JP2013198977A - Drilling tool - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a highly practical drilling tool capable of greatly improving breaking resistance and hole position accuracy compared with a conventional PCB drill.SOLUTION: A drilling tool is configured so that, at the outer periphery of a tool body 1, a first chip exhaust groove 2a including three twist regions having predetermined twist angles and a second chip exhaust groove 2b including two twist regions having predetermined twist angles are arranged, and in the midway part of one chip exhaust groove, the other is continuously disposed, and two grooves, a parallel running transfer part, and a parallel traveling part are sequentially arranged from the tip side. The twist angles of the parallel traveling parts of both chip exhaust grooves are set larger than those of the two grooves, and the changing position of the twist angle located at the most tool tip side is set at a position of 1/2 or smaller than the groove length of the chip exhaust groove formed from the tool tip to a predetermined position of the base end side of the tool body 1 larger by 1.5 times or more than a tool diameter.

Description

  The present invention relates to a drilling tool.

  In recent years, drills for drilling printed wiring boards (PCBs) disclosed in Patent Document 1 (hereinafter referred to as PCB drills) have been reduced in diameter, and aspect ratios (represented by groove length / diameter). Therefore, further improvement in breakage resistance and hole position accuracy is demanded at present.

JP 2012-11489 A

  The present invention has been made in view of the current situation as described above, and provides a drilling tool excellent in practicality that can greatly improve the breakage resistance and the hole position accuracy as compared with conventional PCB drills. is there.

  The gist of the present invention will be described with reference to the accompanying drawings.

  Two cutting edges are provided at the tip of the tool body 1, and two spiral first chip discharge grooves 2 a and a second chip discharge groove from the tool tip to the base end side on the outer periphery of the tool body 1. 2b, the first chip discharge groove 2a has three twist regions each having a predetermined twist angle, and the second chip discharge groove 2b has two twist regions each having a predetermined twist angle. Of these two chip discharge grooves 2a, 2b, one of the chip discharge grooves 2a, 2b is connected to the middle of the other chip discharge groove 2a, 2b, and the first chip discharge At least one of the grooves 2a or the second chip discharge groove 2b is formed up to a predetermined position on the base end side of the tool body 1, and the first chip discharge from the tool front end side. Twist angle of groove 2a and second chip discharge groove 2b Two equal groove portions, a parallel running transition portion in which the twist angles of the first chip discharge groove 2a and the second chip discharge groove 2b are made different from each other, and the first chip discharge groove provided in a row 2a and the second chip discharge groove 2b are equal to each other, and a drilling tool is provided in which a parallel running portion is provided in order to make the twist angle parallel to each other, the first chip discharge groove 2a and the second chip discharge groove 2b. The twist angle of the parallel running part of the second chip discharge groove 2b is set to an angle larger than the twist angle of the two groove parts, and the change position of the twist angle located closest to the tool tip side is the tool diameter from the tool tip. The present invention relates to a drilling tool characterized in that it is provided at a position not more than 1/2 times the groove length of a chip discharge groove formed to a predetermined position on the base end side of the tool body 1 at least 1.5 times. is there.

  The drilling tool according to claim 1, wherein the twist angle of the parallel running transition portion in the first chip discharge groove 2a is larger than the twist angle of the two groove portions. Is.

  Further, in the drilling tool according to any one of claims 1 and 2, a difference between a twist angle of the parallel running transition portion of the first chip discharge groove 2a and a twist angle of the two groove portions is 3 ° or more. The present invention relates to a drilling tool characterized by being set to 25 ° or less.

  Further, in the drilling tool according to any one of claims 1 and 2, the difference between the twist angle of the parallel running transition portion and the twist angle of the two groove portions of the first chip discharge groove 2a is 5 ° or more. The present invention relates to a drilling tool characterized by being set to 15 ° or less.

  Moreover, the drilling tool of any one of Claims 1-4 WHEREIN: The twist angle of 2 groove parts of said 1st chip discharge groove 2a and said 2nd chip discharge groove 2b is 30 degrees or more and 50 It relates to a drilling tool characterized in that it is set to ° or less.

  Further, in the drilling tool according to any one of claims 1 to 5, the twist angle of the parallel running part of the first chip discharge groove 2a and the second chip discharge groove 2b is the two groove part. The present invention relates to a drilling tool characterized in that it is set at an angle that is 2 ° or more and 20 ° or less larger than the twist angle.

  Moreover, the drilling tool of any one of Claims 1-6 WHEREIN: The axial direction groove width of the parallel groove in the starting end position of the said parallel running part is in the change position of the twist angle located in the tool front end side most. The present invention relates to a drilling tool characterized by being set to 1.1 times or more and 1.9 times or less of the axial groove width.

  Moreover, the drilling tool of any one of Claims 1-7 WHEREIN: The groove length of one chip discharge groove is the groove length of the other chip discharge groove among the two chip discharge grooves. % To 95% or less, which relates to a drilling tool.

