JP2018176360A - Rotary cutting hole drilling tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a rotary cutting type drilling tool having a low cutting resistance. SOLUTION: A plurality of twisted grooves are provided around an axial center, and a main cutting edge is formed along the twisted groove at a portion where each of the plurality of twisted grooves opens toward the tip, and thinning is formed at the tip. In a rotary cutting type drilling tool in which a thinning blade is formed as a ridge line connecting the end of the chisel edge and the end on the axial side of the main cutting edge, the radial rake angle of the thinning blade is a positive angle. And. The axial rake angle of the thinning blade can also be a positive angle. Preferably, these rake angles are 5-30 °. The shape of the thinning blade can be an arc shape in which the central portion is recessed from both ends. The shape of the thinning surface can be concave. [Selection diagram] Fig. 3

Description

  The present invention relates to a rotary cutting drilling tool. More particularly, the present invention relates to a rotary cutting drill bit having low cutting resistance.

  It is known in the art to reduce thrust resistance (thrust load) by applying thinning to shrink the width of a chisel edge for the purpose of improving the durability and stability of cutting performance of a twist drill. . Furthermore, by setting the rake angle of the thinning edge formed between the thinning groove and the flank surface of the drill tip to a negative angle, it is possible to compensate for the strength of the chisel edge and to suppress the wear on the rake surface of the thinning edge. Are also known (see, for example, Patent Document 1).

  In metalworking drills, the width of the negative land formed on the thinning edge is made larger than the width of the negative land formed on the main cutting edge for the purpose of reducing thrust resistance and improving biting and centripetal properties. It is also known to reduce the width of the chisel edge (see, for example, Patent Document 2).

JP 2008-213121 A JP, 2009-018360, A

  As described above, in the art, attempts have been made to improve cutting performance by reducing thrust resistance in a rotary cutting drilling tool such as a twist drill mainly by reducing the width of the chisel edge. According to such a prior art, when the rotational speed of the cutting tool is high, it is possible to achieve a reduction in thrust resistance and an improvement in cutting performance. However, when the rotational speed of the cutting tool is low, the thrust resistance is still high and the cutting performance is degraded. Further, as described above, if the rake angle of the thinning edge is set to a negative angle in order to compensate for the strength of the chisel edge portion, cutting resistance increases, and cutting performance decreases particularly when the rotational speed of the cutting tool is low.

  As described above, in the rotary cutting drilling tool according to the prior art, although the reduction of thrust resistance is attempted by reducing the width of the chisel edge, the effect is still insufficient. Thus, there is a need in the art for a rotary cutting drilling tool that can achieve low cutting resistance even when the rotational speed of the cutting tool is low. It is an object of the present invention to provide a rotary cutting drilling tool with low cutting resistance.

  As a result of earnest research, the inventor of the present invention, for example, in a rotary cutting drilling tool such as a twist drill with thinning applied to the center on the tip side, the thinning surface and the main cutting edge adjacent to the rear side in the rotational direction of the tool. It has been found that the cutting resistance (cutting load) of the tool can be significantly reduced by imparting machinability to the thinning edge formed at the ridge line intersecting with the flank surface.

  In view of the above, the rotary cutting type drilling tool according to the present invention (hereinafter sometimes referred to as “the inventive tool”) has a plurality of helical grooves around its axis, and the plurality of helical grooves A main cutting edge is formed along the twist groove at a portion that opens toward the tip, and thinning is applied to the center on the tip side, and the end of the chisel edge and the axial center side of the main cutting edge It is a rotary cutting-type drilling tool in which a thinning edge is formed as a ridge line connecting with the end of the blade. In the tool of the present invention, at least a radial rake angle of the thinning blade is a positive angle.

  In the inventive tool, the axial rake angle of the thinning blade may also be a positive angle. Furthermore, the shape of the thinning blade in a bottom view as viewed from the front end side may be an arc shape in which the central portion is recessed than the both end portions. In addition, the shape of the thinning surface may be concave in any of the radial direction and the rotational direction which is a direction orthogonal to the axis of the tool of the present invention.

