JP2009136998A - Drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drill increased in tool life while enhancing chip discharging property. <P>SOLUTION: In this drill 1, the groove bottom part 4a of a chip discharge groove 4 is formed in an arcuate shape curved in the axis O direction when viewed from a section perpendicular to the axis O direction, and the radius R of the groove bottom part is set to 2D where D is the diameter of a tool body 2. Therefore, the chips near the groove bottom part 4a can be smoothly discharged, and the discharge resistance of the chips and the cutting resistance of the drill can be suppressed. Consequently, since the discharge resistance of the chips and the cutting resistance of the drill are suppressed, the life of the tool can be increased while enhancing the chip discharging property. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a drill, and more particularly to a drill that can improve tool life while improving chip discharge performance.

  Conventionally, a drill is provided with a chip discharge groove for receiving and discharging chips generated during cutting. Generally, a drill can increase the chip discharge property by taking a large cross-sectional area of the chip discharge groove and enlarging the chip pocket.

As a technique for enlarging a chip pocket, for example, Patent Document 1 discloses a twist drill for deep hole machining in which a tool cross-sectional shape (cross-sectional shape perpendicular to the axial direction) is substantially S-shaped.
Japanese Utility Model Publication No. 60-12648

  However, the twist drill for deep hole processing disclosed in Patent Document 1 can improve the chip discharging performance, but the tool cross-sectional area is increased to a substantially S-shape so that the chip pocket can be enlarged. There is a problem that the tool life is shortened due to a decrease in tool rigidity.

  The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a drill that can improve tool life while improving chip discharge performance.

  In order to achieve this object, a drill according to claim 1 comprises a tool body rotating about an axis, a cutting edge provided at a tip of the tool body, a rake face of the cutting edge, and the tool body. A chip discharge groove that is recessed in the outer peripheral surface of the tool body and extends from the front end to the rear end side of the tool body, and the chip discharge groove includes a groove bottom portion that forms a groove bottom, The groove bottom portion is formed in an arc shape that curves in the axial direction in a cross-sectional view perpendicular to the axial direction, and the radius thereof is set to 2D or more with respect to the diameter D of the tool body. .

  The drill according to claim 2 is the drill according to claim 1, wherein the chip discharge groove is connected to the bottom of the groove and forms a wall surface facing the rotation direction of the tool body, and A second wall surface portion that forms a wall surface that is continuous with the groove bottom portion and faces rearward in the rotation direction of the tool body, and the first wall surface portion and the second wall surface portion are in a cross-sectional view perpendicular to the axial direction. Each of the first wall surface portion and the second wall surface portion is formed substantially in parallel with each other.

  The drill according to claim 3 is the drill according to claim 1 or 2, wherein a groove length of the chip discharge groove is set to 20D or more with respect to a diameter D of the tool body.

  The drill according to claim 4 is the drill according to any one of claims 1 to 3, wherein the thickness of the web formed by the groove bottom of the chip discharge groove is directed from the front end side to the rear end side of the tool body. The taper portion is configured to be gradually thinner according to the tool body, the taper portion being provided with a predetermined width along the axial direction from the tip of the tool body, and the predetermined width with respect to the diameter D of the tool body. 3D or more and 4D or less, and the amount of change in the thickness of the web from the front end to the rear end side of the tool body at the tapered portion is 0.02D or less with respect to the diameter D of the tool body. Is set to

  The drill according to claim 5 is the drill according to any one of claims 1 to 4, wherein the thickness of the web at the tip of the tool body is 0.35D or more and 0. It is set within a range of 45D or less.

  The drill according to claim 6 is the drill according to any one of claims 1 to 5, wherein the chip discharge groove is formed by being twisted around the axis, and the twist angle thereof is not less than 35 degrees and not more than 45 degrees. It is set within the range.

  According to the drill of claim 1, the chip discharge groove includes a groove bottom portion that forms a groove bottom, and the groove bottom portion has an arc shape that curves in the axial direction in a cross-sectional view perpendicular to the axial direction. The radius is set to 2D or more with respect to the diameter D of the tool body. Therefore, chips near the groove bottom can be discharged smoothly, and the chip discharge resistance and cutting resistance can be suppressed.

