JP2006082111A - Extrusion press forming method of shaft body with spiral hole, shaft material with spiral hole, and small diameter drill with spiral hole - Google Patents

Abstract

PROBLEM TO BE SOLVED: To form a spiral hole with high lead length accuracy without requiring a complicated mold or high press pressure when extruding and pressing a shaft body with a spiral hole in order to manufacture a drill with a spiral hole having a small diameter. The formed shaft-like body is securely molded.
SOLUTION: Extrusion press molding of a shaft-shaped body with a spiral hole for forming a shaft-shaped body A in which a spiral hole B is formed by extruding a press raw material from an inner peripheral portion 1A of a cylindrical mold 1 In the mold 1, a linear body 11 that forms a screw hole B is provided in a position eccentric from the center line O of the inner peripheral portion 1 </ b> A of the mold 1, and the inner peripheral surface of the mold 1. A groove 1 </ b> C extending in the direction of the center line O is formed in 1 </ b> B, and the shaft-shaped body A is formed by extruding the press raw material while rotating the mold 1 around the center line O.
[Selection] Figure 1

Description

  The present invention relates to an extrusion press molding method for a shaft body with a spiral hole, which is particularly suitable for manufacturing a small-diameter spiral hole drill, and a spiral manufactured from a shaft body with a spiral hole formed by this extrusion press molding method. The present invention relates to a shaft-shaped material with a hole, and a small-diameter drill with a spiral hole manufactured from a shaft-shaped body with a spiral hole that is also molded by the above-described extrusion press molding method by molding the shaft-shaped material with a spiral hole.

  In drilling with a drill, it is desirable to supply coolant such as coolant toward the tip of the cutting edge in order to cool and lubricate the machined part and discharge chips from the machined hole. In order to supply cutting fluid directly and efficiently, and to reliably discharge chips from the bottom of the hole with the supplied cutting fluid, the cutting fluid is supplied from the outside of the drill through the opening of the machining hole. Instead, it is more preferable to form a supply hole for the cutting fluid in the cutting edge part itself and supply it to the machining site from the vicinity of the cutting edge at the tip of the cutting edge part through the inside. However, in a so-called twist drill or the like in which a chip discharge groove that is twisted around its central axis is formed on the outer periphery of the cutting edge portion, in order to ensure the rigidity and strength of the cutting edge portion as the outer diameter of the cutting edge becomes smaller. In addition, the feed hole is also twisted around the central axis at the same twist angle as the chip discharge groove so that the supply hole is located between the chip discharge grooves in the circumferential direction in any cross section orthogonal to the center axis. Must be formed.

Therefore, in order to manufacture a drill in which a spiral hole for supplying a cutting fluid to the cutting edge is formed in this way, in Patent Documents 1 to 4, a plasticizer or the like is added to a raw material for a drill such as cemented carbide. When a shaft-shaped body manufactured by such a drill is formed by extruding and pressing the press raw material from the opening of the mold, pins and threads are provided in the mold, and the supply hole and And a method of forming a spiral hole therein by twisting a shaft-like body together with the hole. Therefore, after manufacturing the shaft-shaped material with a spiral hole that becomes the material of the drill by sintering or the like from the shaft-shaped body with the spiral hole formed in this way, the spiral hole in the circumferential direction is formed on the outer periphery of the portion that becomes the cutting edge portion of the drill. A drill in which a spiral hole that is twisted around the central axis of the cutting edge portion is formed at the same twist angle as the above-mentioned chip discharge groove by forming a helical chip discharge groove so as to be positioned in between Can be manufactured.
JP-A-62-228312 Japanese Patent Laid-Open No. 62-240701 JP-A-4-272108 Japanese National Patent Publication No. 6-508301

  By the way, for example, in a very small drill with a cutting blade outer diameter of 0.5 to 3.0 mm, the diameter of the shank for attaching it to the rotating shaft of the machine tool is the same as this cutting blade outer diameter or this cutting blade. Since the shaft-shaped material with a spiral hole is given an outer diameter larger than the outer diameter of the cutting blade in consideration of the grinding allowance, the outer diameter of the cutting blade portion is larger than the outer diameter. The chip discharge groove must be formed after cutting the material from the outer diameter to the cutting edge outer diameter. Therefore, even in the above-described shaft-shaped body with a spiral hole manufactured in such a shaft-shaped material with a spiral hole, the outer diameter, that is, the inner diameter of the opening of the mold is the twisted diameter of the spiral hole, that is, extrusion press molding. The amount of eccentricity of the pin or thread from the twisted center line of the twisted shaft, the difference between the outer diameter of the cutting edge and the shank diameter, the grinding allowance, or the sintering from the shaft to the material In consideration of the contraction allowance, etc., it is set large to some extent.

  On the other hand, the cutting performance of the chip is improved, and the chip is guided to the chip discharge groove together with the above-mentioned cutting fluid by rotation of the drill, so that the chip can be smoothly and smoothly fed from the rear end side of the cutting edge, that is, from the opening side of the machining hole. In order to discharge, it is desirable that a certain large twist angle is given to the chip discharge groove, and when the twist angle of the chip discharge groove is increased in this way, the chip discharge groove is also inserted into the spiral hole accordingly. A large torsion angle equal to the torsion angle must be given. The same applies to the small-diameter drill. Therefore, in that case, also in the shaft-shaped material and shaft-shaped body manufactured in this drill, the twist angle of the spiral hole is set to a large angle equivalent to the twist angle of the chip discharge groove.

  However, in particular, in the shaft-shaped body manufactured for the small-diameter drill, the outer diameter is set larger than the twist diameter of the spiral hole in the shaft-shaped body as described above. In order to increase the torsion angle of the shaft member, the outer periphery of the shaft member must be twisted at a larger angle than the twist angle of the spiral hole when the shaft member is extruded and press-molded. That is, the outer periphery of the shaft-like body and the spiral hole on the inner peripheral side follow the twist while twisting around the center line even though the diameter from the center line of the twist is different. Thus, the distance traveled in the direction of the center line, that is, the lead length is equal to each other, so that the twist angle on the outer periphery of the shaft-like body is larger than the twist angle of the spiral hole.