  Moreover, the drilling tool of any one of Claims 1-8 WHEREIN: The narrow angle at which the first chip discharge groove 2a and the second chip discharge groove 2b rise is larger than 90 ° and 180 °. The present invention relates to a drilling tool characterized by being set as follows.

  Since the present invention is configured as described above, it is a drilling tool excellent in practicality that can greatly improve the breakage resistance and the hole position accuracy as compared with the conventional PCB drill.

It is a tool axis direction front view of Example 1, and a schematic explanatory view of a main part. It is a general | schematic expanded view which shows the outline | summary of the 1st chip discharge groove | channel and the 2nd chip discharge groove | channel of Example 1. FIG. It is a general | schematic expanded view which shows the outline | summary of the 1st chip discharge groove | channel and the 2nd chip discharge groove | channel of Example 2. FIG. It is a general | schematic expansion | deployment figure which shows the outline | summary of the 1st chip discharge groove and 2nd chip discharge groove of another example. It is a table | surface which shows an experimental condition and an experimental result. It is a table | surface which shows an experimental condition and an experimental result. It is a table | surface which shows an experimental condition and an experimental result.

  An embodiment of the present invention which is considered to be suitable will be briefly described with reference to the drawings showing the operation of the present invention.

  Compared to the case where the two chip discharge grooves are provided independently without providing the two chip discharge grooves by providing a parallel running part for running the first chip discharge groove 2a and the second chip discharge groove 2b side by side. In addition, the groove volume can be reduced to ensure rigidity.

  Furthermore, the first chip discharge groove 2a and the second chip discharge groove 2b are configured such that one of the twist angles is changed to two steps and the other twist angle is changed to three steps so as to connect both. In addition, it is possible to minimize the number of changes in the twist angle of the chip discharge groove while minimizing the parallel running transition part (distance of the parallel running transition part in the tool axis direction). The running portion (distance of the parallel running portion in the tool axis direction) can be increased by that much, and therefore the breakage resistance and the hole position accuracy can be greatly improved.

  A first embodiment of the present invention will be described with reference to the drawings.

  In the first embodiment, two cutting edges are provided at the tip of the tool body 1, and two spiral first chip discharge grooves 2 a and a second one extending from the tool tip to the base side on the outer periphery of the tool body 1. The first chip discharge groove 2a includes three twist regions each having a predetermined twist angle, and the second chip discharge groove 2b has a predetermined twist angle. Of the chip discharge grooves 2a and 2b, one of the chip discharge grooves 2a and 2b is continuously provided in the middle of the other chip discharge groove 2a and 2b, At least one of the chip discharge groove 2a and the second chip discharge groove 2b is formed up to a predetermined position on the base end side of the tool body 1, and the first chip side is formed from the tool tip side. Screws for the chip discharge groove 2a and the second chip discharge groove 2b Two groove portions having equal angles, the parallel running transition portion in which the twist angles of the first chip discharge groove 2a and the second chip discharge groove 2b are made different from each other, and the first chip that are connected in series A drilling tool in which parallel running portions for making the twist angles of the discharge groove 2a and the second chip discharge groove 2b equal to each other and running them in parallel are sequentially provided, and the first chip discharge groove 2a and The twist angle of the parallel running portion of the second chip discharge groove 2b is set to an angle larger than the twist angle of the two groove portions, and the change position of the twist angle located closest to the tool tip is determined from the tool tip to the tool. It is provided at a position not less than ½ of the total length of the chip discharge groove formed to a predetermined position on the base end side of the tool body 1 at least 1.5 times the diameter.

  In the first embodiment, a tool main body 1 having a spiral chip discharge groove provided on the outer periphery, a shank taper portion continuously provided on the tool main body 1 and gradually increasing in diameter toward the tool base end side, and connected to the shank taper portion. It is a PCB drill which is provided and has a shank portion having a diameter of 3.175 mm. The tool body 1 is formed of a cemented carbide member, and the shank portion is formed of a stainless steel member, and both are joined. Although the shank taper portion and the shank portion are not shown, the shank taper portion is generally set to 20 ° or more and 90 ° or less, and is formed at 30 ° in the first embodiment.

  In the first embodiment, as shown in FIG. 1, a first chip discharge groove 2 a and a second chip discharge groove 2 b are provided on the outer periphery of the tool body 1, and the two chips are provided. The discharge grooves are provided at a split angle of 180 ° with respect to the center of rotation when viewed from the tip of the tool. The rake face of the first chip discharge groove 2a and the second chip discharge groove 2b and the tip flank of the tool body 1 are provided. Is a two-edged, two-grooved drill in which cutting edges 4 are provided integrally with the tool body 1 at the intersecting ridges. That is, the cutting edge 4 is also provided at a split angle of 180 ° with respect to the center of rotation in the tool tip view. Specifically, it is a PCB drill having a tool aspect ratio of 15 or more and a tool diameter of 0.7 mm or less.