  That is, when the radius of the groove bottom is set to be smaller than 2D with respect to the diameter D of the tool body, the chips are likely to curl in the direction opposite to the rotation direction of the tool body, and chip discharge resistance and cutting When the resistance increases, according to the present invention, by setting the radius of the groove bottom to 2D or more with respect to the diameter D of the tool body, chips near the groove bottom can be smoothly moved along the rotation direction of the tool body. Since it can discharge | emit, chip | tip discharge resistance and cutting resistance can be suppressed.

  As a result, by suppressing the chip discharge resistance and the cutting resistance, there is an effect that the tool life can be increased while the chip discharge performance is improved.

  According to the drill of Claim 2, in addition to the effect which the drill of Claim 1 produces | generates, a chip | tip discharge groove | channel is a 1st wall surface part which comprises the wall surface which is continuously provided in the groove bottom part and faces the rotation direction of a tool main body. And a second wall surface portion that forms a wall surface that is continuous with the groove bottom portion and faces the back in the rotational direction of the tool body, and the first wall surface portion and the second wall surface portion are each in a cross-sectional view perpendicular to the axial direction. Since the first wall surface portion and the second wall surface portion are formed substantially in parallel with each other, the tool wall rigidity can be ensured while the chip pocket is enlarged. .

  That is, when trying to expand the chip pocket, it is necessary to reduce the tool cross-sectional area, and accordingly, the tool rigidity is reduced, while when trying to secure the tool rigidity, it is necessary to increase the tool cross-sectional area. As a result, the chip pocket cannot be secured sufficiently, and it has been difficult to achieve both expansion of the chip pocket and tool rigidity.

  On the other hand, according to the present invention, the first wall surface portion and the second wall surface portion are formed substantially linearly in a cross-sectional view perpendicular to the axial direction, and the first wall surface portion and the second wall surface portion are mutually connected. By configuring substantially parallel to each other, the chip pocket can be enlarged, and the first wall surface portion and the second wall surface portion are formed in a substantially linear shape, and the first wall surface portion and the second wall surface portion are substantially mutually connected. Since the tip pocket is enlarged by configuring in parallel, for example, the tool cross-sectional area is excessively reduced as compared to the case where the cross-sectional shape is made substantially S-shaped so as to reduce the tool cross-sectional area and the chip pocket is enlarged. Therefore, the rigidity of the tool can be ensured.

  As a result, there is an effect that it is possible to increase the tool life while improving the chip discharging property by securing the rigidity of the tool while expanding the chip pocket.

  Further, in addition to forming the first wall surface portion and the second wall surface portion in a substantially straight shape in a cross-sectional view perpendicular to the axial direction, the first wall surface portion and the second wall surface portion are configured to be substantially parallel to each other, By setting the radius of the groove bottom to 2D or more with respect to the diameter D of the tool body, each effect can be exhibited synergistically, and the tool life can be improved while further improving the chip discharge performance. There is an effect that the lifetime can be further increased.

  According to the drill of Claim 3, in addition to the effect which the drill of Claim 1 or 2 has, the groove length of the chip discharge groove is set to 20D or more with respect to the diameter D of the tool body. Here, the groove length of the chip discharge groove is determined by the sum of the depth of the machining hole and a margin for discharging chips (generally, about 1.5D to 2D). Therefore, according to this invention, the deep hole more than 18D can be processed with respect to the diameter D of a tool main body.

  In addition, by setting the groove length of the chip discharge groove to 20D or more with respect to the diameter D of the tool body, it is difficult to discharge the chips as compared with the case where the diameter D of the tool body is smaller than 20D. In the processing of a deep hole, there is an effect that the effect of improving the chip discharge property can be effectively exhibited.

  Furthermore, if such an effect can be effectively exhibited, even in deep hole machining, there is no need to perform stepwise drilling while repeating feed and return, so-called step machining is performed, and the machining efficiency is improved. There is an effect that can be.