  However, in Patent Documents 1 to 4, first, in Patent Document 3, a spiral groove is formed on the inner periphery of the mold, and at the same time the shaft-like body is pushed out, the shaft-like body is formed along this groove. In such an extrusion press molding method, in order to increase the twist angle of the shaft-like body, the twist angle of the spiral groove on the inner periphery of the mold must be set to a large angle equal to this. In addition, it is difficult to manufacture a mold having such a strong twisted spiral groove, and a large pressing pressure is required to extrude the press raw material formed into the shaft-like body. Will be forced. In addition, since the extruded shaft-like body has a large resistance during twisting, it is difficult to twist so that the desired twist angle is given by reliably following the twist of the spiral groove. The accuracy of the length is impaired, and there is a possibility that it becomes impossible to form a chip discharge groove that can ensure smooth chip discharge as described above when manufactured into a drill.

  On the other hand, in Patent Document 1, the shaft-like body is first pushed straight without being twisted, and a straight hole is formed in the shaft-like body. The shaft-like body is twisted by a torsion roller so that the straight hole is formed. In addition, in Patent Document 2, the shaft-like body is pushed out in a rotating state by a rotating nozzle having a pin inside, and a straight hole is formed in the inside. When the end of the shaft-shaped body in the state comes into contact with the receiving surface and enters a non-rotating state, the shaft-shaped body is twisted, and this straight hole is also converted into a spiral hole. However, if the shaft-like body is strongly twisted with a large twist angle as described above to convert a straight hole into a twisted hole as described above, the press-formed shaft-like body is likely to be cracked or crushed. In Document 1, slip occurs between the shaft and the torsion roller, and in Patent Document 2 between the end of the shaft and the receiving surface that should be in a non-rotating state. Results in damage.

  Further, in Patent Document 4, a support for supporting the filamentous material is disposed inside the extrusion nozzle, and the nozzle base is formed in a smooth cylindrical shape, and at least one of the support and the nozzle base is rotated. It is described that it is possible. However, among these, when rotating the support body, it is inevitable that the drive device for rotationally driving the support body located near the opening in the mold is inevitable. Since the spiral hole is formed by twisting of the filamentous material following the rotation of the body, there is a possibility that sufficient lead length accuracy cannot be obtained. Further, when rotating the nozzle base, as described in Patent Document 4, surface friction is generated between the press raw material and the smooth nozzle base by a high extrusion pressure, and the friction force is applied to the surface. Since the extruded shaft-like body is twisted by the rotation of the die, twisting the shaft-like body with a strong twist as described above requires a larger extrusion press pressure, increasing the load on the device. On the other hand, if the pressing pressure is suppressed, a sufficient frictional force cannot be obtained and a slip occurs between the shaft-like body and the die, and it is impossible to give an accurate lead length accuracy to the spiral hole.

  The present invention has been made under such a background. In particular, in order to produce a small-diameter spiral hole drill as described above, a shaft having a spiral hole is extruded and press-molded. Provided is an extrusion press forming method of a shaft-shaped body with a spiral hole, which can reliably form a shaft-shaped body with a spiral hole with high lead length accuracy without requiring a high press pressure, and further this extrusion press Providing a shaft-shaped material with a spiral hole suitable as a material for the small-diameter spiral hole drill manufactured based on a molding method, and a small-diameter drill with a spiral hole in which a chip discharge groove is formed on the outer periphery of the cutting edge It is an object.

  In order to solve the above-described problems and achieve such an object, the method for extruding and pressing a shaft-shaped body with a spiral hole according to the present invention includes pressing and pressing a raw material from an inner peripheral portion of a cylindrical mold. An extrusion press molding method of a shaft-shaped body with a spiral hole for molding a shaft-shaped body having a spiral hole formed therein, wherein the mold has a position eccentric from the center line of the inner peripheral portion of the mold In addition, a linear body for forming the spiral hole is provided, a groove extending in the center line direction is formed on the inner peripheral surface of the mold, and the press raw material is rotated while rotating the mold around the center line. The shaft-shaped body is formed by extrusion.

  Further, the shaft-shaped material with spiral holes of the present invention is a shaft-shaped material with spiral holes manufactured from a shaft-shaped body with spiral holes formed by such an extrusion press molding method, and has an outer diameter of 4.0 mm. A spiral hole that twists around the central axis is formed on the inner peripheral side of the virtual cylindrical surface with a diameter of 3.0 mm centered on the central axis of the material main body in the material main body having a roughly cylindrical shape of about 5.0 mm. In addition, a spiral lead index that is twisted at a twist angle of 40 ° to 80 ° around the central axis in the same direction as the spiral hole is formed on the outer periphery of the material body. Furthermore, the small-diameter drill with a spiral hole of the present invention is a small-diameter drill with a spiral hole manufactured from a shaft-shaped body with a spiral hole formed by the extrusion press molding method as described above, and has an outer diameter of 0.5 mm to A 3.0mm cutting edge is formed A substantially cylindrical cutting edge portion is provided, and a chip discharge groove that is twisted at a twist angle of 15 ° to 40 ° around the central axis of the cutting edge portion is formed on the outer periphery of the cutting edge portion. In addition, a spiral hole that is twisted in the same direction as the chip discharge groove is formed in the cutting blade portion between the chip discharge grooves in the circumferential direction.