  According to the tool of the present invention, by reducing the thrust resistance by reducing the width of the chisel edge by thinning, it is possible to significantly reduce the cutting resistance by providing the thinning blade with machinability.

  Other objects, other features and attendant advantages of the present invention will be readily understood from the description of embodiments of the present invention which will be described with reference to the following drawings.

FIG. 1 is a schematic front view of an exemplary twist drill according to the prior art. It is the (a) typical bottom view seen from the tip side of the example twist drill concerning a prior art, and the typical fragmentary enlarged view near the chisel edge (b). 1 is a schematic front view of an exemplary twist drill according to an embodiment of the present invention. It is the (a) typical bottom view seen from the tip side of the example twist drill concerning the example of the present invention, and the typical fragmentary enlarged view near the chisel edge (b). It is the photograph taken from the front of the example twist drill concerning the example of the present invention. It is the photograph taken from the tip side of the example twist drill concerning the example of the present invention. FIG. 7 is an enlarged photograph of the vicinity of the chisel edge of a photograph taken from the tip side of an exemplary twist drill according to the embodiment of the present invention shown in FIG. 6. (A) An exemplary twist drill according to the prior art and (b) a graph showing temporal transition of cutting load (thrust load) and cutting torque during cutting with an exemplary twist drill according to an embodiment of the present invention. .

First Embodiment
Hereinafter, a rotary cutting type drilling tool (hereinafter, may be referred to as a “first tool”) according to the first embodiment of the present invention will be described.

  In the first tool, a plurality of twist grooves are provided around the axis, and a main cutting edge is formed along the twist grooves in a portion where each of the plurality of twist grooves opens toward the tip, It is a rotary cutting drilling tool in which a thinning is formed as a ridge line connecting the end of a chisel edge and the end on the axial center side of a main cutting edge with a thinning at the center of. In other words, the term "thinning blade" refers to the crossing ridge line between the thinning surface, which is the surface defining the groove formed by thinning, and the flank surface of the main cutting blade adjacent to the rear side in the rotational direction of the tool. It is a blade formed in the part.

  In the present specification, "rotary cutting type drilling tool" refers to a tool for cutting a base material and drilling a hole in the base material by rotation of the tool, and is not limited to a general twist drill, for example, a drilled tap And various drilling tools including reamer etc. As a specific example of the material which comprises such a rotary cutting-type drilling tool, the cemented carbide which has tungsten carbide (tungsten carbide, WC) etc. as a main component etc. can be mentioned, for example. In addition, an amorphous carbon coating (for example, DLC (diamond like carbon) coating etc.) is formed on the surface of such a rotary cutting type drilling tool to improve performance such as wear resistance and adhesion resistance, for example. May be

  As described above, in the twist drill and the like according to the prior art, it is generally performed to set the rake angle of the thinning edge to a negative angle to compensate for the strength of the chisel edge portion. When the rake angle is thus set to a negative angle, cutting resistance is increased, and in particular, cutting performance is reduced when the rotational speed of the cutting tool is low.

  However, in the first tool, at least the radial rake angle of the thinning blade is a positive angle. As a result, good machinability in the radial direction can be imparted to the thinning edge, and as a result, cutting resistance of the first tool can be significantly reduced. In general, when the rake angle becomes positive (+), the sharpness of the blade improves and cutting resistance decreases, while the strength of the cutting edge decreases. On the other hand, when the rake angle becomes negative (-), the sharpness of the blade becomes worse and the cutting resistance increases, while the strength of the cutting edge increases. Therefore, the specific size of the radial rake angle of the thinning edge of the first tool is, for example, the material constituting the base material to be drilled by the first tool, the material constituting the first tool, and the cutting conditions It can be appropriately determined according to (for example, the rotational speed of the first tool, etc.).

