JP2012200836A - End mill with coolant hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an end mill with a coolant hole enabling the efficient cooling of a bottom edge and the rake face thereof and also enabling the injection direction of a coolant to be maintained even when the bottom edge is re-ground or re-polished.SOLUTION: A chip discharge flute 4 and an outer peripheral edge 5 which are twisted around the axis O of an end mill body 1 are formed on the top end outer periphery of the end mill body rotated about the axis O. A gash 6 and a bottom edge 7 are formed at the top end of the chip discharge flute 4. A coolant hole 8 twisted in the direction opposite to the outer peripheral edge 5 is formed in the end mill so as to extend from the gash 6 toward the rear end of the end mill body 1. A lead Lh (mm) of the coolant hole 8 has the relation of following formula 1 with respect to a lead Lp (mm) of the outer peripheral edge 5, a radius R (mm) of the bottom edge 7, a number Z of edges of the bottom edge 7, and an integer N of one or more.

Description

  The present invention relates to an end mill with a coolant hole in which a plurality of outer peripheral blades that are spirally twisted are formed on the outer periphery of a tip end portion of an end mill body, and a plurality of spirally twisted coolant holes are also formed in the end mill body. It is.

  As such an end mill with a coolant hole, for example, Patent Document 1 discloses a work material by providing an opening for supplying cutting oil to a blade bottom of the end mill, that is, a groove bottom (gash) on the rake face side of the bottom blade. There has been proposed a technique in which cutting oil is directly sprayed onto a rake face that becomes the highest temperature due to friction with chips and chips to efficiently cool the rake face. Furthermore, this Patent Document 1 also describes that the direction of ejection from the opening is made closer to the cutting point by making the lead of the cutting oil supply path different from the lead of the outer peripheral blade.

JP-A-8-318419

  On the other hand, in Patent Document 1, when the bottom blade is reground when the lead of the cutting oil supply path is different from the lead of the outer peripheral blade as described above, the bottom blade after regrinding is performed. In contrast, it is described that the position of the opening of the supply path is shifted, and the effect of suppressing tool wear by efficient cooling may be reduced. However, Patent Document 1 does not suggest any means for solving such a problem.

  The present invention has been made under such a background, and it is possible to achieve efficient cooling by injecting coolant toward the bottom blade and its rake face, as well as re-grinding the bottom blade, An object of the present invention is to provide an end mill with a coolant hole capable of maintaining such a coolant injection direction even when re-polished.

  In order to solve the above problems and achieve such an object, according to the present invention, a chip discharge groove that twists around the axis is formed on the outer periphery of the tip of the end mill body that rotates around the axis. A gash is formed on the front end side of the discharge groove, and a bottom blade is formed on the front edge of the wall surface facing the rotation direction of the end mill, and a rear end side of the end mill body from the outer peripheral end of the bottom blade. An outer peripheral blade that is twisted with a constant lead Lp (mm) is formed around the axis, while the outer edge is opposite from the outer peripheral blade around the axis toward the rear end side of the end mill body. A coolant hole that is twisted with a constant lead Lh (mm) is formed so as to extend into the core thickness circle of the end mill body, and the lead Lh (mm) of this coolant hole is the lead L of the outer peripheral blade. (Mm), a radius R (mm) from the axis to the outer peripheral edge of the bottom blade, the number Z of blades of the bottom blade, and an integer N of 1 or more, It is characterized by.

  In the end mill with the coolant hole configured as described above, the coolant hole is opposite to the outer peripheral blade with the coolant hole toward the rear end side with respect to the outer peripheral blade that twists from the outer peripheral end of the bottom blade toward the rear end side of the end mill body. Since it is formed so as to be twisted in the direction and opened in the gash, the coolant hole in the vicinity of the opening in the gash of the bottom blade faces the wall surface facing the end mill rotation direction of the gash that becomes the bottom blade and its rake face. It will extend as you do.

  Therefore, as in the case where the direction of twisting of the coolant hole and the outer peripheral blade described in Patent Document 1 is the same and the lead is made different, the coolant is injected along the rake face of the bottom blade. The coolant can be directly sprayed toward the bottom blade and its rake face, so that efficient cooling and lubrication can be achieved.

