JP5447068B2 - End mill with coolant hole - Google Patents

Description

  The present invention relates to an end mill with a coolant hole in which a coolant hole is opened at a tip portion of an end mill body.

  As such an end mill with a coolant hole, Patent Documents 1 and 2 have proposed that a coolant hole formed in a spiral shape in the end mill body is opened on the bottom surface of the end of the end mill body. Among these, Patent Document 1 describes that the coolant hole may not be spiral but may be straight, and further, a trunk hole formed along the axis of the end mill body is branched at the tip portion. There is also known one in which the branched branch hole is opened at the end of the end mill body.

JP-A-8-318419 JP 2001-025915 A

  However, as described above, it is difficult to accurately open the coolant hole formed in a spiral shape in the end mill body at a predetermined position on the bottom surface of the gash. Especially in an end mill having a small cutting edge diameter, a high-magnification camera, etc. May be required. In addition, even in the coolant hole thus formed in a spiral shape or a straight coolant hole, the shape of the opening is usually circular like the cross-sectional shape of the coolant hole, and the opening area is also the cross-sectional area of the coolant hole. Therefore, the coolant supplied from the rear end portion of the end mill body loses the injection pressure due to the pressure loss, and it becomes difficult to inject the coolant over a wide range. This is the same when the branch hole is branched from the trunk hole along the axis and the total opening area of the branch holes is relatively large with respect to the cross-sectional area of the trunk hole.

  The present invention is made under such a background, and it is possible to easily open the coolant hole to a predetermined position on the bottom surface of the gash, and to inject the coolant from the opening at a high pressure over a wide range. It aims at providing the end mill with a coolant hole which can be made to do.

  In order to solve the above problems and achieve such an object, according to the present invention, a gash is formed at a tip portion of an end mill body rotated around an axis, and the end mill body is along the axis. The coolant hole is formed by the outer peripheral edge portion of the bottom surface of the coolant hole at the tip end side of the end mill body partially intersecting the bottom surface of the gasche facing the outer peripheral side of the tip of the gasche. It is characterized by being opened at the bottom of the gash.

  In such an end mill, the gash is a groove formed so as to cut out the tip end portion of the chip discharge groove formed on the outer peripheral portion of the end mill body toward the inner peripheral side, and the wall surface facing the end mill rotation direction is a bottom blade. The bottom surface facing the tip outer peripheral side of the gasche that intersects with the rake surface is inclined so as to go to the inner peripheral side as it goes to the tip side. Therefore, when the coolant hole is drilled along the axis of the end mill body, the gashash is determined by the inner diameter of the coolant hole and the depth, that is, the position of the bottom surface of the coolant hole in the axial direction regardless of the outer diameter of the cutting edge. The opening position to the bottom is accurately set.

  And the opening part of the coolant hole opened to the bottom face of the gash in this way has an opening area smaller than the cross-sectional area of the coolant hole because the outer peripheral edge part of the coolant hole bottom part partially intersects the gash bottom face. Therefore, it becomes possible to inject the coolant at a high pressure. Furthermore, the opening of the coolant hole is formed so as to open to the gash bottom surface in an arc shape extending in the circumferential direction along the outer peripheral edge of the coolant hole bottom surface, and therefore from the wall surface of the gash serving as the scoop surface of the bottom blade. The coolant can be supplied in a wider range toward the end mill rotating direction side.

  Here, the opening in the gash bottom surface of the coolant hole extending in an arc shape in this way, the radial opening width is gradually increased especially from the both ends in the circumferential direction as viewed from the axial front end side. In other words, it is desirable to form a crescent shape when viewed from the front in the axial direction. As a result, more coolant injection amount can be secured at the center portion in the circumferential direction of the coolant hole opening portion where the opening width is widened, and more efficient coolant supply can be achieved. By suppressing this, it is possible to avoid a decrease in injection pressure due to an excessively large opening area.