  In the extrusion press molding method having the above-described configuration, the press raw material is extruded inside the mold along the groove formed in the inner peripheral surface of the mold and extending in the center line direction, and the mold itself is rotated around the center line. Therefore, the molded shaft-like body is given a torsion of the lead length based on the rotational speed of the mold and the torsion angle with respect to the center line of the groove formed on the inner peripheral surface thereof. Therefore, even if the torsion to be applied to the shaft-like body is a strong torsion with a large torsion angle, the insufficient torsion amount is compensated by rotation of the mold without increasing the torsion angle of the groove with respect to the center line of the mold. Therefore, the mold can be easily manufactured, and a large pressing pressure is not required for extrusion, and the load on the apparatus can be reduced. Further, the shaft-like body pushed out through the mold is twisted while being retained while being guided by engaging with the groove, so that slip or cracking or crushing occurs between the inner peripheral surface of the mold. In combination with the fact that the twist angle of the groove can be reduced, the shaft body can be twisted by reliably following the groove, so that even if it is a strong twist, the lead length accuracy It is possible to form a shaft-like body having a high spiral hole.

  Therefore, in the shaft-shaped material with a spiral hole of the present invention manufactured by sintering or the like from the shaft-shaped body thus extrusion-molded, the outer diameter is approximately 4.0 mm to 5.0 mm as described above. A spiral hole that is twisted around the central axis is formed on the inner peripheral side of a virtual cylindrical surface having a diameter of 3.0 mm centered on the central axis of the material main body in the cylindrical material main body. Even if the twist angle of the hole is a relatively large angle of about 15 ° to 40 °, the lead length equal to the spiral hole in the same direction as the spiral hole around the central axis of the outer periphery of the material body Thus, it is possible to form such a spiral hole reliably and with high lead length accuracy in a state of being twisted with a large twist angle of about 40 ° to 80 °. The torsion angle of the outer periphery of the material main body is set such that, for example, an index providing means is fixedly provided outside the opening of the mold, and the outer periphery of the shaft-like body pushed out while rotating is fired in accordance with the lead length. It is possible to know by applying a spiral lead index such as a spiral groove remaining after ligation by the index providing means.

  Further, in the small-diameter drill with a spiral hole of the present invention, which is also obtained from the shaft-like body obtained by molding the shaft-like material into a predetermined size and shape, the outer diameter of the cutting blade is It has a small diameter of 0.5 mm to 3.0 mm, and a helical chip discharge groove is formed on the outer periphery of the cutting blade part, and the same as the chip discharge groove between the chip discharge grooves in the circumferential direction in the cutting blade part. Even if a spiral hole that twists in the direction is formed, or even if a shank part having a diameter larger than the outer diameter of the cutting edge is formed on the rear end side of the cutting edge part, the above-mentioned chips can be obtained without interfering with the spiral hole. The twist angle of the discharge groove can be set to a relatively large angle of 15 ° to 40 ° as described above. Therefore, according to such a small-diameter drill with a spiral hole, even if the outer diameter of the cutting edge is small as described above, the cutting edge can be passed through the spiral hole in the cutting edge without impairing the rigidity and strength of the cutting edge. While cutting fluid is supplied from the vicinity to the machining site at the bottom of the machining hole to ensure reliable cooling and lubrication, smooth and good chip discharge can be ensured. It is possible to perform small-diameter drilling of a printed board or the like that has not been performed with a single cut, and the processing efficiency can be significantly improved.

  In addition, in the extrusion press molding method of the shaft-shaped body with a spiral hole of the present invention, the groove formed on the inner peripheral surface of the mold may extend toward the center line direction of the inner peripheral portion of the mold, If the twist angle with respect to the center line is too large, the above-mentioned effects may not be sufficiently achieved, such as difficulty in mold manufacture, and it is not necessary to rotate the mold depending on the amount of twist applied to the shaft. End up. For this reason, it is desirable that the twist angle of this groove with respect to the center line of the mold be 40 ° or less. The groove may be a spiral groove that is twisted around the center line. However, in the present invention, the mold itself rotates to impart a twist to the shaft-like body, and depending on the magnitude of the twist. The groove may be a straight groove parallel to the center line.

  Further, the torsion lead length given to the shaft-like body is determined by the pressing speed (extrusion speed) of the shaft-like body pushed out from the inner periphery of the mold, the twist angle of the groove formed on the inner peripheral surface of the mold, and It is determined by the rotational speed around the center line of the rotating mold. Of these, the twist angle of the groove is constant at the time of extrusion press molding, and therefore the extrusion pressing is performed by controlling the rotational speed around the center line of the mold based on the pressing speed of the shaft-like body extruded from the mold. The lead length of the spiral hole of the shaft-like body can be maintained stably and with high accuracy. Therefore, even in the above-mentioned shaft-shaped material and small-diameter drill manufactured from such a shaft-like body, a spiral hole with higher lead length accuracy can be provided. It becomes possible to form reliably.

  FIG. 1 shows an extrusion press molding apparatus according to an embodiment of the extrusion press molding method for a shaft-shaped body with a spiral hole according to the present invention. In this molding apparatus, the mold 1 has a substantially cylindrical shape, and its inner peripheral portion 1A has a circular shape with a substantially constant cross section centered on the center line O of the cylinder formed by the mold 1, provided that its inner peripheral surface 1B. A groove 1C extending in the direction of the center line O is formed over the entire length of the inner peripheral portion 1A. Here, in the molding apparatus according to this embodiment, the groove 1C is a spiral groove that is twisted at a constant twist angle α around the center line O as shown in the figure, and has the same twist angle α. A plurality of grooves 1C are formed on the inner peripheral surface 1B at equal intervals in the circumferential direction. The twist angle α is set to 40 ° or less. Further, a disc-shaped flange portion 1D centering on the center line O is formed on the outer peripheral portion of the rear end side (left side in FIG. 1) of the mold 1.