  In the first embodiment, the second chip discharge groove 2b is formed up to a predetermined position on the base end side of the tool body 1 (a position before the shank taper portion), and the second chip discharge groove 2b is formed in the second chip discharge groove 2b. The first chip discharge groove 2a that is continuously provided and runs in parallel is formed shorter than the second chip discharge groove 2b. That is, the first chip discharge groove 2a and the second chip discharge groove 2b are arranged at different twist angles, and a part of both overlaps, and then the deepest point of each groove is a predetermined distance with the same twist angle. It is set as the structure (parallel running groove) in which two grooves run in parallel in a separated state. In addition, it is good also as a structure which reverses the groove length of two chip discharge grooves, and forms the 1st chip discharge groove 2a longer than the 2nd chip discharge groove 2b.

  The reason why the first chip discharge groove 2a is connected to the middle part of the second chip discharge groove 2b as described above is as follows.

  Causes of PCB drill breakage include: (a) hole bending due to lack of drill stiffness (strength), (b) insufficient groove volume of chip discharge groove, small helix angle (chip rising action in chip discharge groove) And the like, and (c) hole bending due to wear, chip discharge deterioration, and the like.

  In any case, as the machining depth becomes deeper than the diameter of the machining hole, the cutting resistance increases due to the above (a) to (c), and the strength of the drill becomes unbearable, leading to breakage. Therefore, securing the rigidity and reducing the cutting resistance (improving the discharge performance and reducing the contact area with the inner wall of the hole) are issues to improve the breakage resistance of the drill. However, ensuring the rigidity and reducing the cutting resistance There is a trade-off relationship.

  Further, the more the PCB drill has a higher rigidity, the more difficult it is to bend, and the hole position accuracy tends to improve. However, the chip discharge performance deteriorates, the hole inner wall roughness deteriorates, the chip remaining around the hole due to the lack of good chip discharge performance, or the deformation of the backing plate associated therewith. The straight advanceability when entering the plate may deteriorate and the hole position accuracy may deteriorate.

  Thus, by making the first chip discharge groove 2a and the second chip discharge groove 2b as described above into a continuous shape (two-blade groove continuous shape), good cutting performance can be achieved on the tool tip side. It is possible to provide a discharge property, ensure rigidity on the tool base end side (base side), and improve breakage resistance and hole position accuracy as compared with the conventional 2-blade 2-groove shape.

  Furthermore, in Example 1, it is not only simply the above-mentioned two-blade groove continuous shape, but also by devising the change step number of the twist angle of the first chip discharge groove 2a and the second chip discharge groove 2b, The distance of the parallel running transition part in the tool axis direction is shortened, and the distance of the parallel running part contributing to the rigidity improvement is made as long as possible so that the rigidity of the drill can be improved and the hole position accuracy can be improved.

  That is, in Example 1, the distance between the parallel running transition portions in the tool axis direction is made as much as possible by changing the twist angles of both the first chip discharging groove 2a and the second chip discharging groove 2b in the middle. It is connected continuously so as to be shorter. Specifically, as the second chip discharge groove 2b, the twist angle is changed in two steps (the twist angle is changed once so as to have two twist areas) and the first chip discharge groove 2a is formed. The twist angle is changed in three stages (the twist angle is changed twice so as to have three twist regions), and both are connected in the middle of the tool.

  Specifically, in the first embodiment, as illustrated in FIG. 2, the twist angle θ1 of the tip portion (two groove portions) of the first chip discharge groove 2a and the second chip discharge groove 2b is the same angle. The second chip discharge groove 2b is set to the twist angle θ2 from the first twist angle change position P1, and the first chip discharge groove 2a is set to the twist angle from the second twist angle change position P2. Increasing θ3 is connected to the second chip discharge groove 2b, and after the connection, the first chip discharge groove 2a is set to the twist angle θ2 from the third twist angle change position P3. Both are configured to run in parallel. The torsion angle change position is the first torsion angle change position (the torsion angle change position located closest to the tool tip side) and the second torsion angle change position in order from the tool tip side, regardless of the chip discharge groove. This is referred to as a third twist angle change position. Further, the twist angle θ3 of the parallel running transition portion in the first chip discharge groove 2a is referred to as a continuous angle.