  Further, by making the bottom surface of the coolant hole flat at least on the outer peripheral edge side, it is possible to accurately grasp the position in the axial direction of the bottom surface of the coolant hole. It becomes possible to set the opening position and the shape and size of the opening more accurately. On the other hand, by forming the bottom surface of the coolant hole so as to have a convex portion that protrudes at the rear end side in the axial direction on at least the central portion side, the thickness of the end mill main body on the central portion side is increased. It is possible to secure and prevent damage to the end mill body due to cutting load or the like.

  As described above, according to the present invention, the opening of the coolant hole can be accurately opened at a predetermined position on the gash bottom surface, and the coolant can be sprayed from the opening at a high pressure over a wide range. This makes it possible to reliably and efficiently cut and lubricate the cutting edge and the part to be cut, and discharge chips.

It is a side view which shows the 1st Embodiment of this invention. It is the rear view which looked at embodiment shown in FIG. 1 from the axial direction rear end side. It is the enlarged front view which looked at embodiment shown in FIG. 1 from the axial direction front end side. It is an enlarged side view of the front-end | tip part of embodiment shown in FIG. It is an enlarged side view of the front-end | tip part of the 2nd Embodiment of this invention.

  1 to 4 show a first embodiment of the present invention. In the end mill of the present embodiment, the end mill body 1 has a rear end portion (right side portion in FIG. 1) as a cylindrical shank portion 2 centering on the axis O as shown in FIG. A cutting blade portion 4 is integrally formed on the distal end side (left side in FIG. 1) via a tapered portion 3 whose outer diameter gradually decreases toward the distal end side. In such an end mill, the shank portion 2 is gripped by a main shaft of a machine tool (not shown), and is rotated in the end mill rotation direction T around the axis O, and is sent in a direction intersecting the axis O, so that the cutting blade portion 4 To cut the work material.

  A plurality of strips (two strips in this embodiment) are twisted on the outer peripheral surface of the cutting edge portion 4 toward the distal end side of the tapered portion 3 and twisted toward the rear side in the end mill rotation direction T toward the rear side in the axis O direction. A discharge groove 5 is formed, and an outer peripheral edge 6 is formed on an outer peripheral side ridge of the wall surface facing the end mill rotation direction T side. In the end mill main body 1 of the present embodiment, the cutting edge portion 4 is formed to be 180 ° rotationally symmetric with respect to the axis O.

  Further, on the tip side of these chip discharge grooves 5, a gash 7 is formed so as to cut out the tip part of the chip discharge groove 5 toward the inner peripheral side as it goes further toward the tip side in the axis O direction. Further, at the intersecting ridge line portion between the wall surface 7A facing the end mill rotation direction T of the gasche 7 and the front end surface of the end mill body 1, the wall surface 7A is used as a rake surface and the front end surface is a flank (front end flank). A bottom blade 8 is formed.

  Here, in the present embodiment, the bottom blade 8 has a hemispherical shape in which the rotation trajectory around the axis O has a center on the axis O and is convex toward the tip, that is, the book The end mill of the embodiment is a ball end mill. Further, the outer peripheral blade 6 is connected to the outer peripheral ends of these bottom blades 8, and in the present embodiment, the rotation locus around the axis O is formed into a cylindrical surface having a radius equal to the radius of the hemisphere.

  On the other hand, a coolant hole 10 is formed in the end mill body 1 from the rear end surface 9 along the axis O toward the front end side. In this embodiment, the coolant hole 10 has a circular cross section with a constant inner diameter centered on the axis O, and this inner diameter is based on the core thickness from the axis O to the groove bottom of the chip discharge groove 5 in the cutting edge portion 4. The coolant hole bottom surface 10A is provided in the range where the gash 7 is formed in the direction of the axis O in front of the cutting edge 4 without reaching the center of rotation intersecting the axis O at the tip of the cutting edge 4. Has been.

