JP5781044B2 - drill - Google Patents

Description

  The present invention relates to a technique for improving the machining performance of a drill, and more particularly to a technique for improving the machining accuracy and machining efficiency of a hole when drilling a metal using a drill.

  When drilling a metal with a drill, it is desirable that it can be machined as accurately and as fast as possible. Therefore, the drill is also required to have performance for realizing it. It is known that changing the shape of the cutting edge of a drill has a complicated effect on machining efficiency, tool life, and drilling accuracy. Conventionally, various approaches have been made to deal with such problems. As one of the solutions, improvement of the chisel portion is being studied.

  Patent Document 1 discloses a technology related to a chiselless conical spiral blade drill. When drilling with a drill, the chisel part formed on the drill cutting edge has the effect of suppressing chipping and chipping when the chisel edge is long, but the thrust load increases, and the biting property and centripetality at the beginning of machining deteriorate. There is a problem to do. For this reason, on the tip chisel portion of the conical spiral blade, a pair of cutting edges that form a smooth projecting shape in the cutting rotation direction are positioned at the apex of one conical surface whose inner peripheral end coincides with the axis, When viewed from the bottom, they are smoothly connected to each other on the axis, and the entire length of the pair of cutting edges is formed on the conical surface. By doing this, the chisel is eliminated, and the biting property and centripetality superior to the initial stage of processing can be obtained.

Japanese Patent Laid-Open No. 5-96414

  However, the technique of Patent Document 1 is considered to have the problems described below.

  The drill using the technique of Patent Document 1 has an obtuse angle as the clearance angle of the cutting edge formed by thinning approaches the center of the drill. This is because when thinning is performed on the tip of the drill, the shape becomes shallower as it approaches the center of the drill. As the drill edge becomes obtuse, the thrust load generated during machining tends to increase. As a result, even if the technique of Patent Document 1 is used, it is considered that the processing efficiency and processing accuracy of the drill do not increase as expected.

  Accordingly, an object of the present invention is to provide a drill that can be machined with high efficiency and high accuracy in order to solve such problems.

  In order to achieve the above object, a drill according to an aspect of the present invention has the following characteristics.

(1) and the drill center drill center side cutting position to Shindaka is formed on 0mm to side edge, is disposed on the outer peripheral side of the drill center side cutting edge, it is formed discontinuously with the drill center side cutting edge a drill outer peripheral side cutting edge that, the, to the drill outer periphery cutting edge, the drill center side cutting edge is formed to be inclined by the angle α min, the angle α is, 35 ° below 25 ° or more It is characterized by being set to an angle.

  According to the aspect described in the above (1), it is possible to form different clearance angles for the drill center side cutting edge and the drill outer peripheral side cutting edge. By setting the angle α to 25 ° or more and 35 ° or less, it is possible to form a sharp relief angle also on the cutting center side cutting edge. Therefore, unlike the case where the cutting edge is attached by thinning as in the technique described in Patent Document 1, the clearance angle of the drill center side cutting edge can be provided at an acute angle, so that the thrust load can be reduced. Become. As a result, it is possible to provide a drill capable of high-efficiency and high-precision machining.

(2) In the drill according to (1), the relief angle of the drill center side cutting edge is formed to be an acute angle with respect to the drill outer peripheral side cutting edge.

  According to the aspect described in (2) above, since the clearance angle of the drill center side cutting edge is more acute than the drill outer peripheral side cutting edge, the generation of thrust load is further suppressed by making the drill center side cutting edge an acute angle. The initial bite can be improved. Further, when the machining progresses, the drill outer peripheral side cutting edge disposed outside the drill center side cutting edge acts on the machining. Since the cutting edge on the outer peripheral side of the drill is set to the optimum clearance angle, the machining accuracy can be improved.

(3) In the drill according to (1) or (2), it is preferable that a core height of the drill outer peripheral side cutting edge is formed to be 0 mm. By the aspect as described in (3), it contributes to reduction of a thrust load.

It is a bottom view top view of the burnishing drill of a 1st embodiment. It is a side view of the burnishing drill of a 1st embodiment. It is a figure which shows the front-end | tip shape of the burnishing drill of 1st Embodiment. A semi-logarithmic graph of the processing performance of the burnishing drill of the first embodiment It is a graph regarding the thrust load of the first embodiment. It is a graph regarding position accuracy of a 1st embodiment. It is the bottom view of the burnishing drill prepared for the comparison. It is a side view of the twist drill of 2nd Embodiment.

  First, a first embodiment of the present invention will be described with reference to the drawings.