  Further, in the drawing, the two-groove portion means that the first chip discharge angle change in the tool axis direction is equal in the twist angle of the first chip discharge groove 2a and the second chip discharge groove 2b from the tool tip. Up to the position P1, the parallel running transition part is from the first twist angle change position P1 to the third twist angle change position P3, and the parallel run part is from the third twist angle change position P3 to the tool proximal end side. It refers to a section in which the first chip discharge groove 2a and the second chip discharge groove 2b are formed in parallel. In the first embodiment, the first twist angle change position P1 is a chip discharge groove (second shape) formed from the tip of the tool to a predetermined position on the base end side of the tool body 1 at least 1.5 times the tool diameter. It is provided at a position of 1/2 or less of the groove length of the chip discharge groove 2b). If the first twist angle changing position P1 is provided at a position less than 1.5 times the tool diameter from the tool tip, it is highly likely that the tool will be polished to the changing position P1 at the time of re-polishing, making it difficult to obtain a suitable blade shape. If it is provided at a position closer to the base end side than 1/2 of the groove length of the second chip discharge groove 2b from the tip of the tool, the two groove portions become too long, the groove volume becomes large, the rigidity of the tool deteriorates, and the hole Positional accuracy deteriorates and the possibility of breakage increases. As described above, in the case where the groove lengths of the two chip discharge grooves are reversed, the first twist angle change position P1 is not less than 1.5 times the tool diameter from the tool tip. It is provided at a position that is 1/2 or less of the groove length of the waste discharge groove 2a.

  More specifically, in Example 1, the twist angle θ1 of the two groove portions of the first chip discharge groove 2a and the second chip discharge groove 2b is set to 30 ° to 50 ° (same angle). The difference between the twist angle θ3 (consecutive angle) of the parallel running transition part of the first chip discharge groove 2a and the twist angle θ1 of the two groove parts is set to 3 ° or more and 25 ° or less, and the second chip discharge groove 2 b is arranged in parallel, and the torsion angle θ2 of the parallel running part is set to an angle (same angle) that is 2 ° or more and 20 ° or less larger than the torsion angle θ1 of the two groove parts.

  When the twist angle of the two groove portions is smaller than 30 °, the chip dischargeability is deteriorated, the inner wall roughness is easily deteriorated, and breakage is easily caused. On the other hand, when the angle exceeds 50 °, the blade angle of the cutting edge (the angle formed by the rake face and the flank face) becomes small, so that the cutting edge tends to be lost, cutting performance deteriorates, and the hole position accuracy and inner wall roughness are reduced. It becomes easy to lead to deterioration. In Example 1, it is set to 45 °.

  Further, in the case of a two-blade, two-groove shape, by setting the two twist angles at the tip portion to be equal, the straightness is good when entering the work material, and good hole position accuracy can be obtained.

  In the conventional general PCB drill, the twist angle of the chip discharge groove is constant from the front end to the base end in consideration of ease of manufacture. However, by changing the torsion angle within the groove length, performance can be improved as compared to a drill with a constant torsion angle. That is, for example, it is possible to improve the chip discharging property by setting a small twist angle in order to prevent winding at the distal end and setting a large twist angle on the base end side accordingly.

  In this way, by changing the twist angle of the chip discharge groove into a plurality of stages, the shape can be optimized for improving the performance. However, as the number of stages of the twist angle increases (for example, the second chip discharge) The configuration in which the twist angle of the groove 2b is changed to three steps and the twist angle of the first chip discharge groove 2a is changed to four steps, and the twist angle of the second chip discharge groove 2b is changed to four steps, Such as a configuration in which the twist angle of the waste discharge groove 2a is changed to 5 steps), and the shape becomes complicated, making the manufacture difficult. Therefore, it is desirable to optimize the shape efficiently with the minimum number of steps.

  By the way, the drill of the shape (parallel connection shape of a groove | channel continuous arrangement | positioning) which parallels after a groove | channel continuous arrangement | sequence is comprised by a 2 groove part, a parallel movement transfer part, and a parallel movement part.

  In the parallel running portion, the chip discharge grooves are overlapped with each other, so that the groove volume can be reduced as compared with the case where the two chip discharge grooves are provided independently, thereby ensuring rigidity. Therefore, the larger the ratio of the parallel running parts within the groove length is set with respect to the ratio of the 2 groove parts (and the parallel running transition part), the harder the drill is bent.

  In the two grooves at the tool tip, two chip discharge grooves are provided independently, and a cutting edge is provided in each chip discharge groove, so that good cutting performance and discharge can be obtained.

  As described above, the parallel running portion can secure rigidity, but the discharge performance may be deteriorated, and it may be easily broken. Therefore, by setting the twist angle of the parallel running portion to be 2 ° or more and 20 ° or less larger than the twist angle of the two groove portions, the discharge property is supplemented and the breakage resistance is improved. Here, if the angle is less than 2 °, it is difficult to obtain a sufficient effect of improving dischargeability. If the angle is larger than 20 °, the rigidity is deteriorated and the drill is easily bent.

  Furthermore, in the parallel running transition portion, there is a section in which two independent chip discharge grooves having different twist angles are provided. In this section, the flow of chips becomes unbalanced, and further, two chip discharge grooves exist independently, so that the groove volume becomes larger than that of the parallel running portion, and the rigidity tends to be unstable. Therefore, the length of the parallel transition portion (distance of the parallel transition portion in the tool axis direction) is preferably as short as possible (one in which the ratio of the parallel transition portions in the groove length is reduced).