  Such a mold 1 is attached to a front end portion of an extrusion cylinder 2 that supplies a press raw material to the inner peripheral portion 1A. The extrusion cylinder 2 includes a cylinder main body 3 formed so that a hole 3A having a diameter larger than the inner diameter of the inner peripheral portion 1A of the mold 1 is coaxial with the center line O, and a tip of the cylinder main body 3. A nozzle 4 having a concave conical diameter-reduced portion 4A which is attached and gradually decreases in diameter from the large-diameter hole portion 3A to the inner diameter of the inner peripheral portion 1A, and the nozzle 4 It is comprised from the cap 5 attached to the front end side. A screw 6 that is rotationally driven around a center line O by a rotational driving means (not shown) is inserted into the hole 3A of the cylinder body 3, and the press raw material is removed from the hole 3A by the rotation of the screw 6. It is supplied into the inner peripheral portion 1 </ b> A of the mold 1 through the hole 4 </ b> B of the nozzle 4.

  Here, the cap 5 has a multi-stage cylindrical shape whose inner and outer circumferences are reduced by one step toward the tip side, and the inner diameter of the tip side inner circumference part is a mold on the tip side from the flange part 1D. 1 is set to a size that allows the outer peripheral portion to be inserted, and an inner diameter of the rear end side inner peripheral portion is set to a size that allows the outer peripheral portion of the flange portion 1D to be inserted. And after making this mold 1 closely contact | adhere to the front-end | tip of the nozzle 4 so that the inner peripheral part 1A may connect with the said hole part 4B, as mentioned above, the front-rear end side inner peripheral part of the cap 5 The mold 1 is restrained from moving in the direction of the centerline O by fitting the cap 5 on the mold 1 from the front end side and attaching it to the nozzle 4 while fitting the outer peripheral portion of the front end side and the outer peripheral portion of the flange portion 1D. Thus, it is held at the tip of the push-out cylinder 2 so as to be rotatable around the center line O.

  An annular gear 7 centering on the center line O having a tooth surface 7A on the outer periphery is provided on the outer peripheral portion protruding from the cap 5 of the mold 1 held at the distal end portion of the extrusion cylinder 2 in this way. It is fitted and detachably attached. On the other hand, a rotation driving means 8 such as a motor is provided on the side of the extrusion cylinder 2 so that its rotation shaft 8A is parallel to the center line O and protrudes to the tip side. A gear 9 having a tooth surface 9A is also attached to the outer periphery, and these gears 7, 9 are connected by a belt 10 having a tooth surface 10A meshing with the tooth surfaces 7A, 9A formed on the inner periphery. . Therefore, by rotating the gear 9 by the rotation driving means 8, the gear 7 and the mold 1 are integrally rotated around the center line O via the belt 10. In the molding apparatus according to this embodiment in which the groove 1C formed on the inner peripheral surface 1B of the mold 1 is a spiral groove, the rotation direction of the mold 1 by the rotation driving means 8 is an axial shape as described below. The groove 1C is made to coincide with the direction in which the groove 1C is twisted toward the front end side in the center line O direction where the body A is pushed out.

  On the other hand, from the inside of the hole 4B of the nozzle 4 in the extrusion cylinder 2 to the inner peripheral portion 1A of the mold 1, there is a linear body 11 for forming the spiral hole B inside the shaft-like body A to be subjected to extrusion press molding. Is provided. The linear body 11 is formed of a flexible material that can follow the twist of, for example, a nylon thread or a Cu fine wire, and one end of the linear body 11 is passed through the hole 4B. While being joined to a position eccentric from the line O, the other end is a free end and extends to the vicinity of the opening on the front end side of the inner peripheral portion 1A of the mold 1. Further, in the molding apparatus according to the present embodiment, a pair of such linear bodies 11 are provided symmetrically with respect to the axis O.

  Further, on the side of the extrusion cylinder 2 on the tip side of the mold 1, a measuring means 12 that measures the pressing speed (extrusion speed) of the shaft-like body A that is pressed and extruded from the opening on the tip side of the inner peripheral portion 1 </ b> A of the mold 1. Is provided. This measuring means 12 is a non-contact type such as a laser Doppler sensor, for example, and is connected to a rotational driving means 8 such as the motor via a speedometer 13, a calculating means 14, a driver 15 and the like. Based on the pressing speed of the shaft A measured by the measuring means 12, the rotational speed around the center line O of the mold 1 by the rotational driving means 8 is controlled.

  Furthermore, on the outer side of the tip of the opening of the mold 1, an index applying means for applying a spiral lead index C that remains after sintering to the outer periphery of the shaft A that is pushed out while being rotated in accordance with the lead length. 16 is fixedly provided. The index applying means 16 is, for example, a marking needle that forms a shallow groove as the lead index C on the outer periphery of the shaft-like body A, and the tip of the fixed marking needle bites into the outer periphery of the shaft-like body A shallowly. When the shaft-like body A is pushed out while rotating, a spiral groove having a lead length equal to the lead length of the twist is provided as the lead index C on the outer periphery of the shaft-like body A as shown in FIG. Therefore, the lead index C is formed so as to form a twist angle β larger than the twist angle α formed by the groove 1C on the inner peripheral surface of the mold 1.

  In the extrusion press molding method of the shaft A with the spiral hole B of this embodiment using such a molding apparatus, for example, an appropriate plasticizer is added to and mixed with the raw material powder of a hard tool material such as cemented carbide. The press raw material is supplied from the hole 3A to the inner peripheral portion 1A of the mold 1 through the hole 4B by the screw 6 as described above, and is extruded from the opening on the front end side of the inner peripheral portion 1A while applying press pressure. Thus, the shaft A is formed. Therefore, the extruded shaft-like body A is formed into a substantially cylindrical shape with the center line O as the center. Further, at this time, the shaft-like body A is pushed out without being filled with the press raw material in the portion where the linear body 11 extends in the inner peripheral portion 1A of the mold 1, so that the trace is the shaft-like body A. Is left in the shaft-like body A as a hole extending in the direction of pushing out, that is, in the direction of the center line O.