  The coolant hole 10 has an outer peripheral edge portion of the coolant hole bottom surface 10A, that is, an intersecting ridge line portion between the coolant hole bottom surface 10A and the inner peripheral surface of the coolant hole 10 from the wall surface 7A of the gash 7 to the end mill body 1. The gash bottom surface 7 </ b> B extending in the end mill rotation direction T toward the tip outer peripheral side is partially intersected. Accordingly, the opening portion 10B of the coolant hole 10 is opened in the arcuate shape extending along the circumference formed by the outer peripheral edge portion of the coolant hole bottom surface 10A.

  Here, the coolant hole bottom surface 10A has a planar shape in which at least the outer peripheral edge side is perpendicular to the axis O. In particular, in the present embodiment, the entire surface is a plane perpendicular to the axis O. On the other hand, the gash bottom surface 7B has a convex curved surface shape that slightly curves toward the outer periphery of the tip while inclining toward the inner periphery as it goes toward the tip of the axis O direction, and also curves in the circumferential direction. Accordingly, the opening 10B is seen in the direction of the axis O direction as shown in black in FIG. 3, and both ends of the arc along the inner peripheral surface of the coolant hole 10 are arc-shaped or linear with a radius larger than the radius of the arc. A crescent moon like that tied with a string of.

  In the end mill configured as described above, when the work material is cut as described above, the coolant is supplied from the machine tool side to the coolant hole 10 opened in the rear end surface 9 of the end mill body 1, and the cutting blade It is made to spray from the opening part 10B opened to the opening to the gash bottom face 7B of the part 3. Here, in the end mill configured as described above, the coolant hole 10 formed in the end mill body 1 does not open to the gash bottom surface 7B with the same inner diameter, but the outer peripheral edge of the coolant hole bottom surface 10A is partially gashed. The opening 10B is opened across the bottom surface 7B, and the opening area of the opening 10B is smaller than the cross-sectional area of the coolant hole 10 even if all the openings 10B are combined.

  Therefore, the coolant can be injected at a high pressure from the opening 10B of the gash bottom surface 7B, and the wall surface 7A of the gash 7 serving as the rake face of the bottom blade 8 connected to the rear side in the end mill rotation direction T of the gash bottom surface 7B. Further, coolant can be effectively supplied to the cutting edge of the work material by the bottom blade 8 itself and the bottom blade 8, and cooling and lubrication thereof can be achieved. Further, chips generated by the bottom blade 8 at the time of cutting can be smoothly discharged by the coolant sprayed from the opening 10B.

  Further, the opening 10B of the coolant hole 10 thus opened to the gash bottom surface 7B is formed so that the outer peripheral edge of the coolant hole bottom 10A partially intersects the gash bottom 7B. In other words, the coolant hole bottom surface 10A and the inner peripheral surface of the coolant hole 10 are formed so as to extend in the circumferential direction in an arc shape along the intersecting ridge line portion. Therefore, the coolant can be injected so as to spread over a wider range in the circumferential direction, and further reliable cooling and lubrication and chip discharge can be promoted.

  Further, in order to open the coolant hole 10 in the gash bottom surface 7B in this way, in the end mill configured as described above, the outer peripheral edge portion of the bottom surface 10A of the coolant hole 10 drilled along the axis O in this way is partially formed in the gash bottom surface 7B. The position and size of the opening 10B are independent of the outer diameter of the bottom blade 8 depending on the inner diameter of the coolant hole 10 relative to the gash bottom surface 7B and the position of the coolant hole bottom surface 10A in the axis O direction. Can be set accurately and easily.

  For this reason, even if the cutting edge portion 4 has a small diameter reduced from the shank portion 2 via the taper portion 3 as in the present embodiment, the opening portion 10B is surely provided at a predetermined position on the gash bottom surface 7B. Can be formed. It is also easy to open the opening 10B on the inner peripheral side of the front end of the gash bottom surface 7B, conversely open it on the outer peripheral side of the rear end, or increase or decrease the opening area according to the form of cutting. Thus, more effective coolant supply can be achieved.