  According to the drill of the fourth aspect, in addition to the effect achieved by the drill according to any one of the first to third aspects, the thickness of the web formed by the groove bottom of the chip discharge groove is increased from the front end side of the tool body. Since the taper portion configured to gradually become thinner toward the end side is provided, the tip pocket on the rear end side can be secured larger than the front end side of the tool body in the taper portion. Therefore, it is possible to smoothly discharge the chips that gradually increase in size toward the rear end side of the tool body, and to suppress clogging of chips in the chip discharge groove.

  The tapered portion is provided with a predetermined width along the axial direction from the tip of the tool body, and the predetermined width is set within a range of 3D or more and 4D or less with respect to the diameter D of the tool body. Here, when the predetermined width is set to be smaller than 3D with respect to the diameter D of the tool body, the range of the tapered portion becomes narrow, and a chip pocket cannot be secured sufficiently. By making it 3D or more, there is an effect that a sufficiently large chip pocket can be secured.

  On the other hand, when the predetermined width is set to be larger than 4D with respect to the diameter D of the tool body, the range of the tapered portion becomes too wide and the tool rigidity is lowered. By setting it as the following, there exists an effect that tool rigidity can be ensured.

  Further, since the change amount of the web thickness from the front end to the rear end side of the tool main body at the taper portion is set to 0.02 D or less with respect to the diameter D of the tool main body, the change amount is set to the tool main body. Compared with the case where the diameter D is set to be larger than 0.02D, the tool rigidity can be ensured and breakage can be prevented.

  According to the drill of claim 5, in addition to the effect of the drill of claim 4, the web thickness at the tip of the tool body is 0.35D or more and 0.45D with respect to the diameter D of the tool body. Since it is set within the range, there is an effect that a sufficiently large tip pocket can be secured while securing the tool rigidity.

  That is, when the thickness of the web is set to be smaller than 0.35D with respect to the diameter D of the tool body, the tool cross-sectional area decreases and the tool rigidity is reduced. On the other hand, tool rigidity can be ensured by setting it as 0.35D or more.

  On the other hand, when the thickness of the web is set to be thicker than 0.45D with respect to the diameter D of the tool body, the tool cross-sectional area increases and the chip pocket cannot be secured sufficiently. By setting it to 0.45 D or less with respect to D, a sufficiently large chip pocket can be secured.

  According to the drill of the sixth aspect, in addition to the effect produced by the drill according to any one of the first to fifth aspects, the chip discharge groove is formed by twisting around the axis and the twist angle thereof is 35 degrees or more. And since it is set within the range of 45 degrees or less, there is an effect that cutting resistance can be suppressed and clogging of chips in the chip discharge groove can be suppressed.

  In other words, when the twist angle is set to be smaller than 35 degrees, a large force is applied to the rake face by the chips and the cutting resistance is increased. it can.

  On the other hand, when the twist angle is set larger than 45 degrees, the path of the chip discharge groove becomes long and the chips are likely to be clogged. Clogging can be suppressed.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of the invention will be described with reference to the accompanying drawings. FIG. 1 is a front view of a drill 1 according to an embodiment of the present invention. In FIG. 1, a part of the length of the tool body 2 in the direction of the axis O is omitted, and the rotation direction of the drill 1 is indicated by an arrow A. In FIG. 1, the two-dot chain line used to indicate the twist angle α of the chip discharge groove 4 represents the axis O.

  First, a schematic configuration of the drill 1 will be described with reference to FIG. The drill 1 is a cutting tool for drilling a workpiece by rotational force transmitted from a processing machine (not shown) such as a machining center, and is a cemented carbide obtained by pressure-sintering tungsten carbide (WC) or the like. It is composed as a solid drill. As shown in FIG. 1, the drill 1 includes a tool main body 2, two cutting edges 3 provided at the tip of the tool main body 2 (the left end in FIG. 1), and the two cutting edges 3. And two chip discharge grooves 4 that are recessed in the outer peripheral surface of the tool body 2.

  The tool main body 2 is formed in a columnar shape having an axis O and a diameter D (D = 5 mm in the present embodiment), and a shank 2a is provided on the rear end side (right side in FIG. 1). The shank 2a is held by a holder (not shown), whereby the drill 1 is attached to the processing machine via the holder. Then, the rotational force of the processing machine is transmitted to the tool main body 2 through the holder, whereby the drill 1 (tool main body 2) rotates around the axis O in the arrow A direction.