  However, if the radial direction rake angle of the thinning edge of the first tool is an excessively large positive angle, the thickness of the thick part immediately below the chisel edge in the axial direction becomes excessively thin or the thick part becomes discontinuous. As a result, there is a possibility that the mechanical strength of the tip portion may be insufficient or it may be difficult to support the tip portion. From such a viewpoint, it is preferable that the radial direction rake angle of the thinning edge of the first tool be 30 ° or less.

  On the other hand, if the radial direction rake angle of the thinning edge of the first tool is a positive angle, good machinability in the radial direction can be imparted to the thinning edge, as a result, the cutting resistance of the first tool is significantly increased. It can be reduced. In order to reliably impart good machinability in the radial direction by the thinning blade, the radial rake angle of the thinning blade of the first tool is more preferably 5 ° or more.

Second Embodiment
Hereinafter, the rotary cutting type drilling tool (Hereinafter, it may be called a "2nd tool") concerning a 2nd embodiment of the present invention is explained.

  The second tool is a rotary cutting drilling tool having the same configuration as the first tool described above, except that the axial rake angle of the thinning blade is also a positive angle. Thereby, good machinability in the axial direction can be imparted to the thinning blade, and as a result, the cutting resistance of the second tool can be significantly reduced. The specific size of the axial rake angle of the thinning edge of the second tool also depends, for example, on the material constituting the base material to be drilled by the second tool, the material constituting the second tool and the cutting conditions. Can be determined accordingly.

  However, if the axial rake angle of the thinning edge of the second tool is also an excessively large positive angle, the thickness of the thick portion immediately below the chisel edge in the axial direction becomes excessively thin or the thick portion becomes discontinuous. As a result, there is a possibility that the mechanical strength of the tip end may be insufficient or it may be difficult to support the tip end. From such a point of view, the axial rake angle of the thinning edge of the second tool is also preferably 30 ° or less.

  On the other hand, if the axial rake angle of the thinning edge of the second tool is a positive angle, good machinability in the axial direction can be imparted to the thinning edge, as a result, the cutting resistance of the second tool is significantly increased. It can be reduced. It is more preferable that the axial direction rake angle of the thinning edge of the second tool be 5 ° or more in order to reliably impart good machinability in the axial direction by the thinning edge.

Third Embodiment
Hereinafter, a rotary cutting type drilling tool (hereinafter, may be referred to as “third tool”) according to a third embodiment of the present invention will be described.

  The third tool has the same configuration as the first tool and the second tool described above except that the shape of the thinning blade in a bottom view as viewed from the tip side is an arc-like shape in which the central portion is recessed from both ends. A rotary cutting drilling tool having According to this, it is possible to further improve the machinability of the third tool by the synergetic effect with the design of the rake angle of the thinning edge in the first tool and the second tool.

  The specific shape of the thinning edge of the third tool, such as the radius of the arc-like shape, is, for example, the material constituting the base material to be punctured by the third tool, the material constituting the third tool, It can be appropriately determined in accordance with the cutting conditions (for example, the rotational speed of the third tool, etc.).

Fourth Embodiment
Hereinafter, a rotary cutting type drilling tool (hereinafter, may be referred to as “fourth tool”) according to the fourth embodiment of the present invention will be described.

  The fourth tool has the above-described first to third tools except that the shape of the line of intersection between the plane including the axis of the fourth tool and the thinning surface formed at the tip is a curve which is recessed toward the tip. It is a rotary cutting-type drilling tool having the same configuration as in the above.

  In a rotary cutting type drilling tool according to the prior art, it is general to apply thinning by the side surface of the grindstone while rotating a simple cylindrical grindstone. Therefore, the shape of the line of intersection between the plane including the axis of the tool and the thinning surface formed at the tip is generally straight or substantially straight. As a result, the number of lands removed by thinning increases. For example, in the case where a margin (guide) is formed on the land portion of the drill, it is necessary to increase the width of the margin in anticipation of the portion to be scraped off by thinning. As a result, there is a problem that the frictional resistance between the inner wall of the hole and the tool at the time of cutting is increased.