  Further, in the present embodiment, the opening 10B of the coolant hole 10 opened in this way is such that the opening width in the radial direction gradually increases from the both ends in the circumferential direction to the center as seen from the front end side in the axis O direction. In this way, the amount of coolant spray can be increased in the central portion in the circumferential direction where the opening width is widened. For this reason, as compared with the case where the opening 10B extends in the circumferential direction with a constant opening width, a sufficient coolant injection amount can be secured and efficient supply can be achieved. In the case where the opening width is a constant width, it is possible to avoid a situation in which the opening area becomes too large and the coolant injection pressure is reduced.

  Furthermore, in the present embodiment, the bottom surface 10A of the coolant hole 10 has a planar shape that is perpendicular to the axis O at least on the outer peripheral edge side thereof, and extends from the rear end face 9 of the end mill body 1 to the outer peripheral edge side. It becomes easy to accurately grasp the depth of the coolant hole 10 up to the plane. And in connection with this, the position and inclination of the gash bottom 7B which can confirm the position, shape, and size of the opening 10B that opens when the outer peripheral edge intersects the gash bottom 7B from the outside of the end mill body 1. On the other hand, since it becomes possible to set more accurately from the inner diameter of the coolant hole 10 and the depth of the coolant hole 10, it is possible to promote more reliable and efficient supply of the coolant.

  In the first embodiment, the entire bottom surface 10A of the coolant hole is a plane perpendicular to the axis O. However, as in the second embodiment of the present invention shown in FIG. A convex portion 10C may be formed at the center of the bottom surface 10A. In the second embodiment shown in FIG. 5, the portions other than the shape of the convex portion 10C and the opening 10B associated therewith are the same as those in the first embodiment, and are common to the opening 10B. Elements are given the same reference numerals and description thereof is omitted.

  Here, the convex portion 10C in the second embodiment is formed so as to protrude in the conical shape with the axis O as the center and protrude toward the rear end side, and accordingly, the opening portion 10B of the coolant hole 10 is also formed. As shown in black in FIG. 5, the gash 7 is formed so as to be inclined and extend along a conical generatrix formed by the convex portion 10 </ b> C in a side view facing the wall surface 7 </ b> A. However, as shown in the upper side of FIG. 5, the convex portion 10 </ b> C is formed so as to protrude from a position slightly separated from the outer peripheral edge portion that is an intersecting ridge line portion with the inner peripheral surface of the bottom surface 10 </ b> A of the coolant hole 10. In addition, a bottom surface 10A having a planar shape perpendicular to the axis O is left at the outer peripheral edge.

  In the end mill of the second embodiment configured as described above, in addition to the effect of the first embodiment, at the center portion of the coolant hole bottom surface 10A where the convex portion 10C is formed, the front end surface of the end mill body 1 ( It is possible to ensure a large wall thickness between the tip flank and the flank. For this reason, especially when the present invention is applied to the ball end mill as in this embodiment, the bottom blade 8 is often used for cutting to the center of rotation on the axis O at the end of the end mill body 1. Thus, it is possible to prevent the end mill body 1 from being damaged by a cutting load or the like acting on the rotation center portion.

  Further, if the opening 10B is formed so as to open along the slope of the convex portion 10C, the crossing angle between the slope and the gash bottom surface 7B intersecting via the opening 10B is set to the first embodiment. The coolant hole bottom surface 10A and the gash bottom surface 7B in the form can be made larger than the crossing angle, and the strength at the opening 10B of the coolant hole 10 can be secured to prevent the end mill body 1 from being damaged more reliably. . Furthermore, by forming the convex portion 10C having such a slope, it is possible to adjust the injection angle of the coolant from the opening 10B with respect to the axis O.

  In addition, as a convex part which has such a slope, a truncated cone-shaped convex part and a spherical-shaped convex part may be sufficient. Further, as described above, in order to ensure a large thickness between the center portion of the coolant hole bottom surface 10A and the tip surface (tip flank surface) of the end mill body 1, a disk shape or a circle around the axis O is used. It may be a columnar convex part.