  Further, in the end mill with the coolant hole having the above-described configuration, the lead Lh (mm) of the coolant hole has a lead Lp (mm) of the outer peripheral blade and a radius R (mm) from the axis to the outer peripheral end of the bottom blade. And the number of blades Z of the bottom blade and an integer N equal to or greater than 1, the relationship of the above formula 1 is established. For example, a revolving path of the bottom blade forms during re-polishing like a ball end mill. When the end mill body tip is polished and retracted by the hemisphere, that is, the radius R (mm), and the gash and the bottom blade are re-formed on the tip side of the outer peripheral blade, the coolant hole opening is the integer N Accordingly, a gash formed by regrinding in a chip discharge groove continuous with the gasche that has been opened before regrinding or a gash different from this is opened.

  For example, a plurality of chip discharge grooves are formed on the outer periphery of the end portion of the end mill body at equal intervals in the circumferential direction, and a constant lead Lh (mm) is provided to all the plurality of gashes formed on the tip side of the plurality of chip discharge grooves. When the outer peripheral blades connected to the bottom blades at the tips of these gashes are all formed at regular intervals in the circumferential direction with a constant lead Lp (mm), the integer N = 1, if the end mill body tip is retracted by regrinding by radius R (mm), the coolant hole after regrind rotates the endmill of the chip discharge groove connected to the gasche that was opened before regrinding Openings are made in the gasches formed on the tip side of the chip discharge groove adjacent in the direction.

  Therefore, according to the end mill having the above-described configuration, the coolant hole can always be opened in the gash of the bottom blade in the direction facing the bottom blade and the rake face as described above, even if re-polishing is performed in this way. Further, efficient cooling and lubricity are not impaired by re-polishing, and a high tool wear suppression effect, welding prevention effect, and cutting resistance reduction effect can be achieved over a long period of time.

  Furthermore, the lead Lp (mm) of the outer peripheral blade is a radius R (mm) from the axis to the outer peripheral end of the bottom blade, the number of blades Z of the bottom blade, and the integer N of 1 or more. When the relationship of the following formula 2 is satisfied, the twist angle of the coolant hole can be made smaller than the twist angle of the outer peripheral blade.

  Therefore, according to the end mill with a coolant hole satisfying the relationship of the formula 2 in addition to the formula 1, the coolant hole is weakly twisted, so that the manufacture of the material of the end mill body is facilitated and the coolant hole is formed. As a result, the volume of the end mill body is reduced and the end mill rigidity can be secured because the volume of the end mill is reduced. On the other hand, the length of the coolant hole is shortened, so pressure loss is reduced and more efficient coolant supply is promoted. Is possible.

  As described above, according to the present invention, even if the end mill body is re-polished, the coolant hole can always be opened in the gash so as to face the bottom blade and its rake face. By directly injecting the coolant toward the surface, efficient cooling and lubrication can be achieved and stable cutting can be performed.

It is a perspective view which shows one Embodiment of this invention. It is a side view of embodiment shown in FIG. It is an enlarged front view of embodiment shown in FIG. FIG. 2 is a perspective view when the embodiment shown in FIG. 1 is re-polished once by a radius R (mm). It is a side view when the embodiment shown in FIG. 1 is re-polished once by a radius R (mm). FIG. 2 is an enlarged front view when the embodiment shown in FIG. 1 is re-polished once by a radius R (mm). FIG. 5 is a perspective view when the embodiment shown in FIG. 1 is re-polished twice for each radius R (mm) (when re-polishing is further performed once for the radius R (mm) from the state of FIG. 4). FIG. 5 is a side view when the embodiment shown in FIG. 1 is re-polished twice for each radius R (mm) (when re-polishing is further performed once for the radius R (mm) from the state of FIG. 4). FIG. 5 is an enlarged front view when the embodiment shown in FIG. 1 is re-polished twice for each radius R (mm) (when re-polishing is further performed once for the radius R (mm) from the state of FIG. 4). It is an enlarged front view which shows the modification of embodiment shown in FIG. FIG. 11 is an enlarged front view when the modification shown in FIG. 10 is re-polished once by a radius R (mm) (when N = 2).

  1 to 9 show an embodiment when the present invention is applied to a ball end mill. In the present embodiment, the end mill main body 1 is integrally formed in a substantially cylindrical shape centering on the axis O with a hard material such as cemented carbide, and its rear end (upper right portion in FIGS. 1, 4, and 7). 5 and 8, the right portion is a cylindrical shank portion 2 and a tip portion (lower left portion in FIGS. 1, 4, and 7. In FIGS. 2, 5, and 8. Is the cutting edge 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, and sent out in a direction intersecting the axis O, The workpiece is cut by the cutting edge portion 3.