  Then, the shaft-like body A is guided by the groove 1C formed on the inner peripheral surface 1B of the mold 1 during the extrusion press molding by the mold 1, and in this embodiment, along the spiral formed by the groove 1C. Twist is given around the center line O, and twist is also given in this rotational direction by rotating the mold 1 itself around the center line O by the rotation driving means 8. Incidentally, on the outer periphery of the shaft-like body A thus extruded, the same number of protrusions made of the press raw material that have entered the groove 1C as the grooves 1C formed on the inner peripheral surface 1B of the mold 1 are twisted. Although it is formed so as to be helically twisted at an angle equal to the angle α, illustration is omitted.

  The flexible linear body 11 extending from the hole 4B on the side of the extrusion cylinder 2 to the inner peripheral portion 1A of the mold 1 by twisting the shaft-shaped body A around the center line O in the mold 1 in this way, By following the twist of the shaft-like body A, the spirally twisted state is stabilized, so that the hole formed in the shaft-like body A is given to the shaft-like body A in the same manner as the lead index C. A spiral hole B that is twisted in the same direction as the lead index C with a lead length equal to the twisted lead length, that is, a lead length equal to the lead index C, is formed. In the molding apparatus according to the present embodiment in which the pair of linear bodies 11 are provided symmetrically with respect to the center line O, these linear bodies 11 have a double spiral shape in the inner peripheral portion 1A of the mold 1, Accordingly, the spiral holes B formed in the shaft-like body A are also double spiral holes B that are symmetrical with respect to the center line O with the same twist angle and lead length.

  FIG. 2 shows an embodiment of a shaft-shaped material with a spiral hole of the present invention produced from the shaft-shaped body A by sintering the shaft-shaped body A thus formed. That is, the shaft-shaped material of this embodiment is obtained by cutting and sintering the shaft-shaped body A extruded from the mold 1 by the above-described extrusion press molding method into a predetermined length, When the press raw material is a cemented carbide, it has a substantially cylindrical shape contracted by sintering, about 24% in the radial direction and about 22% in the length direction with respect to the cut shaft A. A spiral hole 22 that is twisted around a central axis X of a cylinder formed by the material main body 21 is formed inside the material main body 21 by a spiral hole B formed in the shaft-like body A. On the outer periphery of 21, a spiral groove 23 that is twisted with the same lead length in the same direction as the spiral hole 22 by the lead index C left on the outer periphery of the shaft-like body A is a shaft-shaped material with a spiral hole of this embodiment. It will be formed as a lead index.

  3 and 4 show an embodiment of a small-diameter drill with a spiral hole according to the present invention which is also produced from the shaft-like body A by further forming the shaft-like material of this embodiment. . That is, this small-diameter drill is centered on the central axis X common to the shaft-shaped material 21 by grinding the outer periphery of the shaft-shaped material 21 together with the spiral groove 23 on the rear end side of the drill body 31. A substantially cylindrical shank 32 is formed, and the tip side (left side in FIG. 3) of the shank 32 is further ground through a taper portion 33 that gradually decreases in diameter toward the tip side. A substantially cylindrical cutting edge 34 having a smaller diameter than the shank 32 is a so-called lumer drill that is integrally formed so as to extend along the central axis X.

  Further, on the outer periphery of the cutting edge portion 34, the drill body 31 opens in the tip flank 35 at the front end of the cutting edge portion 34 and moves toward the rear end side. A chip discharge groove 36 is formed, and a cutting edge 37 is formed at a cross ridge line portion between the wall surface facing the rotation direction T of the chip discharge groove 36 and the tip flank 35, and the chip discharge groove 36 is connected to the rear end side of the cutting edge 37. Then, the spiral hole 22 formed in the shaft-shaped material is left as it is in the drill body 31, so that the spiral hole 38 that twists around the central axis X from the rear end of the shank 32 toward the front end side. The spiral hole 38 extends so that the portion between the chip discharge grooves 36 in the circumferential direction in the cutting edge portion 34 is twisted in the same direction as the chip discharge grooves 36, and It is opened near the cutting edge 37.

  Here, in the drill of this embodiment having a small diameter, the outer diameter D of the cutting blade 37 is in the range of 0.5 mm to 3.0 mm, and this outer diameter D is the maximum outer diameter of the cutting blade portion 34. Therefore, the spiral hole 38 is at least in the range inside the outer diameter D, that is, the virtual cylindrical surface P whose maximum diameter around the central axis X is equal to 3.0 mm which is the maximum value of the outer diameter D. It is formed so as to extend spirally around the central axis X within the range of the inner peripheral side. The outer periphery of the cutting edge portion 34 may be provided with a back taper that gradually decreases in outer diameter from the position of the cutting edge 37 having the maximum outer diameter toward the rear end side. An undercut having a smaller outer diameter on the rear end side than the position may be formed. On the other hand, the outer diameter of the shank 32 is determined by the minimum gripping diameter that can be gripped by the spindle of the machine tool that grips the shank 32, and is generally set to 3.0 mm. Therefore, when the outer diameter D of the cutting edge 37 is 3.0 mm, which is the maximum in the above range, the cutting edge portion 34 also extends to the distal end side with the same diameter as the shank 32 and continues to the cutting edge 37.

  Further, since the spiral hole 38 is twisted in the same direction so as to extend in the circumferential direction between the chip discharge grooves 36 in the cutting edge portion 34, the spiral hole 38 and the chip discharge groove 36 have a central axis line. The twist angles γ of the chip discharge grooves 36 are set to 15 ° to 40 °. However, since the twist angle γ of the chip discharge groove 36 is the twist angle at the outer periphery of the cutting blade portion 34, the spiral hole 38 is formed inside the cutting blade portion 34. As for the twist between the screw hole 38 and the spiral hole 38, the twist angle is strictly equal to the twist angle γ of the chip discharge groove 36 slightly larger than the twist angle of the spiral hole 38.