  By the way, in order to form such a coolant hole 10 in the end mill main body 1, for example, after first forming the gash 7 and the bottom blade 8 in the end mill main body 1, the coolant hole 10 is formed along the axis O from the rear end surface 9. However, if the end mill body 1 is formed of a hard material such as cemented carbide as in this embodiment, the drill may be drilled to the depth of This makes it difficult to drill the hole itself, and even if electric discharge machining is performed, a lot of time and labor are required.

  Therefore, when the end mill body 1 is formed of a powder sintered body such as a cemented carbide as described above, a cylindrical shaft-shaped core is used as a press mold when the green compact of the sintered body is formed. Is arranged along the axis O, and the coolant hole 10 is previously formed in the green compact. After sintering, the gash 7 and the bottom blade 8 are formed, and the bottom surface 7B of the gash 7 is formed. What is necessary is just to make it the coolant hole 10 open. At this time, if the tip end surface of the core is a plane perpendicular to the axis O, the coolant hole bottom surface 10A is also a plane perpendicular to the axis O as in the first embodiment, and the tip end surface of the core is recessed. If it has a conical surface shape, the convex portion 10C as in the second embodiment can be formed.

  Even when the coolant hole 10 is formed in the end mill body 1 in advance as described above, or when the coolant hole 10 is formed in the end mill body 1 in which the gash 7 and the bottom blade 8 are formed, the cylindrical shaft The axis of the tool body is rotated relative to the end mill body 1 around the axis O using a grinding tool in which an abrasive layer containing diamond abrasive grains or the like is formed on the surface of at least the tip of the shaped tool body. The coolant hole 10 may be sent along O to finish the coolant hole 10 formed in advance, or the coolant hole 10 itself may be formed in the end mill body 1 itself. Also in this case, if the tip surface of the tool body is a plane perpendicular to the axis O, the coolant hole bottom surface 10A is also a plane perpendicular to the axis O as in the first embodiment, and the tip surface of the tool body is If the concave conical surface is used, the convex portion 10C as in the second embodiment can be formed.

  In the first and second embodiments, the case where the present invention is applied to a ball end mill in which the rotation trajectory of the bottom blade 8 forms a hemispherical shape has been described. However, if a gash is formed at the end of the end mill main body. The present invention is applied to a square end mill formed so that the bottom blade extends in a direction substantially perpendicular to the axis O, and a radius end mill in which the bottom blade and the outer peripheral blade are connected by a quarter arc-shaped corner blade. It is also possible to apply. Furthermore, in the said 1st, 2nd embodiment, the cutting-blade part 4 is formed in rotational symmetry with respect to the axis line O, and the bottom blade 8 and the outer periphery blade 6 are arrange | positioned at equal division in the circumferential direction. They may be arranged in unequal divisions or formed to have different twist angles.

1 End mill body 7 Gash 7A Wall surface facing the end mill rotation direction T of Gash 7 (rake face of bottom blade 8)
7B Bottom surface facing the outer peripheral side of the tip of the gash 7 8 Bottom blade 10 Coolant hole 10A Bottom surface of the coolant hole 10B Opening portion of the coolant hole 10 to the gash bottom surface 7B 10C Convex portion O Axis of end mill body 1 T End mill rotation direction

Claims (4)

  A gash is formed at the tip of the end mill body rotated about the axis, and a coolant hole is formed along the axis in the end mill body. The coolant hole is located on the tip side of the end mill body. An end mill with a coolant hole, characterized in that an outer peripheral edge portion of a bottom surface of the coolant hole partially opens with a bottom surface of the gasche facing the outer peripheral side of the tip of the gasche, thereby opening the gash bottom surface.   2. The opening of the coolant hole at the gash bottom surface has a gradually increasing opening width in the radial direction from both ends in the circumferential direction toward the center as viewed from the tip end in the axial direction. End mill with coolant hole as described in 1.   3. The end mill with coolant holes according to claim 1, wherein the bottom surface of the coolant hole has a planar shape perpendicular to the axis at least on the outer peripheral edge side. 4.   The coolant according to any one of claims 1 to 3, wherein the bottom surface of the coolant hole has a convex portion that protrudes toward the rear end side in the axial direction at least in a central portion thereof. End mill with holes.

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