  The cutting blade portion 3 has a plurality of chip discharge grooves 4 that are twisted at constant equal twist angles around the axis O toward the rear side in the end mill rotation direction T in the circumferential direction from the front end toward the rear end. Outer peripheral blades 5 having a rake face as the wall surface are formed on the outer peripheral side ridge lines of the wall surfaces that are formed at equal intervals and face the end mill rotation direction T of the chip discharge grooves 4. Here, in the present embodiment, four chip discharge grooves 4 are formed in the cutting edge portion 3, and accordingly, the four outer peripheral blades 5 are equally spaced from each other at equal intervals in the circumferential direction. It is formed with a twist angle, that is, with constant leads Lp (mm) equal to each other.

  Further, a groove-like gash 6 is formed at the tip of each chip discharge groove 4 so as to further cut the tip of the chip discharge groove 4 toward the inner peripheral side. A bottom edge 7 having a rake face as the wall surface is formed at the tip side ridge line portion of the wall surface facing the rotation direction T, respectively. Here, the bottom blade 7 of the present embodiment, which is a ball end mill, has a hemispherical shape in which the rotation locus around the axis O has a center on the axis O and protrudes toward the tip side. The gash 6 is also formed so as to incline toward the rear side in the end mill rotation direction T so as to match the twist of the outer peripheral blade 5 and the chip discharge groove 4 from the inner peripheral side of the front end toward the outer peripheral side of the rear end.

  In the present embodiment, these gashs 6 are bottoms having a rake face as a wall surface facing the end mill rotation direction T when viewed from the front end side in the axis O direction as shown in FIGS. Gash 6A, 6C extending beyond the axis O along the blades 7A, 7C and Gash 6B, 6D not exceeding the axis O are alternately arranged in the circumferential direction. That is, the gashes 6A and 6C are cut out at the inner peripheral portion of the portion serving as the tip flank of the bottom blades 7B and 7D with the above-mentioned wall surface of the gashes 6B and 6D adjacent to the end mill rotation direction T side as a rake face. It communicates with the gashes 6B and 6D.

  Accordingly, the bottom blades 7A and 7C having the wall surface facing the end mill rotation direction T of the gashes 6A and 6C as a rake face extend from the vicinity of the axis O to the outer peripheral side of the rear end in the inner peripheral portion of the front end of the cutting blade portion 3. The bottom blades 7B and 7D, which are long bottom blades and have the wall surfaces facing the end mill rotation direction T of the gash 6B and 6D as rake faces, are rearward from a position farther from the axis O than the bottom blades 7A and 7C. It is a short bottom blade extending to the end outer peripheral side.

  Further, a wall surface facing the rear surface in the end mill rotation direction T is formed in the gasche 6 so as to face the wall surface to be the rake face, and this wall surface is formed in the end mill body 1 as shown in FIG. The coolant hole 8 formed so as to extend from the rear end surface of the shank portion 2 toward the front end side is opened. Here, in this embodiment, the same number of chip discharge grooves 4, outer peripheral blades 5, bottom blades 7, and gashes 6, that is, a plurality of four coolant holes 8 are formed at equal intervals in the circumferential direction. Each of the wall surfaces facing the rear side in the end mill rotation direction T is opened.

  Further, these coolant holes 8 are formed so as to be located inside the core thick circle centering on the axis O inscribed in the bottom surface of the chip discharge groove 4 in the cross section orthogonal to the axis O of the end mill body 1. That is, the plurality of coolant holes 8 are positioned at equal intervals in the circumferential direction as described above on the circumference centered on the axis O having a constant diameter smaller than the thick circle. Each coolant hole 8 is substantially circular in a cross section orthogonal to the axis O.

  These coolant holes 8 are fixed leads Lh in a direction opposite to the chip discharge grooves 4 and the outer peripheral blade 5, and in the present embodiment, in a direction toward the end mill rotation direction T side toward the rear end side in the axis O direction. The lead Lh (mm) of the coolant hole 8 is formed from the lead Lp (mm) of the outer peripheral blade 5 and the axis O of the end mill body 1 to the outer peripheral end of the bottom blade 7. Of the hemisphere formed by the rotation trajectory of the bottom blade 7 around the axis O, the number of blades Z of the bottom blade 7, and an integer N of 1 or more, Have been to have.

