JP2014193513A - Drill - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the increase of cutting resistance in a thinning edge while preventing damage or the like by securing a cutting edge strength in a connection part of the thinning edge and a main cutting edge.SOLUTION: A cutting edge 4 formed at the top of a drill body 1 rotated around an axis line O is provided with a main cutting edge 4A extending from an outer peripheral end to an inner peripheral side, and a thinning edge 4B. The thinning edge 4B is connected to the main cutting edge 4A through a connection part 4C which is formed in a projecting curve shape contacting the main cutting edge 4A or in a projectingly curved broken line shape comprising a plurality of straight lines in view of the top side of an axis line O direction. Further, horning is applied to at least the connection part 4C side of the main cutting edge 4A to form a horning face 7. The horning angle of the horning face 7 is equalized to the rake angle of the thinning edge 4B by the thinning face 6A and thereby, the horning face 7 smoothly continues to the thinning face 6A.

Description

  The present invention relates to a drill having a cutting blade in which a thinning blade connected to the inner periphery of a main cutting blade is formed.

  As a drill having such a thinning blade, for example, in Patent Document 1, a chisel edge that is continuous with a tip cutting edge ridge (main cutting edge) by a thinning on the flank side is formed at the tip of a drill body. A narrow chamfered portion is formed on the thinning side, and the tip cutting edge ridge has a connecting surface consisting of an arc surface or a plane on the thinning vertical surface constituting the chisel edge at the core thickness portion, Small arc ridges or small straight ridges are formed, and all ridge lines including these small arc ridges or small straight ridges have been subjected to honing processing that is continuous with the chamfered portion. Yes.

  Further, in Patent Document 2, a linear first cutting edge (main cutting edge) is formed by a tip flank and a chip discharge groove on the outer peripheral side of the tip of the drill body, and more central than the first cutting edge. A thinning surface is formed on the part side, and a second cutting edge (thinning blade) is formed by the thinning surface and the tip flank, and the first rake angle of the first cutting edge is reduced to reduce the first cutting edge. It has been proposed that a rake face of the chip discharge groove with respect to the blade is formed with a gash surface extending toward the outer periphery, and the gash face has a substantially triangular shape.

JP-A-4-25308 JP 2005-186247 A

  However, in the drill described in Patent Document 1, a chamfered portion is formed and honed on all ridge lines from the thinning side of the chisel edge to the tip cutting edge ridge including the small arc ridge or the small straight ridge. Therefore, although the cutting edge strength is improved, the cutting resistance is increased particularly on the thinning side, and the thrust load is increased in spite of the thinning.

  On the other hand, in the drill described in Patent Document 2, the gash surface has a triangular shape and is in contact with the thinning surface at one point, or a portion where the gash surface is not formed is formed between the thinning surface and becomes discontinuous. For this reason, particularly when both the first and second cutting edges are linear as described in Patent Document 2, this portion to which the first and second cutting edges are connected and the above-mentioned one point Therefore, there is a possibility that the cutting edge strength is impaired and a defect or the like is likely to occur. Such a problem occurs particularly when the cutting edge where the cutting edge is formed is made of an ultra-high pressure sintered body such as a diamond sintered body or a cBN (cubic boron nitride) sintered body. The bonded body is extremely hard, but becomes noticeable because it is brittle.

  The present invention has been made under such a background, and suppresses an increase in cutting resistance in the thinning blade while ensuring the cutting edge strength at the connection portion of the thinning blade with the main cutting edge to prevent chipping and the like. The aim is to provide a drill that can be.

  In order to solve the above problems and achieve such an object, according to the present invention, a chip discharge groove is formed on the outer periphery of the tip of the drill body rotated about the axis, and the drill rotation direction of the chip discharge groove is changed. A drill in which a cutting edge is formed at an intersecting ridge line portion between a facing wall surface and a tip flank of the drill body, the cutting edge including a main cutting edge extending from an outer peripheral end of the cutting edge to an inner peripheral side, The inner peripheral part of the wall surface facing the drill rotation direction of the chip discharge groove is formed at the intersecting ridge line part of the thinning surface facing the drill rotation direction of the thinning part formed so as to cut out on the axis side and the tip flank surface. A thinning blade connected to the inner periphery of the main cutting edge, and the thinning blade has a convex curved line shape or a bent line shape formed by a plurality of straight lines in contact with the main cutting edge when viewed from the axial front end side. Connected to the main cutting edge via the connection In addition, honing is performed on at least the connection portion side of the main cutting blade to form a honing surface, and the honing angle of the honing surface is equal to the rake angle of the thinning blade by the thinning surface. The honing surface and the thinning surface are smoothly continuous.