  The cutting edge 3 is for cutting the workpiece by the rotational force transmitted from the processing machine, and the two cutting edges 3 are provided with the axis O symmetrically. The two cutting edges 3 are each formed in a straight line shape and parallel to each other when viewed from the front end direction of the tool body 2 (viewed from the left side in FIG. 1).

  The chip discharge groove 4 constitutes a rake face of the cutting edge 3 and accommodates and discharges chips generated by the cutting edge 3 at the time of cutting, and a twist angle α (in this embodiment, α = 38 degrees) and twisted (spiral) around the axis O, and the two chip discharge grooves 4 are provided symmetrically about the axis O.

  Here, it is desirable to set the twist angle α within the range of 35 degrees or more and 45 degrees or less. That is, when the torsion angle α is set to be smaller than 35 degrees, a large force is applied to the rake face by the chips, and the cutting resistance increases. it can.

  On the other hand, when the twist angle α is set to be larger than 45 degrees, the chip discharge groove 4 becomes longer and the chips are easily clogged. It is possible to suppress clogging of trash.

  The chip discharge groove 4 extends from the front end to the rear end side of the tool body 2 and has a length along the axis O direction, that is, a so-called groove length L, which is 30D with respect to the diameter D of the tool body 2. (That is, L = 150 mm in the present embodiment).

  Here, the groove length L is determined by the sum of the depth of the processed hole and a margin (generally about 1.5D to 2D) for discharging chips. Therefore, according to the drill 1 in the present embodiment, it is possible to process a deep hole of 28D or more with respect to the diameter D of the tool body 2. The detailed configuration of the chip discharge groove 4 will be described later with reference to FIGS. 2 and 3.

  In addition to the cutting edge 3 and the chip discharge groove 4, the tool body 2 is provided with a flank 5 and a second picking surface 6. The flank 5 is for reducing the contact area between the tip of the tool body 2 and the work piece during cutting and suppressing cutting resistance, and is provided continuously with the cutting edge 3. That is, the cutting edge 3 is constituted by the line of intersection between the flank 5 and the chip discharge groove 4.

  The second picking surface 6 is for reducing the contact area between the outer peripheral surface of the tool main body 2 and the workpiece during cutting and suppressing cutting resistance, and is continuous with the chip discharge groove 4. Thereby, a margin 7 is provided on the outer peripheral surface of the tool body 2 as the remaining portion of the second picking surface 6.

  The margin 7 is for polishing the inner wall surface of the hole to be machined, and the leading edge 8 is constituted by the intersection line between the margin 7 and the chip discharge groove 4. The twist angle α of the chip discharge groove 4 described above is an angle formed by the leading edge 8 and the axis O.

  Next, the detailed configuration of the chip discharge groove 4 will be described with reference to FIGS. 2 and 3. 2 is an enlarged cross-sectional view of the drill 1 perpendicular to the direction of the axis O in the line II-II in FIG. In FIG. 2, the outer shape of the tool body 2 is omitted, and the rotation direction of the drill 1 is indicated by an arrow A.

  As shown in FIG. 2, the chip discharge groove 4 includes a groove bottom portion 4 a constituting the groove bottom, and a wall surface (so-called rake face) that is continuous with the end portion Pb of the groove bottom portion 4 a and faces the arrow A direction. A first wall surface portion 4b to be configured, and a second wall surface portion 4c which is connected to the end portion Pc of the groove bottom portion 4a and which faces the rear side in the arrow A direction (counter arrow A direction) are configured. Yes.

  As shown in FIG. 2, the groove bottom 4 a is formed in an arc shape that curves in the direction of the axis O in a cross-sectional view perpendicular to the direction of the axis O, and its radius R is relative to the diameter D of the tool body 2. 2D (that is, R = 10 mm in the present embodiment).

  Further, the groove bottom portion 4a is centered on the axis O in a cross-sectional view perpendicular to the direction of the axis O, and has a diameter Q of 0.5D with respect to the diameter D of the tool body 2 (that is, Q in the present embodiment). = 2.5 mm) is provided in a region within the virtual circle C. That is, the end portions Pb and Pc are configured to be positioned on the virtual circle C.