  However, in the fourth tool, the shape of the line of intersection between the plane including the axis of the fourth tool and the thinning surface formed at the tip is a curve that is recessed toward the tip. In other words, the position of the end on the outer peripheral side of the intersection line between the plane including the axis of the fourth tool and the thinning surface is on the tip side of the fourth tool than the central part of the intersection line. As a result, the margin to be scraped off by thinning can be reduced, and hence the width of the margin can be reduced, so that the frictional resistance between the inner wall of the hole and the drill during cutting can be reduced.

  Here, regarding the configuration and effects of the rotary cutting type drilling tool according to the embodiment of the present invention (hereinafter, may be referred to as "the embodiment tool"), the rotary cutting type drilling according to the prior art as a comparative example. A detailed description will be given in comparison with the configuration and effects of a tool (hereinafter sometimes referred to as “conventional tool”).

<Configuration of conventional tools>
Prior to the description of the example tool, the configuration of a conventional tool will first be described in order to assist in the understanding of the present invention. Here, a two-blade twist drill will be described as an example of a rotary cutting drilling tool.

  FIG. 1 is a schematic front view of an exemplary twist drill 100 according to the prior art. On the other hand, FIG. 2 is (a) a schematic bottom view and (b) a schematic partial enlarged view in the vicinity of the chisel edge when the twist drill 100 is viewed from the tip side. The twist drill 100 has two twist grooves 110 provided around the axis Ax, and each of the two twist grooves 110 opens toward the tip (upper side in FIG. 1 and front side in FIG. 2). Main cutting edges 120 are respectively formed along the twist groove 110 in the part.

  A flank 130 is formed on the tip side of each cutting edge 120. Further, a heel 140 is formed on the opposite side to the cutting edge 120 with the twist groove 110 (i.e., the outer side end of the twist groove 110). The outer surface of the portion of the twist drill 100 where the twist groove 110 is not formed constitutes a land portion 150.

  The side surface of a simple cylindrical grinding wheel (not shown) rotating about a rotation axis perpendicular to (radially parallel to) the axial direction of the twist drill 100 twist drills so-called "X-shaped" thinning It was applied to the center on the 100 tip side. As a result, as shown in FIG. 2A, which is an enlarged view of a portion surrounded by a broken line in FIG. 2A, the chisel edge 190 (thick line portion) becomes short, and the end of the chisel edge 190 and the main cutting edge 120 A thinning edge 170 is formed as a straight ridge line connecting the end portion on the axial center side. The rake surface 161 of the thinning blade 170 is formed such that the rake angle of the thinning blade 170 becomes a negative angle to compensate for the strength of the chisel edge 190.

  When the rake angle of the thinning blade 170 is set to a negative angle as described above, as described above, the cutting resistance is increased, and the cutting performance particularly decreases when the rotational speed of the cutting tool is low. In addition, since the chip pocket (clearance) has a small bowl shape (see the shaded area shown in (b) of FIG. 2), the dischargeability of chips from the central portion tends to be insufficient.

  The thinning surface 162 is formed in a substantially planar shape, and the crossing ridge line between the thinning surface 162 and the flank surface 130 is a straight line, so the leading end side of the land portion 150 is largely scraped off by thinning. In other words, the position of the intersection point 141 between the thinning surface 162 and the heel 140 is far from the tip of the twist drill 100 (the guide retraction amount ΔG shown in FIG. 1 is large). For this reason, when forming a margin on the tip end side of the land portion 150, it is necessary to form the width of the margin wide in anticipation of the portion to be scraped off by thinning. Thereby, the loss of the margin on the tip side due to thinning is avoided, but there is a possibility that the frictional resistance between the inner wall of the hole and the twist drill 100 at the time of cutting may be increased.

<Configuration of Example Tool>
Next, the configuration of the example tool will be described first. In the following description, the example tool is also described as being a two-blade twist drill similar to the above-described conventional tool.

  FIG. 3 is a schematic front view of an exemplary twist drill 200 according to an embodiment of the present invention. On the other hand, FIG. 4 is (a) a schematic bottom view and (b) a schematic partial enlarged view in the vicinity of the chisel edge when the twist drill 200 is viewed from the tip side. The twist drill 200 has two twist grooves 210 provided around the axis Ax, and each of the two twist grooves 210 opens toward the tip (upper side in FIG. 3 and front side in FIG. 4). Main cutting edges 220 are respectively formed along the twist groove 210 in the part.