  Therefore, in the drill configured in this way, the thinning blade is mainly connected via a connecting portion having a convex curve shape or a curved line shape composed of a plurality of straight lines in contact with the main cutting blade as viewed from the axial front end side. Since it is connected to the cutting edge and honing is applied to the connecting part side of the main cutting edge, it is possible to ensure the cutting edge strength at the part where the connecting part of the thinning blade and the main cutting edge are connected. Defects can be prevented.

  The honing angle of the honing surface by this honing is equal to the rake angle of the thinning blade, and the honing surface and the thinning surface are smoothly continuous, that is, the honing surface of the honing applied to the main cutting edge and the thinning Even if the cutting edge is formed with a brittle ultra-high pressure sintered body such as a diamond sintered body or a cBN sintered body, the thinning surface connected to the blade connecting portion is not discontinuous. It is possible to reliably prevent defects and the like. On the other hand, since it is no longer necessary to honing the thinning blade while ensuring the strength of the cutting blade in this way, it is possible to reliably reduce the thrust load by suppressing an increase in the cutting resistance in the thinning blade. .

  Here, the radius of curvature of the convex curve formed by the connecting portion as viewed from the axial front end side or the radius of the circle inscribed in the convex bent line is 0.1 × D or more with respect to the outer diameter D of the cutting edge. It is desirable that If the radius of curvature of the convex curve or the radius of the circle inscribed in the convex bent line is smaller than 0.1 × D with respect to the outer diameter D of the cutting edge, the connection portion becomes close to a sharp corner, and the defect, etc. May not be sufficiently prevented.

  Further, in order to more surely prevent chipping or the like on the connecting portion side of the main cutting edge, a minute chamfer having a convex curved cross section is formed at the intersecting ridge line portion between the honing surface and the tip flank formed on the main cutting edge. Is desirable. The radius of curvature of the convex curve formed by the micro-chamfered cross-section is preferably about 0.01 mm to 0.02 mm (10 μm to 20 μm), for example.

  As described above, according to the present invention, even if the cutting edge portion is formed of an ultra-high pressure sintered body, the connection portion between the main cutting edge and the thinning blade or the cutting portion at the portion where the honing surface and the thinning surface are continuous. The strength of the blade can be secured to prevent chipping and the like, and an increase in cutting resistance in the thinning blade can be suppressed to reliably reduce the thrust load.

It is a side view of a drill main part tip part showing one embodiment of the present invention. It is the front view seen from the axial direction front end side which shows one cutting blade of the drill main body front-end | tip part shown in FIG. It is ZZ expanded sectional drawing in FIG.

  1 to 3 show an embodiment of the present invention. In this embodiment, the drill body 1 has an outer cylindrical shape centered on the axis O, and a rear end portion (not shown) is a shank portion. The shank portion is gripped by the main shaft of the machine tool, thereby rotating around the axis O. While being rotated in the drill rotation direction T, the workpiece is sent to the tip side in the axis O direction (upper side in FIG. 1) to drill a work material.

  The drill body 1 may be integrally formed of a hard material such as a cemented carbide, and the tip of the drill body 1 at which the cutting edge described later is formed is a diamond sintered body or It may be formed of an ultra-high pressure sintered body such as a cBN sintered body, and the other parts may be formed of a hard material such as a cemented carbide.

  On the outer periphery of the tip of the drill body 1, there is a chip discharge groove 2 that opens at the tip surface of the drill body 1 and twists toward the rear side in the drill rotation direction T around the axis O toward the rear end side. In the form, a pair is formed with rotational symmetry of 180 ° with respect to the axis O, the wall surface of the chip discharge groove 2 facing the drill rotation direction T, and the drill rotation direction from the opening of the chip discharge groove 2 on the tip end surface of the drill body 1. Cutting edges 4 are respectively formed at intersection ridges with the tip flank 3 extending to the T rear side. That is, the drill of this embodiment is a two-blade twist drill.