  Further, in this embodiment, the lead Lp (mm) of the outer peripheral blade is the same as the equation (1), the radius R (mm) from the axis O to the outer peripheral end of the bottom blade, the number Z of blades of the bottom blade, and the like. The relationship of the following formula 2 is satisfied for an integer N of 1 or more.

  In order to manufacture the end mill body 1 of such an end mill with a coolant hole by using a powder sintered alloy such as cemented carbide as described above, for example, a mixture of a raw material alloy powder and a binder is mixed inside. A cylindrical sintered alloy material having a through hole twisted around the axis to be the coolant hole 8 is first molded by rotating from a nozzle of an extrusion molding machine provided with the same number of pins as the coolant hole 8. .

  Then, after sintering this sintered alloy material, the gash 6 is formed so that the coolant hole 8 opens in the wall surface facing the rear side in the end mill rotation direction T, and the ridge line on the tip side of the wall surface facing the end mill rotation direction T is formed. The bottom blade 7 may be formed in the portion, and the chip discharge groove 4 may be formed so that the outer peripheral edge 5 is connected to the outer peripheral end of the bottom blade 7. At this time, the lead Lh (mm) of the coolant hole 8 determines the extrusion speed and the rotation speed of the sintered alloy material from the nozzle of the extrusion molding machine while considering the shrinkage rate when the sintered alloy material is sintered. By controlling, it can set so that the said Formula 1 may be satisfy | filled.

  In such an end mill with a coolant hole, as the coolant hole 8 is directed from the wall surface facing the rear side in the end mill rotation direction T of the gash 6 toward the rear end side, the axis O is directed toward the end mill rotation direction T opposite to the outer peripheral blade 5. It is formed so as to be twisted around and is opened in the wall surface. Conversely, the opening toward the wall surface extends toward the rear side in the end mill rotation direction T.

  That is, the opening on the front end side of the coolant hole 8 is opposed to the wall surface or bottom blade 7 that is the scoop surface of the gash 6 directed toward the end mill rotation direction T, and the front end of the coolant hole 8 in the vicinity of the opening. Since the extension line to the side is formed so as to intersect the surface of the bottom blade 7 that is easy to intersect with an angle, the coolant is easy to bottom the edge, for example, when the extension line extends along the rake face. Compared with the case where the surface is squirted and sprayed, the coolant can be sprayed more directly and in a large amount so that the coolant hits the bottom blade 7 and its rake face.

  Therefore, according to the end mill with the coolant hole having the above-described configuration, it is possible to efficiently cool and lubricate the surface that is easy to have the bottom blade 7, and the wear of the bottom blade 7 is significantly progressed by the heat generated during cutting. It is possible to prevent the occurrence of welding on the surface and reduce cutting resistance, and promote stable cutting over a long period of time. In particular, in the present embodiment, the gash 6 and the bottom blade 7 are formed so as to be inclined in the same direction as the twist direction of the chip discharge groove 4 and the outer peripheral blade 5, so that the extension line of the coolant hole 8 has a larger angle. Thus, the bottom blade 7 can be made to intersect with a surface that is easy to achieve, and more efficient cooling and lubrication can be achieved.

  Furthermore, in the end mill with the coolant hole having the above-described configuration, the lead Lh (mm) of the coolant hole 8 extends from the lead Lp (mm) of the outer peripheral blade 5 and the axis O of the end mill body 1 to the outer peripheral end of the bottom blade 7. Since there is a relation of the above formula 1 with respect to the radius R (mm), the number of blades Z of the bottom blade 7, and an integer N of 1 or more, re-polishing like the ball end mill of this embodiment. In this case, when the end mill main body 1 is polished and retracted by the amount of the hemisphere formed by the rotation trajectory of the bottom blade 7, that is, the tip end portion of the cutting edge 3 of the end mill main body 1 is re-polished with the same amount of radius R (mm). When retreating, the opening of the coolant hole 8 is rotated in the direction of end mill rotation of the gash 6 formed after re-polishing in the chip discharge groove 4 connected to the gash 6 opened before re-polishing according to the integer N. T back side Ku the wall or to this, can be opened in the same wall of different gashes 6.