  Here, the diameter Q of the virtual circle C is not limited to 0.5D with respect to the diameter D of the tool body 2 as in the present embodiment, but 0.5D with respect to the diameter D of the tool body 2. It is desirable to set within the following range.

  That is, when the diameter Q of the virtual circle C is set to be larger than 0.5D with respect to the diameter D of the tool body 2, the range of the groove bottom portion 4a becomes too wide and the chips are opposite to the direction of the arrow A. It becomes easy to curl to the side, and the chip discharge resistance and cutting resistance increase. By making the diameter D of the tool body 2 0.5 D or less, the chips near the groove bottom 4 a are moved in the direction of arrow A. It is possible to smoothly discharge along, and to suppress chip discharge resistance and cutting resistance.

  As shown in FIG. 2, the first wall surface portion 4 b and the second wall surface portion 4 c are each formed in a straight line shape in a cross-sectional view perpendicular to the direction of the axis O, and the first wall surface portion 4 b and the second wall surface portion. 4c is configured in parallel with each other.

  Here, in this embodiment, since the two chip discharge grooves 4 are provided symmetrically with the axis O as described above, one of the two chip discharge grooves 4 of the two chip discharge grooves 4 is provided. The relationship between the first wall surface portion 4b and the second wall surface portion 4c of the other chip discharge groove 4 is also parallel to each other. Similarly, the first wall surface portion 4b of the other chip discharge groove 4 and the first wall surface portion 4b of the one chip discharge groove 4 are the same. The relationship with the two wall surfaces 4c is also parallel to each other. Therefore, as shown in FIG. 2, the drill 1 has a substantially rectangular cross-sectional shape perpendicular to the direction of the axis O.

  The first wall surface portion 4b is configured to contact the groove bottom portion 4a with the end portion Pb as a contact in a cross-sectional view perpendicular to the direction of the axis O, and the second wall surface portion 4c is an imaginary portion extending from the first wall surface portion 4b. It is configured to be provided behind the line in the direction of arrow A. That is, the chip discharge groove 4 is configured not to undergo a sudden shape change. As a result, the chips can smoothly flow from the first wall surface portion 4b to the second wall surface portion 4c along the groove bottom portion 4a, and the chip discharge performance can be improved.

  As shown in FIG. 2, the web 9 is left as a center between the groove bottom portions 4 a of the two chip discharge grooves 4 (that is, the web 9 is formed by the groove bottom of the chip discharge grooves 4. ing). Here, the web 9 will be described with reference to FIG.

  FIG. 3 is an enlarged cross-sectional view in which the rotation locus of the groove bottom of the chip discharge groove 4 is viewed in cross section. In addition, in FIG. 3, while showing the rotation locus | trajectory of the external shape of the tool main body 2 using a two-point difference line, the rear end side (right side of FIG. 3) of the tool main body 2 is abbreviate | omitted and illustrated.

  As shown in FIG. 3, the thickness T (so-called core thickness) of the web 9 at the tip of the tool body 2 (the left end of FIG. 3) is 0.4D (that is, the diameter D of the tool body 2). In the present embodiment, T = 2 mm).

  Here, the thickness T of the web 9 at the tip of the tool body 2 is not limited to 0.4D with respect to the diameter D of the tool body 2 as in the present embodiment. Is preferably set within a range of 0.35D or more and 0.4D or less.

  That is, when the thickness T of the web 9 is set to be smaller than 0.35D with respect to the diameter D of the tool body 2, the tool cross-sectional area is reduced and the tool rigidity is lowered. By setting the diameter D to 0.35 D or more with respect to the diameter D, the tool rigidity can be ensured.

  On the other hand, when the thickness T of the web 9 is set to be greater than 0.45D with respect to the diameter D of the tool body 2, the tool cross-sectional area is increased, and a chip pocket cannot be sufficiently secured. By setting the diameter D to 0.45 D or less with respect to the diameter D of the main body 2, a sufficiently large chip pocket can be secured.