  The tip flank 3 inclines toward the rear end side of the drill body 1 toward the rear side of the drill rotation direction T, gives a clearance angle to the cutting edge 4, and moves toward the outer peripheral side of the tip portion of the drill body 1. Even if it is directed, the cutting edge 4 is inclined so as to be directed toward the rear end side, and a tip angle is given to the cutting edge 4. In this embodiment, the tip flank 3 is connected to the first flank 3A continuous to the rear side of the drill rotation direction T of the cutting edge 4 and further to the rear side of the first flank 3A in the drill rotation direction T. A second flank 3B having a larger flank angle than the first flank 3A is formed.

  Further, in the tip portion of the drill main body 1, coolant holes 5 that are twisted with leads equal to these chip discharge grooves 2 are formed at portions between the pair of chip discharge grooves 2 in the circumferential direction. In the present embodiment, these coolant holes 5 are opened to the second flank 3 </ b> B at the tip flank 3 of the drill body 1.

  Further, on the inner peripheral side of the opening in the tip end surface of the drill body 1 of the chip discharge groove 2, that is, on the axis O side, the inner peripheral part of the wall surface facing the drill rotation direction T of the chip discharge groove 2 is notched to the axis O side. Thus, a thinning portion 6 is formed. The thinning portion 6 includes a thinning surface 6A facing the drill rotation direction T and a thinning that faces the rear side of the drill rotation direction T and intersects the second flank 3B of the tip flank 3 adjacent to the drill rotation direction T side. A wall surface 6B is formed, and the thinning wall surface 6B extends to reach the outer periphery of the tip of the drill body 1 in this embodiment.

  The cutting edge 4 includes a main cutting edge 4A extending from the outer peripheral end of the cutting edge 4 to the inner peripheral side, and an inner periphery of the main cutting edge 4A. The thinning surface 6A of the thinning portion 6 and the tip flank 3 A thinning blade 4B formed at a crossing ridge line portion with (first flank 3A) is formed. The wall surface of the chip discharge groove 2 facing the drill rotation direction T is a rake face of the main cutting edge 4A, and the main cutting edge 4A is given a positive rake angle by twisting the chip discharge groove 2 as described above. In addition, the thinning surface 6A is a rake face of the thinning blade 4B.

  In the present embodiment, as shown in FIG. 2 when viewed from the front end side in the axis O direction, the main cutting edge 4A is formed so as to extend linearly, and the thinning blade 4B has a convex curve shape in contact with the main cutting edge 4A. Is connected to the main cutting edge 4A through the connecting portion 4C, and extends in the direction intersecting the obtuse angle from the connecting portion 4C to the main cutting edge 4A in a straight line shape and extends toward the axis O. Yes. The connecting portion 4C is an arc having a radius R, and such a connecting portion 4C is formed by making the main cutting edge 4A side of the thinning surface 6A into a cylindrical surface shape having the radius R.

  Furthermore, honing is performed on at least the connection portion 4C side of the main cutting edge 4A to form a honing surface 7, and in this embodiment, the honing surface 7 is formed over the entire length of the main cutting edge 4A. As shown in FIG. 3, this honing is performed by chamfer honing in which a cross ridge line portion between the rake face of the main cutting edge 4A having a positive rake angle and the tip flank 3 (first flank 3A) is chamfered in a straight section. The honing angle θ of the honing surface 7 is 0 ° or a negative angle, and is 0 ° in the present embodiment, that is, the honing surface 7 is parallel to the axis O.

  In addition, it is desirable that the width of the honing surface 7, that is, the honing width is in the range of 0.005 mm to 0.2 mm. Further, even if a minute chamfer forming a convex cross section (convex arc) having a radius of curvature of about 0.01 mm to 0.02 mm is formed on the intersecting ridgeline portion 4D of the honing surface 7 and the tip flank 3. When the minute chamfer is formed in this way, the width of the honing surface 7 is made larger than the curvature radius of the minute chamfer.