  Therefore, also in the shaft-shaped material with a spiral hole of the above-described embodiment formed into such a small-diameter drill by grinding, the spiral hole 22 extending into the material body 21 has a diameter from the central axis X of the material body 21. It is formed so as to be helically twisted in a range on the inner peripheral side from the virtual cylindrical surface P equal to the maximum value of the outer diameter D, that is, inside the virtual cylindrical surface P having a maximum diameter of 3.0 mm. On the other hand, the outer diameter E of the material body 21 is set to 4.0 mm to 5.0 mm in consideration of the outer diameter of the shank 32 and the grinding allowance, and the outer circumference of the material body 21 has a lead length equal to that of the spiral hole 22. The spiral groove 23 formed in the above has a twist angle δ with respect to the central axis X in the range of 40 ° to 80 °. In this embodiment, since the spiral hole B formed in the shaft-shaped body A is a double helix symmetric with respect to the center line O as described above, in the shaft-shaped material manufactured from this shaft-shaped body A The spiral hole 22 and the spiral hole 38 in the small-diameter drill are also double spirals symmetrical about the central axis X. Therefore, this small-diameter drill is a so-called two-blade twist drill in which a pair of cutting edges 37 and a spiral chip discharge groove 36 are formed symmetrically with respect to the central axis X in the cutting edge portion 34.

  However, in the small-diameter drill with a spiral hole configured as described above, the outer diameter D of the cutting blade 37 at the tip of the cutting blade portion 34 is as small as 0.5 mm to 3.0 mm, whereas the cutting blade portion 32. On the rear end side, a shank 32 having a larger diameter or the same diameter is integrally formed, and a spiral hole 38 is formed in the drill body 31 from the shank 32 to the cutting edge 34 to directly apply the cutting oil. Even when an attempt is made to supply the processed portion by the cutting edge 37, the twist angle γ of the chip discharge groove 36 formed spirally on the outer periphery of the cutting edge portion 34 with the spiral hole 38 interposed in the circumferential direction is 15 Since this type of small-diameter drill has a relatively large angle of from 40 ° to 40 °, the cutting performance of the chips generated by the cutting blade 37 is improved, and the cutting edge portion 34 is smoothly and reliably provided. Lead to the end side and eject from the processing hole It can be. Therefore, for example, in drilling a printed circuit board with such a small-diameter drill, it has been necessary to perform step processing in which the drill body is fed stepwise while moving the drill body forward and backward. Dawning can be performed, and the processing efficiency can be greatly improved.

  Further, since the twist angle γ of the chip discharge groove 36 is a large angle as described above, the intersecting ridge line between the wall surface facing the rotation direction T of the chip discharge groove 36 and the tip flank 35 of the cutting edge portion 34. The rake angle of the cutting edge 37 formed in the portion can be set to be large, thereby improving the sharpness of the cutting edge 37 and reducing the resistance. Of course, since the spiral hole 38 is formed in the part between the chip discharge grooves 36 in the circumferential direction having a large wall thickness in the cutting edge part 34, it is sufficient without impairing the rigidity and strength of the cutting edge part 34. A spiral hole 38 having a size can be formed, and the cutting fluid can be directly supplied from the tip flank 35 in the vicinity of the cutting blade 37 to the processing site through the spiral hole 38. The blade 37 can be reliably cooled and lubricated, and a smoother and better chip discharging property can be obtained.

  If the outer diameter D of the cutting edge 37 is smaller than the above range, the absolute rigidity and strength of the cutting edge portion 34 cannot be ensured and the drill body 31 may be broken. When the outer diameter D is larger than the above range, it is not suitable for drilling such as a printed circuit board as described above. On the other hand, if the twist angle γ of the chip discharge groove 36 is smaller than the above range, the chip breaking property is poor, so that smooth discharge of the chip passing through the chip discharge groove 36 may be hindered or chip clogging may occur. On the other hand, even if the twist angle γ is larger than the above range, the entire length of the chip discharge groove 36 becomes long, so that the chip discharge performance may be impaired.

  On the other hand, in the shaft-shaped material with a spiral hole having the above-described configuration, a virtual diameter of 3.0 mm at maximum with the central axis X in the material body 21 having a substantially cylindrical shape having an outer diameter E of 4.0 mm to 5.0 mm as the center. A spiral hole 22 serving as a spiral hole 38 that is twisted at a twist angle substantially equal to the twist angle γ of the chip discharge groove 36 is formed on the inner peripheral side of the cylindrical surface P, that is, in the cutting blade portion 34 of the small-diameter drill. The spiral groove 23 having a twist angle δ with respect to the central axis X of 40 ° to 80 ° is formed on the outer periphery of the material main body 21 so as to have a lead length equal to that of the spiral hole 22. By grinding the shaft-shaped material, it is possible to reliably form the small-diameter drill with a spiral hole as described above. That is, when the twist angle δ of the spiral groove 23 is out of the above range, the twist angle of the spiral hole 22 also changes. Therefore, the twist angle γ of the chip discharge groove 36 between the spiral holes 38 in the small diameter drill is set to the above range. You may not be able to do it. On the other hand, if the outer diameter E of the material body 21 is larger than the above range, the grinding allowance for forming a small-diameter drill by grinding becomes too large and the yield from the raw material to the product deteriorates, while the outer diameter E is too small. Then, there is a possibility that the outer diameter of the shank 32 that can be gripped by the main spindle of the general machine tool as described above cannot be secured.