  A flank surface 230 is formed on the tip side of each cutting edge 220. Further, a heel 240 is formed on the opposite side to the cutting edge 220 across the twist groove 210 (that is, the outer side end of the twist groove 210). The outer surface of the portion of the twist drill 200 where the twist groove 110 is not formed constitutes a land 250.

  Thinning was applied to the center on the tip side of the twist drill 200 by the side surface of a cylindrical grindstone (not shown) rotating around a rotation axis inclined with respect to the axial direction and the radial direction of the twist drill 200. The side surface of the cross section of the grinding wheel according to the plane including the rotation axis has an arc shape. As a result, the rake surface 261 of the thinning blade 270 is formed such that both the radial rake angle and the axial rake angle of the thinning blade 270 become positive angles to impart machinability to the thinning blade 270. Thereby, the machinability of the thinning blade 270 can be improved. In addition, since a larger (wide) tip pocket (clearance) can be formed as compared with the case where the rake angle is a negative angle (see the shaded area shown in (b) of FIG. 4), the center is formed. It is also possible to improve the discharge of chips from the part.

  As shown in FIG. 4A which is an enlarged view of a portion surrounded by a broken line in FIG. 4A, the chisel edge 290 (thick line portion) is shortened, and the end of the chisel edge 290 and the axial center side of the main cutting edge 220 The thinning blade 270 is formed as a curved ridge line connecting the end of the blade. Specifically, the shape of the thinning blade 270 is an arc shape in which the central part is recessed from the both ends, whereby the machinability of the twist drill 200 is further enhanced by the synergetic effect with the design of the rake angle of the thinning blade 270. It can be improved.

  The thinning surface 260 is formed in the shape of a curved surface in which the central portion is recessed, and the shape of the intersection line between the plane including the axis Ax of the twist drill 200 and the thinning surface 260 is a curved surface recessed toward the tip. Furthermore, the shape of the line of intersection between the plane orthogonal to the axis Ax of the twist drill 200 and the thinning surface 260 is a curve that is recessed rearward on the rotational direction of the twist drill 200 (counterclockwise in FIG. 4). As a result, the amount by which the tip end side of the land portion 150 is scraped off by thinning is smaller than that of the above-described conventional twist drill 100. In other words, the position of the intersection point 241 between the thinning surface 260 and the heel 240 is closer to the tip of the twist drill 200 than in the twist drill 100 according to the prior art (the guide retraction amount ΔG shown in FIG. 3 is small). For this reason, in the twist drill 200 according to the embodiment, when forming a margin on the tip end side of the land 250, the extent to which the width of the margin is formed wide in anticipation of the portion scraped off by thinning is the twist according to the prior art. Small compared to drill 100. As a result, it is possible to reduce the frictional resistance between the inner wall of the hole and the twist drill 200 at the time of cutting while avoiding the loss of the margin on the tip side due to thinning.

  Photographs of the appearance of an exemplary twist drill 200 according to an embodiment of the present invention having the configuration as described above are shown in FIGS. 5 to 7. FIG. 5 is a photograph taken from the front of the twist drill 200. In the present example, the twist drill 200 was manufactured as a drill formed at the tip of the tap. 6 is a photograph taken from the tip side of the twist drill 200, and FIG. 7 is an enlarged photograph of the vicinity of the chisel edge of the photograph shown in FIG.

  In the present example, thinning was performed using a grindstone having a specific shape to manufacture the twist drill 200 having the shape as described above, but the method of manufacturing a rotary cutting type drilling tool according to the present invention is the above It is needless to say that the rotary cutting drilling tool according to the present invention may be manufactured by any method known to those skilled in the art without limitation to the above.