  The rake angle of the thinning surface 6A, which is the rake face of the thinning blade 4B, is made equal to the honing angle θ of the honing surface 7, whereby the honing surface 7 and the thinning surface 6A are smoothly continuous. Formed as follows. That is, in this embodiment, the rake angle of the thinning blade 4B is set to 0 °, and the thinning surface 6A also extends parallel to the axis O.

  In the drill having such a configuration, a convex curve (a convex arc having a radius R in the present embodiment) in contact with the main cutting edge 4A when viewed from the front end side in the axis O direction on the cutting edge 4 on the main cutting edge 4A side of the thinning blade 4B. 4C is formed so that the straight thinning blade and the main cutting edge do not cross each other directly, and the thinning blade 4B is connected to the main cutting edge 4A via this connection portion 4C. Therefore, the strength of the cutting edge 4 at the portion where the main cutting edge 4A and the thinning edge 4B are continuous can be ensured. Note that the same effect can be obtained even if the connecting portion 4C has a bent polygonal shape consisting of a plurality of extremely short straight lines when viewed from the front end side in the axis O direction.

  Furthermore, since the main cutting edge 4A is honed to form the honing surface 7, the cutting edge strength of the main cutting edge 4A can be ensured. The honing angle θ of the honing surface 7 and the rake angle of the thinning surface 6A, which is the rake face of the thinning blade 4B including the connecting portion 4C, are equal to each other, and the honing surface 7 and the thinning surface 6A are smooth. Therefore, the strength of the thinning blade 4B can be secured without impairing the sharpness of the thinning blade 4B by honing the thinning blade 4B separately.

  Therefore, according to the drill having the above-described configuration, the strength of the cutting edge 4 can be sufficiently ensured in the entire portion from the main cutting edge 4A to the thinning edge 4B on the inner peripheral side of the tip of the drill body 1 where a large thrust load acts. Even if the cutting edge 4 on which the cutting edge 4 is formed is ultra-high hardness, the cutting edge 4 is chipped or chipped even if it is formed of the above-described ultra-high pressure sintered body that is brittle and easily chipped. Can be prevented. Furthermore, since the sharpness of the thinning blade 4B can be maintained, the thrust load itself can be reduced by suppressing the cutting resistance from increasing.

  Here, the radius of curvature of the convex curve (in this embodiment, the radius R of the convex arc) formed by the connecting portion 4C when viewed from the front end side in the axis O direction is the outer diameter D of the cutting edge 4, that is, the outer peripheral end of the cutting edge 4. The diameter of the circle formed around the axis O is preferably 0.1 × D or more, and more preferably 0.2 × D or more. If the radius of curvature is smaller than 0.1 × D, the connecting portion 4C may be close to a sharp corner, and the connecting portion 4C may be easily damaged.

  The upper limit of the radius of curvature of the convex curve is desirably 0.5 × D. If the radius of curvature is larger than this, a connection is required to form the connecting portion 4C so as to contact the main cutting edge 4A. The part 4C may become too long. In addition, as above-mentioned, when the connection part 4C is formed in the broken line shape which curves by several short straight lines, what is necessary is just to let the radius of the circle | round | yen inscribed in these straight lines be the said curvature radius.

  Furthermore, by forming the fine chamfering having a convex cross-section as described above at the intersecting ridge line portion 4D between the honing surface 7 and the tip flank 3 of the main cutting edge 4A, it is possible to prevent the cutting edge 4 from being broken more reliably. can do. Such minute chamfering may be extended to the intersection ridge line portion between the thinning surface 6A of the thinning blade 4B including the connecting portion 4C and the tip flank 3, and in this case, it extends over the entire length of the cutting blade 4. This makes it possible to prevent loss more reliably.

  Next, the effect of the curvature radius of the convex curve formed by the connecting portion 4C as seen from the tip side in the axis O direction will be described with reference to examples. In this example, in the drill of the above-described embodiment shown in FIGS. 1 to 3 in which the cutting edge portion is formed of a diamond sintered body, the outer diameter D of the cutting blade 4 is 10 mm, and the convex arc formed by the connecting portion 4C is used. A drill with a radius R of 0.5 mm (0.05 × D) and a drill with a radius R of 1.0 mm (0.1 × D) were manufactured. In addition, the width of the honing surface 7 is 0.005 mm in all, and a minute chamfer is not formed in the intersecting ridge line portion 4D. These are sequentially referred to as Examples 1 and 2.