  And in the extrusion press molding method of the said structure which shape | molds the shaft-shaped body A with a spiral hole manufactured to such a shaft-shaped raw material with a spiral hole and a small diameter drill with a spiral hole, the mold which shape | molds this shaft-shaped body A A groove 1C extending in the direction of the center line O of the inner peripheral portion 1A of the mold 1 is formed on the inner peripheral surface 1B of the mold 1, and the shaft-like body A is extruded so as to be guided along the groove 1C. Since the mold 1 itself is also rotated around the center line O by the rotation driving means 8, it is given to the shaft-like body A in order to form a spiral hole B that becomes the spiral holes 22 and 38 of the shaft-shaped material and the small-diameter drill. The twist is obtained by adding the twist due to the rotation of the mold 1 to the twist with respect to the center line O of the groove 1C. That is, even if the twist of the groove 1C is insufficient, even if the twist applied to the shaft A is insufficient, this shortage can be compensated by the twist caused by the rotation of the mold 1. In other words, the twist angle α of the groove 1C is reduced. However, it is possible to impart a desired twist to the shaft A by adjusting the rotational speed of the mold 1.

  Therefore, according to the extrusion press molding method having the above-described configuration, even when the shaft-like body A is subjected to strong torsion in order to produce the above-described shaft-shaped material with spiral holes or the small-diameter drill with spiral holes, the mold 1 The groove 1C formed in the inner peripheral surface 1B can be kept relatively small such that the twist angle α in the molding method of the present embodiment is 40 ° or less, for example. That is, the twist of the groove 1C itself becomes gentle and the length of the groove can be shortened, so that the mold 1 can be easily manufactured. In this way, the twist of the groove 1C becomes gentle so that the shaft-like body A is formed along the groove 1C. The press pressure required to supply and extrude the press raw material to the inner peripheral portion 1A of the mold 1 to twist can be reduced, and the load on the mold 1 and the extrusion cylinder 2 due to the press pressure and the press pressure can be reduced. It is possible to reduce the load on the molding apparatus, such as a load for driving the screw 6 to rotate.

  In addition, the shaft A in the inner peripheral portion 1A of the mold 1 is pressed in the circumferential direction by pressing the raw material into the groove 1C despite the mold 1 itself rotating. While being twisted around the center line O so as to engage with the groove 1C, it is pushed out in the direction of the center line O so as to be guided by the groove 1C. Therefore, even if the twist applied to the shaft-like body A is a strong twist, the shaft-like body A is pushed out while being retained by the groove 1C, so that it is cracked or crushed, and the inner peripheral surface 1B of the rotating mold 1 The shaft-shaped body A having a predetermined shape and size can be surely formed, and a spiral hole B with high lead length accuracy can be formed in the inside thereof. It becomes. For this reason, according to the extrusion press molding method, even when a shaft-shaped material with a spiral hole or a small-diameter drill with a spiral hole as described above is manufactured from the molded shaft-shaped body A, the material body 21 or the drill body 31 is used. The spiral holes 22 and 38 having a predetermined lead length can be accurately formed therein, and the chip discharge groove 36 on the outer periphery of the cutting edge 34 can be reliably formed at a large twist angle γ as described above, particularly in a small-diameter drill. can do.

  Here, the following table 1 shows the twist angle of the chip discharge groove 36 (however, the cutting edge when the outer diameter D of the cutting edge 37 of the small-diameter drill with a spiral hole is variously changed based on the embodiment described above. The torsional lead length of the shaft A with a spiral hole and the torsion angle β of the outer lead index C and the axial shape with a spiral hole when the torsion angle γ of the portion 34 is about 30 °. Relationship between the twist angle δ of the spiral groove 23 as a lead index on the outer periphery of the raw material body 21, the outer diameter D of the cutting blade 37 of the small-diameter drill with a spiral hole, the lead length of the chip discharge groove 36, and the twist angle γ. This is an example. However, in any example, the outer diameter of the shaft-shaped body A is 5.9 mm, the outer diameter E of the material body 21 in the shaft-shaped material is 4.5 mm, and the outer diameter of the shank 32 of the drill body 31 in the small-diameter drill is 3. Common at 0.0 mm. Further, the twist angle α of the groove 1C of the mold 1 is also common at 40 °, that is, the shaft A having different lead lengths and twist angles β is extruded by adjusting the rotation speed using the common mold 1 and press. Molded.

  As shown in Table 1, the shaft-like body A has a cutting edge 37 of a small-diameter drill such that the lead index C on the outer periphery has a twist angle β larger than the twist angle α of the groove 1C of the mold 1. As the outer diameter D becomes smaller, a stronger twist is given with a shorter lead length. Therefore, in the small-diameter drill with a spiral hole formed from a shaft-shaped material obtained by sintering such a shaft-shaped body A, as described above, a small diameter is provided on the distal end side of the large-diameter (3.0 mm) shank 32. Or even if the cutting edge portion 34 having the cutting edge 37 of the outer diameter D having the same diameter is integrally formed, the twist angle of the spiral hole 38 formed therein can be increased, Accordingly, a relatively large torsion angle γ of around 30 ° can be secured also in the chip discharge groove 36 on the outer periphery of the cutting edge portion 34, and efficient drilling can be performed due to excellent chip discharge performance. .

  Moreover, in the extrusion press molding method of the shaft-shaped body A with a spiral hole according to the present embodiment, the mold 1 is configured such that the gear 7 attached to the outer periphery of the mold 1 is connected to the gear 9 of the rotation driving means 8 by the belt 10. The rotation driving means 8 is capable of rotating the pressing speed of the shaft-like body A pushed out from the tip of the inner circumference 1A of the mold 1 by the measuring means 12. Measurement is performed and control is performed based on the measurement result. That is, when the press speed of the shaft A is increased, the rotation speed of the mold 1 by the rotation driving means 8 is also increased to compensate for the insufficient torsional rotation amount. Conversely, when the press speed is decreased, the rotation speed is increased. It is possible to prevent the shaft A from being twisted too much later.