  In addition, in order to form a groove-connected parallel running shape with a minimum number of twist angle steps, each twist discharge angle is set to change in two steps in each chip discharge groove. If the position where the angle changes is set to a different position, it is possible to form a parallel running shape with grooves. However, it is more parallel in the tool axis direction if the twist angle of one chip discharge groove is set to change in three steps and the twist angle of the other chip discharge groove is changed in two steps. The distance of the transition part can be shortened to reduce the ratio of the parallel transition part in the groove length, and the drill performance can be further improved.

  Although it is possible to further reduce the distance of the parallel transition portion in the tool axis direction by providing a larger number of twist angle steps, the more the number of changes in the twist angle as described above, the more the manufacturing becomes. It becomes difficult. For this reason, the twist angle of one chip discharge groove is set to be changed in three steps, and the twist angle of the other chip discharge groove is set to be changed in two steps to form a parallel running shape. The performance can be improved with a smaller number of twist angle steps.

  In the first embodiment, as shown in FIG. 2, the twist angle of the second chip discharge groove 2b is changed in two steps (changed from θ1 to θ2 at the position of P1), and the first chip discharge is performed. The twist angle of the groove 2a is changed in three steps (changed from θ1 to P2 to θ3 and from θ3 to P3 to θ2).

  When the continuous angle θ3 is made larger than the twist angle θ1 of the two grooves and the twist angle θ2 of the parallel running part, the chip discharging property at the parallel running part is good and the breakage resistance is good. It becomes. At this time, it is desirable that the difference between θ3 and θ1 be 3 ° or more and 25 ° or less. If the angle is smaller than 3 °, the parallel running transition portion becomes too long and the parallel running portion becomes shorter accordingly, so that the rigidity of the tool is reduced. If the angle is greater than 25 °, the twist angle of the parallel running transition portion becomes too large, so that the torsional rigidity at the parallel running transition portion is lowered and easily broken. More preferably, the difference between θ3 and θ1 is 5 ° or more and 15 ° or less.

  Further, as in another example illustrated in FIG. 4, when the parallel running is performed with the continuous angle θ3 smaller than the twist angle θ1 of the two grooves and the twist angle θ2 of the parallel running part, in the parallel running transition part The torsional rigidity is enhanced and the hole position accuracy is improved. At this time, it is desirable that the difference between θ3 and θ1 be 3 ° or more and 25 ° or less. If the angle is smaller than 3 °, the parallel running transition portion becomes too long and the parallel running portion becomes shorter accordingly, so that the rigidity of the tool is reduced. If the angle is greater than 25 °, the discharge performance at the parallel running transition portion is reduced and breakage tends to occur. More preferably, the difference between θ3 and θ1 is 5 ° or more and 15 ° or less.

  In the first embodiment, θ3 is made larger than θ1 and θ2, and the parallel running is performed. Specifically, θ1 is set to 45 °, θ2 is set to 50 °, and θ3 is set to 55 °. That is, the difference between θ3 and θ1 is 10 °. In another example of FIG. 4, θ1 is set to 45 °, θ2 is set to 50 °, and θ3 is set to 35 ° as a configuration in which θ3 is made smaller than θ1 and θ2 to run in parallel. That is, the difference between θ3 and θ1 is 10 °.

  The twist angles θ1 to θ3 are selected based on the processing characteristics of the printed wiring board material and the required quality of the product, and are applied to drills with an aspect ratio of 15 or more, which are generally difficult to drill. Especially effective.

  Further, the axial groove width of the parallel groove at the starting end position of the parallel running portion is 1.1 times or more and 1.9 times or less of the axial groove width at the change position of the torsion angle located closest to the tool tip side. Is set. In Example 1, the axial groove width B of the parallel running groove at the start end position of the parallel running part is the connecting point (the intersection of the groove ridge lines of the first chip discharging groove 2a and the second chip discharging groove 2b). ) It is set to be 1.1 times or more and 1.9 times or less of the axial groove width A of the first twist angle changing position P1 on the front side. The starting end position Q of the parallel running portion is the third twist angle change position P3. The axial groove width B of the parallel running groove at the starting end position Q of the parallel running portion refers to the groove width measured on the proximal side in the tool axis direction including the starting end position of the parallel running portion. Specifically, in Example 1, the groove width in the axial direction measured from the starting end position of the parallel running portion intersecting the groove ridge line of the second chip discharge groove 2b toward the base end side in the tool axial direction. Say B. When the axial groove width B of the parallel groove at the starting end position Q of the parallel running portion is less than 1.1 times the axial groove width A at the first twist angle change position P1 located closest to the tool tip, When the groove volume is too small, it is difficult to obtain a smooth chip discharging property. When the groove volume is larger than 1.9 times, it is difficult to ensure the rigidity of the drill because the groove volume is large. In Example 1, the axial groove width B of the parallel groove at the starting end position Q of the parallel running part is 1.5 times the axial groove width A of the first twist angle changing position P1 before the connection point. Is set.