  For example, the embodiment shown in FIG. 1 to FIG. 9 is an example in the case where the integer N = 1 in the expression 1, but the cutting edge portion 3 is re-polished from the state shown in FIG. 1 to FIG. As shown in FIGS. 4 to 6, the tip of the cutting edge 3 is moved backward by the radius R (mm) toward the rear end in the direction of the axis O, and before the re-grinding with respect to the chip discharge groove 4 and the outer peripheral edge 5. When the gash 6 and the bottom blade 7 are formed so as to have the same positional relationship, as shown in FIG. 3, the coolant holes 8A opened in the wall surfaces facing the rear side in the end mill rotation direction T of the gashes 6A to 6D before re-grinding as shown in FIG. -8D in order, as shown in FIG. 6, the end mill rotation direction T of the gashes 6B, 6C, 6D, 6A formed on the tip end side of the chip discharge groove 4 adjacent to the end mill rotation direction T side after repolishing one by one. It can be opened on the wall facing backward It becomes door.

  4 to 6, the second re-polishing is performed, and the tip of the cutting edge portion 3 is further moved by the radius R (mm) in the direction of the axis O as shown in FIGS. When the gash 6 and the bottom blade 7 are formed while retreating to the end side, the wall faces the rear side in the end mill rotation direction T of the gash 6B, 6C, 6D, 6A as shown in FIG. 6 before the second re-polishing. As shown in FIG. 9, the coolant holes 8A to 8D that have been opened in each are formed one by one on the tip side of the chip discharge groove 4 adjacent to the end mill rotation direction T side after the second regrind. The gash 6C, 6D, 6A, 6B is opened on the wall surface facing the rear side in the end mill rotation direction T. Accordingly, if re-polishing is performed four times, the coolant holes 8A to 8D return to the gashes 6A to 6D formed on the tip side of the original chip discharge groove 4.

  And since the lead Lh (mm) is constant in the coolant hole 8 opened on the wall surface facing the rear side in the end mill rotation direction T of each gash 6 after each re-grinding in this way, both of them are the same as before re-polishing. The opening on the tip side faces the wall surface of the bottom blade 7 and the gash 6 facing the end mill rotation direction T and is the rake face of the bottom blade 7, and extends to the tip side of the coolant hole 8 in the vicinity of the opening. The line is formed so as to intersect the bottom blade 7 and its rake face with an angle. Therefore, according to the end mill with a coolant hole having the above-described configuration, it is possible to maintain the above-described efficient cooling and lubrication effect regardless of before and after the re-polishing, and it is easy to suppress the wear of the bottom blade 7 over a long period of time. It is possible to prevent welding to the surface or reduce cutting resistance.

  FIGS. 1 to 9 illustrate the case where the integer N = 1 in the equation 1, as described above. When the integer N = 2, the lead Lh (mm) of the coolant hole 8 is calculated based on the equation 1. 3, the first regrind is performed from the state shown in the front view of FIG. 3, and the tip of the cutting edge 3 is moved backward by the radius R (mm) toward the rear end in the direction of the axis O, and the gash 6 and the bottom When the blade 7 is formed, the coolant holes 8A to 8D that have been opened in the gashes 6A to 6D before re-polishing are sequentially turned in the end mill rotation direction T side by two as shown in the front view shown in FIG. Is opened on the wall surface facing the rear side in the end mill rotation direction T of the gashes 6C, 6D, 6A, 6B formed on the tip side of the chip discharge groove 4 adjacent to the chip.

  In the present embodiment, as described above, the same number of coolant holes 8 are formed for the plurality (four) of the gash 6 and the bottom blade 7, and when the integer N = 1 in Equation 1, A coolant hole 8 is opened in the gash 6 formed on the tip side of the chip discharge groove 4 on the end mill rotation direction T side for each polishing, but as in the modification shown in FIGS. 10 and 11. The number Z of the bottom blades 7 and the number of the coolant holes 8 may be different.

  Here, in this modified example, before re-grinding, for example, the rake faces of the bottom blades 7A and 7C, which are the long bottom blades, are opened only on the wall surface facing the rear side in the end mill rotation direction T of the gashes 6A and 6C. As shown in FIG. 10, two coolant holes 8A and 8C smaller than the bottom blade 7 are formed as shown in FIG. However, as shown in FIG. 11, the gashes 6C and 6A formed on the tip end side of the chip discharge groove 4 adjacent to the end mill rotation direction T side by side as shown in FIG. ing.