  Therefore, for example, even if the supply speed of the press raw material supplied to the mold 1 changes due to, for example, a change in the rotational speed of the screw 6 or a change in the properties of the press raw material, the press speed also changes quickly. Thus, the rotational speed of the mold 1 by the rotation driving means 8 can be adjusted, and the shaft-like body A having the spiral hole B having a desired lead length can always be reliably formed. Even in a shaft-shaped material or a small-diameter drill manufactured from A, it is possible to reliably form the spiral holes 22 and 38 with higher lead length accuracy. Moreover, in the present embodiment, since the measuring means 12 is a non-contact type such as a laser Doppler sensor, the shaft-like body A is used for measuring the pressing speed as in the case of using the contact-type measuring means. There is no risk of deformation.

  In the present embodiment, the groove 1C formed on the inner peripheral surface 1B of the mold 1 has a spiral shape that twists around the center line O of the inner peripheral portion 1A of the mold 1 at a twist angle α. The rotational direction of the mold 1 is such that the spiral groove 1C is twisted toward the tip end side of the mold 1 from which the shaft-like body A is extruded. As described above, in the extrusion press molding method of the present invention, Since the shortage of the twist of the shaft A due to the groove 1C of the mold 1 can be compensated by the rotation of the mold 1, the twist angle α is 0 °, that is, the groove 1C extends parallel to the center line O of the mold 1. Even if the groove 1C itself is formed and the shaft-like body A is not twisted, it is possible to impart the necessary twist to the shaft-like body A only by the rotation of the mold 1. In this case, For mold 1 The can be more easily. Furthermore, in some cases, a twist larger than the twist imparted to the shaft-like body A by the groove 1C is imparted in a direction opposite to the direction in which the groove 1C is twisted toward the tip end side of the mold 1 from which the shaft-like body A is pushed out. Although it is possible to rotate the mold 1 as described above, in such a case, since the mold 1 must be rotated at a higher speed, it is formed in a spiral shape as in this embodiment. It is desirable that the twisting direction of the groove 1C matches the rotational direction of the mold 1.

It is sectional drawing which shows the extrusion press molding apparatus of the axial body A with a spiral hole concerning one Embodiment of the extrusion press molding method of the axial body with a spiral hole of this invention. It is a partially broken side view which shows one Embodiment of the shaft-shaped raw material with a spiral hole of this invention. It is a side view which shows one Embodiment of the small diameter drill with a spiral hole of this invention. It is a front view of the small diameter drill with a spiral hole of embodiment shown in FIG.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Mold 1A Inner peripheral part 1B Mold 1 Inner peripheral surface 1C Groove 2 Extrusion cylinder 6 Screw 7, 9 Gear 8 Rotation drive means 10 Belt 11 Linear body 12 Measuring means 14 Calculation means 21 Material body 22 Spiral hole 23 Spiral groove (lead index in shaft-shaped material with spiral hole)
31 Drill body 32 Shank 34 Cutting edge portion 36 Chip discharge groove 37 Cutting blade 38 Spiral hole A Spiral hole-shaped shaft B B Spiral hole C Lead index in spiral-shaped shaft-shaped body D Spiral hole 37 Outer diameter E Outer diameter of shaft material material 21 with spiral hole O Center line of inner periphery 1A of mold 1 and shaft body A with spiral hole X Material material 21 of shaft material with spiral hole and spiral hole Center axis of drill body 31 of small diameter drill α Torsion angle with respect to center line O of groove 1C in mold 1 Torsion angle with respect to center line O of lead index C in shaft body A with spiral hole γ Chip discharge in small diameter drill with spiral hole Twist angle with respect to the central axis X of the groove 36 δ Twist angle with respect to the central axis X of the spiral groove (lead index) 23 in the shaft-shaped material with spiral holes

Claims (5)

  A method of extruding and pressing a shaft-shaped body with a spiral hole by forming a shaft-shaped body having a spiral hole formed therein by extruding and pressing a press raw material from an inner peripheral portion of a cylindrical mold, Is provided with a linear body forming the screw hole at a position eccentric from the center line of the inner peripheral portion of the mold, and a groove extending in the center line direction is formed on the inner peripheral surface of the mold. A method for extruding and pressing a shaft-shaped body with spiral holes, wherein the shaft-shaped body is formed by extruding the press raw material while rotating the mold around the center line.   2. The method for extruding and pressing an axial body with a spiral hole according to claim 1, wherein the groove is a spiral groove parallel to the center line or having a twist angle of 40 degrees or less with respect to the center line. .   3. The spiral hole according to claim 1, wherein a rotational speed of the mold around the center line is controlled based on a pressing speed of the shaft-like body pushed out from an inner peripheral portion of the mold. Extrusion press molding method of shaft-like body.   A shaft-shaped material with a spiral hole manufactured from the shaft-shaped body with a spiral hole formed by the extrusion press molding method of the shaft-shaped body with a spiral hole according to any one of claims 1 to 3, wherein Is twisted around the central axis on the inner peripheral side of a virtual cylindrical surface with a diameter of 3.0 mm centered on the central axis of the material main body in the material main body having a substantially cylindrical shape of 4.0 to 5.0 mm A spiral hole index is formed on the outer periphery of the material body, and a spiral lead index that is twisted at a twist angle of 40 ° to 80 ° around the central axis in the same direction as the spiral hole. A shaft-shaped material with a spiral hole. A small-diameter drill with a spiral hole manufactured from a shaft-shaped body with a spiral hole formed by the extrusion press molding method of the shaft-shaped body with a spiral hole according to any one of claims 1 to 3, wherein the outer diameter is A substantially cylindrical cutting blade portion formed with a cutting blade of 0.5 to 3.0 mm is provided, and the outer periphery of the cutting blade portion is connected to the cutting blade and is around 15 to 40 around the central axis of the cutting blade portion. A chip discharge groove that is twisted at a twist angle of ° is formed, and a spiral hole that is twisted in the same direction as the chip discharge groove is formed in the cutting blade portion between the chip discharge grooves in the circumferential direction. A small diameter drill with a spiral hole.

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