  In addition, the length of one of the two chip discharge grooves is set to 50% or more and 95% or less of the length of the other chip discharge groove. In Example 1, the groove length of the first chip discharge groove 2a is shorter than the groove length of the second chip discharge groove 2b formed up to the base end of the tool body 1, and the second chip discharge groove 2b. The groove length is set to be 50% or more and 95% or less. The two groove lengths may be the same length, but by using different lengths, rigidity can be secured at the tool base end (base) that tends to be the starting point of breakage, and breakage resistance is further improved. Can do. When the groove length of the first chip discharge groove 2a is less than 50% of the groove length of the second chip discharge groove 2b, from the intermediate portion of the groove, which is important for discharging chips to the outside of the substrate, from the base end Therefore, if the length is longer than 95%, the difference from the groove length of the second chip discharge groove 2b is reduced, and the rigidity at the tool base end is increased. It becomes difficult to secure. In Example 1, the groove length of the first chip discharge groove 2a is set to 90% of the groove length of the second chip discharge groove 2b. In the other example shown in FIG. 4, the groove length of the second chip discharge groove 2 b is shorter than the groove length of the first chip discharge groove 2 a formed up to the base end of the tool body 1. Specifically, the groove length of the second chip discharge groove 2b is set to 90% of the groove length of the first chip discharge groove 2a.

  Further, in the first embodiment, the first chip discharge in the respective cross sections perpendicular to the tool axis including the end points at the ends of the first chip discharge groove 2a and the second chip discharge groove 2b. A first line connecting one of the groove 2a and the second chip discharge groove 2b and the rotation axis of the tool, and a second line connecting the other edge and the rotation axis of the tool. When a line is projected onto the same axis perpendicular projection plane in the axial view of the tool, the narrow angle (so-called cut-off narrow angle) formed by the first line and the second line on this projection plane is 90 °. More specifically, the angle is set to 180 ° or less (the narrowing angle is the rotational phase difference (angle difference) between the rising end point of the first chip discharge groove 2a and the rising end point of the second chip discharge groove 2b. Represented by :).

  When the cut-off narrow angle is 90 ° or less, the chip discharge direction is deviated, so that unbalanced discharge occurs on the tool base end side, which may cause sudden hole bending.

  Therefore, by making the narrow angle of the first chip discharge groove 2a and the second chip discharge groove 2b greater than 90 ° and 180 ° or less, uneven discharge of chips can be prevented, and the balance Chips can be discharged well.

  Further, the tool body 1 may be coated with a lubricating film such as an amorphous carbon film. Coating with a lubricious coating such as an amorphous carbon coating improves chip evacuation and enables highly accurate drilling utilizing the shape with excellent rigidity.

  Moreover, it is good also as a structure which provides a 2nd picking surface between the chip discharge groove | channel and the land part 3. FIG. In this case, since the contact area between the outer periphery of the land portion and the inner wall of the hole can be reduced during drilling, cutting resistance at the tool tip can be reduced.

  Since Example 1 is configured as described above, a plurality of chip discharge grooves are continuously provided by providing a parallel running section that causes the first chip discharge groove 2a and the second chip discharge groove 2b to run side by side. As compared with the case where each of them is provided independently, the groove volume can be reduced and the rigidity can be ensured. Of course, the second chip discharge groove 2b has two twist angles, By changing the torsion angle of one chip discharge groove 2a in three stages and connecting them in parallel, the parallel movement in the tool axis direction is minimized while minimizing the number of changes in the torsion angle of the chip discharge groove. It is possible to shorten the distance of the part as much as possible, and it is possible to lengthen the parallel running part that contributes to the improvement of rigidity, thereby greatly improving the breakage resistance and the hole position accuracy. .

  A second embodiment of the present invention will be described with reference to the drawings.

  In the second embodiment, as shown in FIG. 3, the first chip discharge groove 2a and the second chip discharge groove 2b have their twist angles θ1 set to the same angle. The chip discharge groove 2a is continuously connected to the second chip discharge groove 2b by increasing the twist angle θ3 (consecutive angle) from the first twist angle changing position P1. By setting the waste discharge groove 2a to the twist angle θ2 from the third twist angle change position P3, the two are moved in parallel.

  The rest is the same as in Example 1.

  An experimental example supporting the effects of Examples 1 and 2 will be described.

  FIGS. 5-7 is a table | surface which shows the experimental condition and experimental result which changed the form of the two chip | tip discharge groove | channels of a drill, and evaluated fracture resistance and hole position accuracy.

