting blade. Although the case where the present invention is applied to the unequal division end mill has been described, the twist angle of at least one of the plurality of cutting blades 5 is different from the other cutting blades as shown in FIGS. 6 and 7. Therefore, the present invention is applied to an unequal twist end mill or an unequal lead end mill in which the distance between the at least one cutting edge and the cutting edge adjacent to the end mill in the rotational direction is different from that of other cutting edges. Is also possible. FIG. 6 shows that the cross-sectional shape of the wall surface 4B, which is the flank face of each cutting blade 5, is made substantially the same as in the first embodiment, and FIG. 7 is the same as that in the second embodiment. Similarly, the cross-sectional shape of the wall surface 4B is made different, and the same reference numerals are assigned to portions common to the first and second embodiments, respectively.

  Here, in the end mills shown in FIGS. 6 and 7, the four cutting blades 5 are rotated by 180 ° on the outer periphery of the end portion (cutting blade portion 3) of the end mill main body 1 as in the first and second embodiments. The cutting blades 5 are formed symmetrically, and the cutting blades 5 are arranged at equal intervals in the circumferential direction at the tip thereof, and the pair of cutting blades 5 that are arranged rotationally symmetrical among them are the first cutting blades 5A. Thus, the twist angle α is set to be larger than the twist angle β of the other pair of cutting blades 5 as the second cutting blade 5B. Therefore, the circumferential interval between the first cutting edge 5A and the second cutting edge 5B adjacent to the end mill rotation direction T side gradually increases toward the rear end side in the axis O direction, and conversely the second The circumferential interval between the cutting edge 5B and the first cutting edge 5A adjacent to the end mill rotation direction T side gradually decreases toward the rear end side in the axis O direction. For example, FIG. 6 and FIG. In the ZZ cross-section, the cross-sectional shapes shown in FIGS. 3 and 5 are exhibited.

  In the end mills shown in FIGS. 6 and 7, the cutting blades 5 are arranged at equal intervals in the circumferential direction at the tip as described above, and thus the bottom blades 7 are also arranged at equal intervals in the circumferential direction. The cutting edges 5 are formed so as to be equally spaced in the circumferential direction at the rear end or at any position between the front end and the rear end, or not at any position including the front and rear ends. In other words, it is only necessary that the cutting edges 5 be at unequal intervals at least in part along the axis O direction. In addition, when the cutting blades 5 are arranged at equal intervals in the circumferential direction at any position between the front end, the rear end, or the front and rear ends as described above, the diameter of the core thickness circle is at these positions. Or the cross-sectional shape of the wall surface 4B of the chip discharge groove 4 may be made equal.

  Further, with regard to the at least one cutting blade 5 that is different from the other cutting blades 5 in the interval between the adjacent cutting blades 5 on the end mill rotation direction T side, the rake angle and clearance angle are also different from each other. An angle different from 5 may be used. Moreover, although the said 1st, 2nd embodiment and FIG. 6 demonstrated the square end mill in which the said cutting blade 5 used as an outer peripheral blade and the bottom blade 7 are substantially orthogonal in a rotation locus, the rotation locus | trajectory of a bottom blade is a hemisphere. It is also possible to apply the present invention to a ball end mill formed into a shape, or a radius end mill in which a bottom blade and an outer peripheral blade (cutting blade 5) are connected via a corner blade having a substantially 1/4 arc shape.

It is a side view which shows 1st Embodiment at the time of applying this invention to an unequal division | segmentation end mill. It is the front view which looked at the embodiment shown in Drawing 1 from the axis line O direction tip side. It is ZZ sectional drawing in FIG. It is a side view which shows the 2nd Embodiment of this invention. It is ZZ sectional drawing in FIG. It is a side view which shows the case where the 1st Embodiment of this invention is applied to an unequal twist end mill. It is a side view which shows the case where the 2nd Embodiment of this invention is applied to an unequal twist end mill.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 End mill main body 3 Cutting edge part 4 Chip discharge groove 4A Wall face (rake face) which faces the end mill rotation direction T side of the chip discharge groove 4
4B Wall surface (flank) facing the rear side T in the end mill rotation direction T of the chip discharge groove 4
4C Chip bottom surface of chip discharge groove 4 4D Concavity 5 Cutting blade 5A First cutting blade 5B Second cutting blade 7 Bottom blade O End mill body 1 axis T Rotation direction of end mill body 1 during cutting CA, CB Center thick circle DA, DB Diameter of core thick circle CA, CB

Claims (8)

  A plurality of chip discharge grooves are formed on the outer periphery of the end portion of the end mill body rotated about the axis, and cutting edges are formed on the outer peripheral side ridge portions of the wall surfaces of the chip discharge grooves facing the end mill rotation direction. At least one of the cutting blades of at least one of the cutting blades has a circumferential interval between the cutting blade adjacent to the end mill rotation direction and a size different from that of the other cutting blades, at least in part along the axial direction. The chip discharge groove, in which the at least one cutting edge is formed on the outer peripheral side ridge of the wall surface, has a diameter of a core thickness circle centered on the axis line in contact with the groove bottom surface. An end mill characterized in that it has a size different from the diameter of the core thick circle of the chip discharge groove in which the cutting blade is formed.   The at least one cutting edge has a circumferential interval with a cutting edge adjacent to the end mill rotation direction side larger than other cutting edges, and the chip discharge groove in which the at least one cutting edge is formed. 2. The end mill according to claim 1, wherein a diameter of the core thick circle in contact with the groove bottom surface is smaller than a diameter of the core thick circle of the chip discharge groove on which the other cutting blade is formed.   The at least one cutting edge has a circumferential interval with a cutting edge adjacent to the end mill rotation direction side smaller than other cutting edges, and the chip discharge groove in which the at least one cutting edge is formed. 2. The end mill according to claim 1, wherein a diameter of the core thick circle in contact with the groove bottom surface is larger than a diameter of the core thick circle of the chip discharge groove on which the other cutting blade is formed.   On the wall surface facing the rear side in the end mill rotation direction of the chip discharge groove, a flank surface connected to the cutting blade is formed, and the flank surface connected to the at least one cutting blade has a cross-sectional shape orthogonal to the axis. The end mill according to any one of claims 1 to 3, wherein the end mill has a shape different from a flank face connected to the other cutting edge.   The at least one cutting edge has a circumferential interval between the cutting edge adjacent to the end mill rotation direction side larger than the other cutting edges, and the flank face connected to the at least one cutting edge is 5. The end mill according to claim 4, wherein the end mill is formed so as to be directed toward the inner peripheral side of the end mill main body as it goes toward the rear side in the end mill rotation direction while being bent in a cross section.   The end mill according to claim 5, wherein a cutting blade adjacent to the rear side in the end mill rotation direction of the at least one cutting blade is the other cutting blade.   The at least one cutting edge has a circumferential interval between the at least one cutting edge and the cutting edge adjacent to the end mill rotation direction side larger than the other cutting edges, and the at least one cutting edge is adjacent to the end mill rotation direction side. 7. The recess according to any one of claims 4 to 6, wherein a concave portion is formed on the inner peripheral side of the end mill body while being concavely bent in the cross section. End mill. The end mill according to claim 7, wherein a cutting blade adjacent to the end mill rotating direction side of the at least one cutting blade is the other cutting blade.

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