  Further, as shown in FIG. 3, the drill 1 is configured such that the thickness of the web 9 gradually decreases from the front end side (left side in FIG. 3) to the rear end side (right side in FIG. 3) of the tool body 2. A tapered portion 10 is provided.

  The taper portion 10 is provided with a predetermined width W along the axis O from the front end to the end portion Pt of the tool body 2, and the predetermined width W is 3.5 D (that is, the main body 2) with respect to the diameter D of the tool body 2. In the embodiment, W = 17.5 mm). That is, the end portion Pt is set at a position separated by 3.5D from the front end to the rear end side of the tool body 2.

  Thereby, since the tip pocket of the rear end side can be secured larger than the front end side of the tool body 2 in the taper portion 10, the chips that gradually increase in size toward the rear end side of the tool body 2 can be smoothly smoothed. It is possible to discharge, and clogging of chips in the chip discharge groove 4 can be suppressed.

  Here, the predetermined width W is not limited to 3.5D with respect to the diameter D of the tool body 2 as in the present embodiment, but the tool body 2 has 3D or more and 4D or less with respect to the diameter D. It is desirable to set within the range.

  That is, when the predetermined width W is set to be smaller than 3D with respect to the diameter D of the tool body 2, the range of the taper portion 10 becomes narrow, and the tip pocket cannot be secured sufficiently. On the other hand, by setting it to 3D or more, a sufficiently large chip pocket can be secured.

  On the other hand, when the predetermined width W is set to be larger than 4D with respect to the diameter D of the tool body 2, the range of the taper portion 10 becomes too wide and the tool rigidity is lowered. Tool rigidity can be ensured by setting it to 4D or less with respect to D.

  Further, the taper portion 10 has a change amount δ of the thickness of the web 9 from the tip end of the tool body 2 toward the end portion P, that is, the thickness T of the web 9 at the tip end of the tool body 2 and the web 9 at the end portion Pt. The difference (δ = T−Tp) from the thickness Tp is set to 0.02D (that is, δ = 0.1 mm in the present embodiment) with respect to the diameter D of the tool body 2.

  Here, the variation amount δ of the thickness of the web 9 is not limited to 0.02D with respect to the diameter D of the tool body 2 as in the present embodiment, but with respect to the diameter D of the tool body 2. It is desirable to set it to 0.02D or less.

  That is, by setting the amount of change δ in the thickness of the web 9 to 0.02D or less with respect to the diameter D of the tool body 2, the diameter 9 of the tool body 2 is set to be larger than 0.02D. In comparison, tool rigidity can be ensured and breakage can be prevented.

  Note that the thickness of the web 9 is constant at Tp on the rear end side of the tool body 2 with respect to the terminal end portion Pt of the tapered portion 10.

  Next, with reference to FIG. 4, an endurance test performed using the drill 1 configured as described above will be described. The durability test is a test for measuring the total number of holes that can be continuously processed when a hole is formed in a workpiece under predetermined cutting conditions.

  The detailed specifications of the durability test are as follows: work piece: JIS-S50C, cutting fluid: water-soluble cutting fluid, cutting speed: 20 m / min, feed rate: 0.12 mm / rev, machining depth: 120 mm (blind hole ), Processing method: non-step processing.

  Further, in the durability test, only the radius R of the groove bottom portion 4a is different from the drill 1 described in the present embodiment (hereinafter referred to as "the product 1 of the present invention"), and the radius R is different. Three types of drills set to 6D (ie, R = 30 mm), 1D (ie, R = 5 mm), and 0.6D (ie, R = 3 mm) with respect to the diameter D of the tool body 2 (hereinafter, “ The present invention product 2 ”,“ modified product 1 ”and“ modified product 2 ”) and a second wall surface portion 4c corresponding to the drill 1 are formed in an arc shape continuously to the groove bottom portion 4a and the groove bottom portion. This was performed using a drill (hereinafter referred to as “conventional product”) in which the radius R of 4a was set to 0.3D (that is, R = 1.5 mm) with respect to the diameter D of the tool body 2.

  FIG. 4 is a graph showing test results of the durability test, and shows the total number of holes that can be processed continuously in the five types of drills described above. In addition, in FIG. 4, the test result of each 2 times performed about five types of drill mentioned above is shown, and in the test result of each drill, the upper stage shows the test result of the 1st time, and the lower stage shows the test result of the 2nd time. , Respectively.