Comparison of Conventional Tool and Example Tool
Cutting is actually performed using an exemplary twist drill 100 according to the prior art having the configuration as described above and an exemplary twist drill 200 according to an embodiment of the present invention, and the cutting load at that time (thrust load) And the results of measuring the cutting torque are shown in the graph of FIG.

  In the twist drill 100 according to the prior art shown in FIG. 8A, both the cutting load (graph drawn above by solid line) and cutting torque (graph drawn below by dashed line) show large values. It has been confirmed that a further reduction of the cutting resistance is necessary.

  On the other hand, in the twist drill 200 according to the embodiment of the present invention shown in (b) of FIG. 8, any of the cutting load (graph drawn above by solid line) and cutting torque (graph drawn below by broken line) Even in comparison with the twist drill 100 described above, it is significantly reduced. In particular, the cutting load during cutting with the twist drill 200 was approximately 50% of the cutting load during cutting with the twist drill 100.

  As described above, according to the present invention, it was confirmed that the cutting resistance of the rotary cutting drilling tool can be effectively reduced. A rotary cutting drilling tool exhibiting such a low cutting resistance can perform cutting, for example, at a higher cutting speed as compared to a rotary cutting drilling tool exhibiting a high cutting resistance. That is, productivity in cutting can be enhanced.

  Although several embodiments and examples having specific configurations have been described above for the purpose of describing the present invention, the scope of the present invention is limited to these exemplary embodiments and examples. It should not be interpreted as being, and it can not be overemphasized that it is possible to add an amendment suitably, within the limits indicated to a claim and a specification.

  DESCRIPTION OF SYMBOLS 100 ... twist drill (conventional technology), 110 ... torsion groove (conventional technology), 120 ... cutting edge (conventional technology), 130 ... flank surface (conventional technology), 140 ... heel (conventional technology), 141 ... thinning surface and heel Intersections with prior art (prior art), 150 lands (prior art), 160 and 162 ... thinning surfaces (conventional art), 161 ... rake surfaces by thinning (prior art), 170 ... thinning edges (prior art), 190 ... Chisel edge (prior art), 200: twist drill (invention), 210: twist groove (invention), 220: cutting edge (invention), 230: flank surface (invention), 240: heel (invention), 241 · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · · Rusukui surface (present invention), 270 ... thinning edge (present invention), and 290 ... chisel edge (present invention).

Claims (8)

A plurality of twist grooves are provided around the axial center, and a main cutting edge is formed along the twist grooves at a portion where each of the plurality of twist grooves opens toward the tip, and the tip is thinned A rotary cutting drilling tool in which a thinning edge is formed as a ridge line connecting an end of a chisel edge and an end of the main cutting edge on the axial center side,
At least a radial rake angle of the thinning blade is a positive angle,
Rotary cutting drilling tool. A rotary cutting drilling tool according to claim 1, wherein
The radial direction rake angle of the thinning blade is 30 ° or less.
Rotary cutting drilling tool. A rotary cutting drilling tool according to claim 1 or claim 2, wherein
The radial direction rake angle of the thinning blade is 5 ° or more.
Rotary cutting drilling tool. A rotary cutting-type drilling tool according to any one of claims 1 to 3, wherein
The axial rake angle of the thinning blade is also a positive angle,
Rotary cutting drilling tool. 5. The rotary cutting drilling tool according to claim 4, wherein
The axial rake angle of the thinning blade is 30 ° or less.
Rotary cutting drilling tool. A rotary cutting drilling tool according to claim 4 or claim 5, wherein
The axial rake angle of the thinning blade is 5 ° or more.
Rotary cutting drilling tool. A rotary cutting-type drilling tool according to any one of claims 1 to 6, wherein
The shape of the thinning blade in a bottom view as viewed from the tip end is an arc shape in which a central portion is recessed relative to both ends.
Rotary cutting drilling tool. A rotary cutting drilling tool according to any one of claims 1 to 7, wherein
The shape of the line of intersection between the plane including the axis of the rotary cutting drilling tool and the thinning surface formed at the tip is a curve which is recessed toward the tip.
Rotary cutting drilling tool.