  The drill used in the experiment of FIG. 5 has a tool diameter of 0.1 mm, a groove length (longer one of the two chip discharge grooves) of 1.8 mm, and an aspect ratio of 18. In FIG. 5, in the conventional example 1 and the prior art example 2, for comparison with the experimental example, the two chip discharge grooves are expressed as a first chip discharge groove and a second chip discharge groove ( The same applies to FIGS. 6 and 7). However, in the conventional example 1, the twist angle of one chip discharge groove (first chip discharge groove) is changed in three stages to change the other chip discharge groove (second chip discharge groove). In the conventional example 2 in which the twist angle of the (scrap discharge groove) is not changed (1 stage, remains 45 °), the conventional example 2 has two chip discharge grooves (first chip discharge groove and second chip discharge groove). Each example is changed in two stages. In Experimental Example 1, Experimental Example 2 (Example 1), and Experimental Example 3 (another example), the twist angle of the first chip discharge groove is changed to three stages and the second chip discharge groove is changed to two stages. In Experimental Example 1 and Experimental Example 2, the continuous angle θ3 is made larger than the twist angle θ1 of the two grooves as shown in FIG. 2, and in Experimental Example 3, the continuous angle as shown in FIG. In this example, the angle θ3 is smaller than the twist angle θ1 of the two grooves. The drill material and other shape items (tip angle, web thickness, etc.) are the same. Moreover, the twist angle change position on the most distal end side of each drill is set to 0.35 mm.

  With the above drill, 8 sheets of “BT thickness 0.1 mm (double-sided plate)” as a base material are stacked, an aluminum plate with resin (thickness 0.11 mm) as a backing plate, and a bake plate (thickness 1) 5 mm), drilling experiments were performed at a drill (spindle) rotation speed of 300 krpm, a feed rate of 3.0 m / min, and a spindle lift rate of 50 m / min.

  The fracture life was evaluated by calculating the average value of the number of hits until each drill breaks for each of five specifications. In addition, the hole position accuracy was evaluated by calculating the average + 3σ value of the hole misalignment amount of all the processed holes on the back side of the bottom substrate of each specification 5 pieces (4,000 hits per piece, total 20,000 hits). .

  From FIG. 5, it was confirmed that all of Experimental Examples 1, 2, and 3 were superior in break resistance and hole position accuracy compared to Conventional Examples 1 and 2. Further, it was confirmed that the larger the connecting angle θ3, the better the breakage resistance, and the smaller one, the better the hole position accuracy.

  The drill used in the experiment of FIG. 6 has a tool diameter of 0.3 mm, a groove length of 6.5 mm, and an aspect ratio of 22. Further, Conventional Example 3 is an example in which the twist angle of one chip discharge groove is not changed and the other chip discharge groove is changed to three stages, and Conventional Example 4 is that two chip discharge grooves are changed to two stages respectively. Example 4, Experimental Example 4 and Experimental Example 5 are examples in which the twist angle of the first chip discharge groove is changed to three steps and the second chip discharge groove is changed to two steps. As shown in FIG. 2, the continuous angle θ3 is made larger than the twist angle θ1 of the two grooves, and in Experimental Example 5, the continuous angle θ3 is made smaller than the twist angle θ1 of the two grooves as shown in FIG. . The drill material and other shape items (tip angle, web thickness, etc.) are the same. Further, the twist angle change position on the most distal end side of each drill is 1.0 mm.

  Using the drills above, three “FR-4 halogen-free material thickness 1.6 mm (six-layer plate)” as a base material is stacked, an aluminum plate (thickness 0.15 mm) as a backing plate, and a bake plate as a discard plate (Thickness 1.5 mm) was used, and a drilling experiment was performed at a drill (spindle) rotation speed of 120 krpm, a feed rate of 2.1 m / min, and a spindle ascending speed of 25.4 m / min.

  The breakage life was evaluated by calculating the breakage rate of drills that were broken at a setting of 10,000 hits for each of the 10 specifications and broken before 10,000 hits. In addition, the hole position accuracy was evaluated by calculating the average + 3σ value of the hole misalignment amount of all the processed holes on the back side of the bottom substrate of each specification 10 pieces (2,000 hits per piece, total 20,000 hits). .

  From FIG. 6, it was confirmed that the experimental examples 4 and 5 were superior in the fracture resistance and the hole position accuracy to the conventional examples 3 and 4. Further, it was confirmed that the larger the connecting angle θ3, the better the breakage resistance, and the smaller one, the better the hole position accuracy.

  The drill used in the experiment of FIG. 7 has a tool diameter of 0.65 mm, a groove length of 10 mm, and an aspect ratio of 15. Conventional example 5 is an example in which the twist angle of one chip discharge groove is not changed and the other chip discharge groove is changed to three stages, and conventional example 6 is that two chip discharge grooves are changed to two stages, respectively. Example 6 and Experiment 7 are examples in which the twist angle of the first chip discharge groove is changed to three steps and the second chip discharge groove is changed to two steps. As shown in FIG. 2, the continuous angle θ3 is made larger than the twist angle θ1 of the two grooves, and in Experimental Example 7, the continuous angle θ3 is made smaller than the twist angle θ1 of the two grooves as shown in FIG. . The drill material and other shape items (tip angle, web thickness, etc.) are the same. Moreover, the twist angle change position on the most distal end side of each drill is set to 1.2 mm.