  In such a modified end mill with a coolant hole, it is possible to achieve efficient and intensive cooling and lubrication of the bottom blades 7A and 7C and the rake face thereof, which are particularly long bottom blades with a heavy burden during cutting, On the other hand, since the gash 6A, 6C in which the coolant holes 8A, 8C are opened communicates with the remaining gash 6B, 6D as described above, the wall surface used as the rake face of these gash 6B, 6D and A certain amount of cooling and lubricating effects can also be given to the bottom blades 7B and 7D, which are short bottom blades with a small burden during cutting. On the other hand, since this modification can reduce the number of coolant holes 8 formed in the end mill body 1, the rigidity of the end mill body 1 can be improved.

  Further, in the present embodiment, the lead Lh (mm) of the coolant hole 8 satisfies the relationship of the above formula 1, and the lead Lp (mm) of the outer peripheral blade 5 further extends from the axis O to the outer peripheral end of the bottom blade 7. The radius R (mm), the number of blades Z of the bottom blade 7 and the integer N equal to or greater than 1 are set so as to satisfy the relationship of the above formula 2. Thus, the twist angle of the coolant hole 8 can be reduced. The rigidity of the end mill main body 1 is also improved by making it smaller than the twist angle of the outer peripheral blade 5 and reducing the amount by which the volume of the end mill main body 1 is reduced by the coolant hole 8.

  For example, when the radius R from the axis O to the outer peripheral edge of the bottom blade 7 is 3 (mm), the number Z of the bottom blades 7 is 4, and the integer N is 1 or more, the twist angle of the outer peripheral blade 5 is When it is 30 °, the lead Lp of the outer peripheral blade 5 is 32.65 (mm) and does not satisfy the formula 2. At this time, the lead Lh of the coolant hole 8 is 18.97 (mm), and the twist angle of the coolant hole 8 is 44.81 °, which is larger than the twist angle of the outer peripheral blade 5, but when the twist angle of the outer peripheral blade 5 is 45 °, the lead Lp of the outer peripheral blade 5 = 18.85 (mm) and Equation 2 is obtained. Will meet.

  At this time, the lead Lh of the coolant hole 8 is 33.02 (mm), and the twist angle of the coolant hole 8 is 29.72 °, which is significantly smaller than the twist angle of the outer peripheral blade 5. Therefore, according to the end mill with a coolant hole satisfying the above formula 2, the total length of the coolant hole 8 can be shortened by reducing the torsion angle of the coolant hole 8, and the volume of the end mill body 1 is reduced by opening the coolant hole 8. Therefore, it is possible to provide an end mill with a coolant hole with higher rigidity.

  Further, since the total length of the coolant hole 8 is shortened, pressure loss when supplying the coolant can be reduced, and more efficient cooling and lubrication can be achieved. In addition, since the torsion angle of the coolant hole 8 is reduced in this way, when the end mill body 1 is manufactured from the sintered alloy material obtained by extruding the mixture of the alloy powder and the binder as described above, Since the rotational speed applied when the gold material is formed can be reduced, it is not necessary to forcibly twist and extrude the sintered alloy material, making it easy to manufacture the material.

  In the present embodiment, the number of coolant holes 8 is the same as the number of blades Z = 4 of the bottom blade 7, and in the modified example, the number of coolant holes 8 is also the same as the number of blades Z = 4 of the bottom blade 7. The number of coolant holes 8 may be one, for example, as long as the above equation 1 is satisfied. Similarly, the number of the coolant holes 8 may be 1 or 2 in the two-blade end mill with the number Z = 2 of the bottom blade 7, and the six-blade end mill with the number Z = 6 of the bottom blade 7. The number of the coolant holes 8 may be 1, 2, 3, 6, and the number of the coolant holes 8 may be 1, 2, 4, 8, etc. in an 8-flute end mill with the number of blades Z = 8 of the bottom blade 7.

  However, in such a multi-blade end mill with the number of blades Z = 6 or Z = 8 of the bottom blade 7, if more coolant holes 8 are formed by the radius R (mm) of the bottom blade 7, the rigidity of the end mill body 1 is increased. In a case where it cannot be ensured, the number of coolant holes 8 is preferably a divisor of this number of blades Z including 1 and the number of blades Z itself.