  Also, as a comparative example, thinning is not performed on the main cutting edge side of the thinning blade without forming a connecting part that forms a convex curve shape or a curved line shape that is in contact with the main cutting edge when viewed from the axial front end side. A drill similar to Examples 1 and 2 except that the blade and the main cutting edge were directly intersected at an angle (so-called pin caddy) and a drill in which the main cutting blade was not honed in this drill were also manufactured. . These are referred to as Comparative Examples 1 and 2 in this order. Then, according to Examples 1 and 2 and Comparative Examples 1 and 2, a through-hole is formed in a work material made of a composite material in which a CFRP (carbon fiber reinforced plastic) having a thickness of 5 mm and a titanium plate having a thickness of 10 mm are joined. Drilling was performed, and the presence or absence of a cutting edge defect was confirmed for each drilling. The machining conditions were a drill body 1 with a rotational speed of 15 m / min, a feed of 0.05 mm / rev, a step feed for each depth of 1 mm, and mist coolant was supplied from the coolant hole 5 at 0.5 MPa.

  As a result, in Comparative Examples 1 and 2, a defect occurred in the connecting portion during the processing of the first hole, resulting in a life failure. In Example 1, one hole was processed. In Example 2, it was possible to machine 5 holes. Incidentally, 10 holes can be machined under the same machining conditions when the radius R is 1.0 mm (0.1 × D) and the width of the honing surface 7 is 0.01 mm as in the second embodiment. When the width of 7 was 0.2 mm, 30 holes could be further processed. In addition, in the case where the width of the honing surface 7 was 0.2 mm and the radius R was 3.0 mm (0.3 × D), no defects were recognized even after 100 holes were machined, and the machining test was finished at that time. . Further, in the case where the radius R is set to 3.0 mm (0.3 × D), and the width of the honing surface 7 is increased to 0.4 mm, no defects were recognized even when 100 holes were processed, It was confirmed that burrs were generated from the beginning of processing.

DESCRIPTION OF SYMBOLS 1 Drill main body 2 Chip discharge groove 3 Tip flank 4 Cutting blade 4A Main cutting blade 4B Thinning blade 4C Connection part 4D Intersection ridgeline of honing surface 7 and tip flank 3 6 Thinning portion 6A Thinning surface 7 Honing surface O Drill body 1 axis T drill rotation direction R radius of curvature of the convex curve formed by the connecting portion 4C when viewed from the front end side in the axis O direction honing angle

Claims (3)

  A chip discharge groove is formed on the outer periphery of the tip end of the drill body rotated about the axis, and a cutting edge is formed at a crossed ridge line portion between the wall surface of the chip discharge groove facing the drill rotation direction and the tip flank of the drill body. The cutting blade has a main cutting edge extending from the outer peripheral end of the cutting blade to the inner peripheral side, and an inner peripheral portion of the wall surface facing the drill rotation direction of the chip discharge groove cut out to the axial line side. A thinning blade formed on the intersecting ridge line portion of the thinning portion facing the drill rotation direction of the thinning portion and the tip flank and connected to the inner periphery of the main cutting blade. The main cutting edge is connected to the main cutting edge via a connecting portion having a convex curve shape or a curved line consisting of a plurality of straight lines in contact with the main cutting edge when viewed from the front end side in the axial direction. Honing on the connection side The honing surface is formed, the honing angle of the honing surface is equal to the rake angle of the thinning blade by the thinning surface, and the honing surface and the thinning surface are smoothly continuous. Features a drill.   The radius of curvature of the convex curve formed by the connecting portion or the circle inscribed in the convex bent line when viewed from the front end side in the axial direction is 0.1 × D or more with respect to the outer diameter D of the cutting edge. The drill according to claim 1, wherein:   3. The drill according to claim 1, wherein a chamfer having a convex cross-sectional shape is applied to an intersecting ridge line portion between the honing surface and the tip flank. 4.

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