  Using the above drill, 5 sheets of “FR-4 halogen-free material thickness 1.6 mm (6-layer plate)” as a base material are stacked, an aluminum plate (thickness 0.15 mm) as a backing plate, and a bake plate as a discard plate (Thickness 1.5 mm) was used, and a drilling experiment was performed at a drill (spindle) rotation speed of 70 krpm, a feed rate of 2.1 m / min, and a spindle lift rate of 25.4 m / min.

  The breakage life was evaluated by calculating the breakage rate of drills that were broken at a setting of 10,000 hits for each of the 10 specifications and broken before 10,000 hits. In addition, the hole position accuracy was evaluated by calculating the average + 3σ value of the hole misalignment amount of all the processed holes on the back side of the bottom substrate of each specification 10 pieces (2,000 hits per piece, total 20,000 hits). .

  From FIG. 7, it was confirmed that the experimental examples 6 and 7 were superior in the fracture resistance and the hole position accuracy to the conventional examples 5 and 6. Further, it was confirmed that the larger the connecting angle θ3, the better the breakage resistance, and the smaller one, the better the hole position accuracy.

  From the above, it was confirmed that in the drill having a tool diameter of 0.7 mm or less, all of the experimental examples were excellent in breakage resistance and hole position accuracy as compared with the conventional example.

1 Tool body 2a, 2b Chip discharge groove

Claims (9)

  Two cutting edges are provided at the tip of the tool body, and two spiral first chip discharge grooves and second chip discharge grooves from the tool tip to the base end side are provided on the outer periphery of the tool body. The first chip discharge groove includes three twist regions each having a predetermined twist angle, and the second chip discharge groove includes two twist regions each having a predetermined twist angle. Of the chip discharge grooves, one of the chip discharge grooves is connected to a middle portion of the other chip discharge groove, and at least one of the first chip discharge groove or the second chip discharge groove. The chip discharge groove is formed up to a predetermined position on the base end side of the tool body, and from the tool tip side, the two groove portions having the same twist angle of the first chip discharge groove and the second chip discharge groove, The first chip discharge groove and the second chip discharge groove A parallel running part that is arranged continuously with different angles, and a parallel running part that makes the twist angles of the first chip discharge groove and the second chip discharge groove connected in parallel to make both run in parallel. Are provided in order, and the twist angle of the parallel running portion of the first chip discharge groove and the second chip discharge groove is set to be larger than the twist angle of the two groove portions. The change position of the torsional angle located closest to the tool tip side is 1/5 of the groove length of the chip discharge groove formed from the tool tip to a predetermined position 1.5 times the tool diameter or more on the base end side of the tool body. A drilling tool provided at a position of 2 or less.   2. The drilling tool according to claim 1, wherein a twist angle of the parallel running transition portion in the first chip discharge groove is larger than a twist angle of the two groove portions.   The drilling tool according to any one of claims 1 and 2, wherein a difference between a twist angle of the parallel transition portion of the first chip discharge groove and a twist angle of the two groove portions is 3 ° or more and 25 ° or less. Drilling tool characterized by being set to.   The drilling tool according to any one of claims 1 and 2, wherein a difference between a twist angle of the parallel transition portion of the first chip discharge groove and a twist angle of the two groove portions is 5 ° or more and 15 ° or less. Drilling tool characterized by being set to.   5. The drilling tool according to claim 1, wherein a twist angle of the two groove portions of the first chip discharge groove and the second chip discharge groove is set to 30 ° or more and 50 ° or less. Drilling tool characterized by being made.   6. The drilling tool according to claim 1, wherein the twist angle of the parallel running portion of the first chip discharge groove and the second chip discharge groove is greater than the twist angle of the two groove portions. A drilling tool characterized by being set at an angle greater than 2 ° and less than 20 °.   The drilling tool according to any one of claims 1 to 6, wherein the axial groove width of the parallel groove at the start end position of the parallel running part is an axial direction at a change position of a twist angle located closest to the tool tip side. A drilling tool characterized by being set to 1.1 times or more and 1.9 times or less of the groove width.   The drilling tool according to any one of claims 1 to 7, wherein a groove length of one of the two chip discharge grooves is 50% or more of a groove length of the other chip discharge groove. A drilling tool characterized by being set to 95% or less.   9. The drilling tool according to claim 1, wherein the first chip discharge groove and the second chip discharge groove have a narrow angle of rise greater than 90 ° and less than or equal to 180 °. A drilling tool characterized by

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