  On the other hand, when the rigidity of the end mill main body 1 can be sufficiently secured, in addition to the coolant hole 8 that satisfies the above formula 1 and opens on the wall surface facing the rear side in the end mill rotation direction T of the gash 6, for example, the formula Although 1 is satisfied, it does not open in the gash 6, but forms other coolant holes that open from the axis O at the same radius as the coolant hole 8 on the tip flank of the bottom blade 7 adjacent in the circumferential direction. Alternatively, a larger number of coolant holes than the number of the bottom blades 7 may be formed.

  That is, for example, in a four-blade end mill such as the embodiment shown in FIGS. 1 to 9, the coolant holes 8A are interposed between the four coolant holes 8A to 8D adjacent in the circumferential direction. A position that equally divides the position in the circumferential direction of ˜8D (a straight line that connects the coolant holes 8A to 8D and the axis O on the circumference having the same radius as the coolant holes 8A to 8D around the axis O in FIG. 3) The other coolant hole of the lead Lh (mm) equal to the coolant hole 8 is formed so as to open on the flank (tip flank) of the bottom blade 7 at a position on the radial line forming 45 ° with respect to Also good.

  In this case, from the state shown in FIGS. 1 to 3, the tip of the cutting edge portion 3 is half R / 2 (mm) with respect to the radius R (mm) from the axis O to the outer peripheral edge of the bottom blade 7. If regrinding is performed so that the part moves backward, another coolant hole opened on the tip flank before regrinding opens in the gash 6 of the bottom blade 7 adjacent to the end mill rotation direction T side. As a result, the end mill body 1 can have a long life by reducing the amount of re-polishing once.

  In the above embodiment, the case where the present invention is applied to a ball end mill with a coolant hole has been described. However, the present invention is a solid end mill in which a bottom blade and an outer peripheral blade are substantially orthogonal, and thus substantially orthogonal. Of course, it is also possible to apply to a radius end mill in which an arcuate corner blade is formed at the intersection of the bottom blade and the outer peripheral blade. Here, in the case of this radius end mill, the radius R (mm) from the axis O to the outer peripheral end of the bottom blade may be a radius to the outer peripheral end of the bottom blade including the corner blade.

  Further, in the above embodiment, the description has been given of the equal-lead equally-divided end mill in which the plurality of outer peripheral blades 5 and the bottom blade 7 are all formed at equal intervals in the circumferential direction and the leads Lp (mm) are equal to each other. In the modification shown in FIGS. 10 and 11, the bottom blades 7B and 7D, which are short bottom blades, and the outer peripheral blades 5 connected to these are formed at unequal intervals in the circumferential direction, and are used as unequal division end mills. In addition, even in the bottom blades 7B and 7D thus divided equally and the bottom blades 7B and 7D thus equally divided, the leads of the outer peripheral blade 5 connected to the bottom blades 7B and 7D are the bottom blades 7A and 7C. The lead may be a lead different from the lead Lp (mm) of the outer peripheral blade 5, and may be an unequal lead end mill.

DESCRIPTION OF SYMBOLS 1 End mill main body 2 Shank part 3 Cutting blade part 4 Chip discharge groove 5 Peripheral blade 6 (6A-6D) Gash 7 (7A-7D) Bottom blade 8 (8A-8D) Coolant hole O Axis line of end mill main body T End mill rotation direction

Claims (2)

A chip discharge groove that twists around the axis is formed on the outer periphery of the tip of the end mill body that rotates about the axis, and a gash is formed on the tip side of the chip discharge groove, and the wall faces the end mill rotation direction of the gasche A bottom blade is formed at the tip side ridge line portion, and an outer peripheral blade twisted with a constant lead Lp (mm) around the axis from the outer peripheral end of the bottom blade toward the rear end side of the end mill body. On the other hand, from the gasche toward the rear end side of the end mill body, there is a coolant hole twisted with a constant lead Lh (mm) around the axis in the direction opposite to the outer peripheral blade. The coolant hole lead Lh (mm) is formed so as to extend in a circle, and the outer peripheral blade lead Lp (mm) and the radius R (mm) from the axis to the outer peripheral edge of the bottom blade , The bottom and the number of teeth Z of the blade, one or more relative to the integer N, the coolant slotted end mill, characterized in that it has a relation of the following equation 1.

The lead Lp (mm) of the outer peripheral blade is the following with respect to a radius R (mm) from the axis to the outer peripheral edge of the bottom blade, the number of blades Z of the bottom blade, and the integer N of 1 or more. The end mill with a coolant hole according to claim 1, wherein the relationship of Formula 2 is satisfied.

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