  As shown in FIG. 4, according to the results of the durability test, the product 1 of the present invention was able to increase the total number of holes that can be processed continuously by about 20 times compared to the conventional product. Specifically, the conventional product can no longer be processed (broken) when the number of processed holes reaches about 20, whereas the product 1 of the present invention continues processing until the number of processed holes reaches about 400. Could be done.

  This is because in the conventional product, the wall surface portion corresponding to the second wall surface portion 4c of the product 1 of the present invention is formed in an arc shape continuously to the groove bottom portion, so that a sufficient chip pocket cannot be secured. In the product 1 of the present invention, since the second wall surface portion 4c is formed in a straight line and the first wall surface portion 4b and the second wall surface portion 4c are configured in parallel with each other, the chip pocket can be enlarged. In addition, since the second wall surface portion 4c is formed in a straight line and the first wall surface portion 4b and the second wall surface portion 4c are formed in parallel to each other, the chip pocket is enlarged, so that the tool cross-sectional area is excessively reduced. This is considered to be because the rigidity of the tool could be secured.

  In addition, the products 1 and 2 of the present invention were able to increase the total number of holes that could be processed continuously, compared to the conventional product and the modified products 1 and 2. This is because the radius R of the groove bottom portion 4a is smaller in the conventional product and the modified products 1 and 2 than in the products 1 and 2 of the present invention, so that the chips are likely to curl to the opposite side to the rotation direction of the tool body 2. While the chip discharge resistance and cutting resistance increase, the products 1 and 2 of the present invention have a larger radius R of the groove bottom 4a than the conventional products and the modified products 1 and 2. It is considered that the chips near the groove bottom portion 4a can be smoothly discharged along the rotation direction of the tool body 2 and the chip discharge resistance and cutting resistance can be suppressed. For this reason, it is desirable to set the radius R of the groove bottom 4a to 2D or more with respect to the diameter D of the tool body 2.

  As described above, according to the drill 1 in the present embodiment, the groove bottom 4a of the chip discharge groove 4 is formed in an arc shape that curves in the direction of the axis O in a cross-sectional view perpendicular to the direction of the axis O. Since the radius R is set to 2D with respect to the diameter D of the tool body 2, chips near the groove bottom 4a can be discharged smoothly, and chip discharge resistance and cutting resistance are suppressed. can do. As a result, by suppressing the chip discharge resistance and cutting resistance, it is possible to increase the tool life while improving the chip discharge performance.

  Further, according to the drill 1 in the present embodiment, the chip discharge groove 4 has the first wall surface portion 4b and the second wall surface portion 4c formed in a straight line shape in a cross-sectional view perpendicular to the direction of the axis O, respectively. Since the 1st wall surface part 4b and the 2nd wall surface part 4c are comprised in parallel with each other, tool rigidity can be ensured, aiming at expansion of a chip pocket.

  That is, when trying to expand the chip pocket, it is necessary to reduce the tool cross-sectional area, and accordingly, the tool rigidity is reduced, while when trying to secure the tool rigidity, it is necessary to increase the tool cross-sectional area. As a result, the chip pocket cannot be secured sufficiently, and it has been difficult to achieve both expansion of the chip pocket and tool rigidity.

  On the other hand, according to the drill 1 in the present embodiment, the first wall surface portion 4b and the second wall surface portion 4c are respectively formed in a straight line shape in a cross-sectional view perpendicular to the direction of the axis O, and the first wall surface portion 4b. And the second wall surface portion 4c are configured to be parallel to each other, so that the chip pocket can be enlarged, and the first wall surface portion 4b and the second wall surface portion 4c are respectively formed in a straight line and the first wall surface portion. Since the chip pocket is enlarged by configuring 4b and the second wall surface portion 4c in parallel with each other, the tool rigidity can be ensured without reducing the tool cross-sectional area too much.

  Here, the groove length L of the chip discharge groove 4 is not limited to 30D with respect to the diameter D of the tool body 2 as in the drill 1 in the present embodiment, but with respect to the diameter D of the tool body 2. It is desirable to set it to 20D or more.

  That is, by setting the groove length L to 20D or more with respect to the diameter D of the tool body 2, it is difficult to discharge chips as compared with the case where the diameter D of the tool body 2 is smaller than 20D. In the processing of deep holes, the effect of improving the chip discharge performance can be effectively exhibited.

  Furthermore, if such an effect can be effectively exhibited, even in deep hole machining, there is no need to perform stepwise drilling while repeating feed and return, so-called step machining is performed, and the machining efficiency is improved. be able to.

  The present invention has been described above based on the embodiments, but the present invention is not limited to the above embodiments, and various improvements and modifications can be made without departing from the spirit of the present invention. It can be easily guessed.

  For example, the numerical values given in the above embodiment are merely examples, and other numerical values can naturally be adopted.

  Moreover, although the said embodiment demonstrated the case where the drill 1 was comprised from a cemented carbide alloy, it is not necessarily restricted to this, For example, you may comprise from high-speed tool steel etc.

  Moreover, although the said embodiment demonstrated the case where the chip discharge | emission groove | channel 4 was twisted around the shaft center O and formed (spiral), it is not necessarily restricted to this, A straight line along the shaft center O direction You may form in a shape.

  Moreover, although the said embodiment demonstrated the case where the two cutting blades 3 were provided, it is not necessarily restricted to this, For example, it comprises and comprises the cutting blade 3 of 1 sheet or 3 sheets or more. Also good.

It is a front view of the drill in one embodiment of the present invention. FIG. 2 is an enlarged cross-sectional view of a drill perpendicular to the direction of the axis O in line II-II in FIG. 1. It is the expanded sectional view which looked at the rotation locus of the groove bottom of a chip discharge groove. It is a graph which shows the test result of an endurance test.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drill 2 Tool main body 3 Cutting edge 4 Chip discharge groove 4a Groove bottom part 4b 1st wall surface part 4c 2nd wall surface part 9 Web 10 Taper part D Tool body diameter L Groove length O Axis center R Groove bottom radius T Tool body radius Web thickness at tip W Predetermined width α Twist angle

Claims (6)

A tool body that rotates about an axis, a cutting edge provided at the tip of the tool body, a rake face of the cutting edge, and a recess formed in the outer peripheral surface of the tool body, the rear end from the tip of the tool body In a drill with a chip discharge groove extending toward the side,
The chip discharge groove includes a groove bottom portion constituting a groove bottom,
The groove bottom portion is formed in an arc shape that curves in the axial direction in a cross-sectional view perpendicular to the axial direction, and the radius thereof is set to 2D or more with respect to the diameter D of the tool body. A drill characterized by that. The chip discharge groove is provided continuously with the groove bottom portion and forms a wall surface facing the rotation direction of the tool body, and is provided continuously with the groove bottom portion and on the rear side in the rotation direction of the tool body. A second wall surface portion that constitutes a facing wall surface,
In the cross-sectional view perpendicular to the axial direction, the first wall surface portion and the second wall surface portion are each formed in a substantially linear shape, and the first wall surface portion and the second wall surface portion are configured to be substantially parallel to each other. The drill according to claim 1.   The drill according to claim 1 or 2, wherein a groove length of the chip discharge groove is set to 20D or more with respect to a diameter D of the tool body. A taper portion configured such that the thickness of the web formed by the groove bottom of the chip discharge groove gradually decreases from the front end side to the rear end side of the tool body;
The tapered portion is provided with a predetermined width along the axial direction from the tip of the tool body, and the predetermined width is set within a range of 3D or more and 4D or less with respect to the diameter D of the tool body, The amount of change in the thickness of the web from the front end to the rear end side of the tool body at the tapered portion is set to 0.02D or less with respect to the diameter D of the tool body. The drill according to any one of 3 above.   The thickness of the web at the tip of the tool body is set in a range of 0.35D or more and 0.45D or less with respect to the diameter D of the tool body. The drill of crab.   6. The chip discharge groove is formed by being twisted around the axis, and the twist angle thereof is set in a range of 35 degrees or more and 45 degrees or less. The drill described.

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