In FIG. 1, the top view which looked at the burnishing drill 10 of 1st Embodiment from the bottom is shown. FIG. 2 shows a side view of the burnishing drill 10. FIG. 3 is a plan view and a side view showing the tip shape of the burnishing drill 10. (A) is a bottom plan view, (b) is an angle of 45 degrees, (c) is a side view, and (d) is a side view from an angle of 75 degrees. The burnishing drill 10 includes a drill center-side cutting edge 11 and a drill outer peripheral-side cutting edge 12 on the outer periphery thereof, and four guide pads 13. The drill center side cutting edge 11 is formed by advancing the angle α in the rotational direction of the burnishing drill 10 with respect to the drill outer peripheral side cutting edge 12. Center height h ₂ of the center height h ₁ and the drill outer peripheral side cutting edge of the drill center side cutting edge of the burnishing drill 10 is set so as to 0mm, the length of the chisel edge C is also set to be 0mm . As shown in FIG. 2, the burnishing drill 10 is a straight blade drill called a burnishing drill.

  The length of the drill center side cutting edge 11 is set to a half length with respect to the length of the drill outer peripheral side cutting edge 12. The length ratio between the drill center side cutting edge 11 and the drill outer peripheral side cutting edge 12 is about 1: 2, or the diameter of the drill center side cutting edge 11 is 0.3 to the diameter of the burnishing drill 10. It is desirable to set it to about 0.4 times. Different clearance angles are formed on the drill center side cutting edge 11 and the drill outer periphery side cutting edge 12, respectively, and the clearance angle of the drill center side cutting edge 11 is set to an acute angle with respect to the drill outer periphery side cutting edge 12. The burnishing drill 10 is made of a cemented carbide containing tungsten carbide and cobalt, which improves high-speed cutting performance, but does not prevent other materials from being used.

  The tip angle θ of the burnishing drill 10 is set to 135 degrees as shown in FIG. 2, and the drill center side cutting edge 11 and the drill outer peripheral side cutting edge 12 are arranged at the drill center arranged on the inner peripheral side of the burnishing drill 10. The side cutting edge 11 and the drill outer peripheral side cutting edge 12 arranged on the outer peripheral side of the burnishing drill 10 form a discontinuous blade. Since the drill center-side cutting edge 11 is formed so as to continue with the center point O in between, the length of the chisel edge C is 0 mm as described above. The cutting edge of the burnishing drill 10 is formed point-symmetrically about the center point O.

  Since the burnishing drill 10 according to the first embodiment has the above-described configuration, the following effects can be obtained.

  First, the burnishing drill 10 can be used with high efficiency and high accuracy. This is because the burnishing drill 10 of the first embodiment has a center height of 0 mm, a drill center-side cutting edge 11 located on the drill center side, and a drill outer periphery disposed on the outer periphery side of the drill center-side cutting edge 11. The drill center side cutting edge 11 is inclined with respect to the drill outer peripheral side cutting edge 12 by an angle α, and the angle α is set to an angle of 25 ° to 35 °. It is what. For this reason, it is possible to provide a drill capable of high-efficiency and high-precision machining with a straight blade.

  FIG. 5 shows a graph relating to cutting resistance. FIG. 6 shows a graph relating to position accuracy. In FIG. 5, the burnishing drill 100 is shown as “conventional drill”, and the burnishing drill 10 is shown as “invention drill”. In FIG. 7, the bottom view of the burnishing drill 100 shown as a conventional drill is shown. A burnishing drill 100 shown as a conventional drill has a cutting edge 111 and a guide pad 113. The center height h is set to about 0.2 mm, and the length of the chisel edge C is set to about 0.5 mm. FIG. 5 and FIG. 6 show a comparison between the burnishing drill 100 and the burnishing drill 10. In FIG. 5, the thrust loads of the burnishing drill 100 and the burnishing drill 10 are compared. It can be seen that the thrust load of the burnishing drill 10 is reduced by 25% with respect to the burnishing drill 100 at a feed amount f = 0.5 mm / rev. This is considered to be due to the fact that the chisel edge C is made as short as possible.

  As shown in the burnishing drill 100, the drill that processes metal has a portion that does not contribute to processing, which does not have a rake face called the chisel portion described above. As a result of the chisel portion being near the center of the drill blade, a large thrust load is generated. In the burnishing drill 10, since the length of the chisel edge C is set to 0 mm, it is considered that this thrust load can be reduced, resulting in a reduction in cutting resistance.

  Moreover, since the drill center side cutting edge 11 and the drill outer peripheral side cutting edge 12 can form different clearance angles, it is possible to make each clearance angle an acute angle. When the cutting edge is formed by thinning as shown in Patent Document 1, it is inevitable that the clearance angle becomes obtuse as the clearance angle approaches the center. However, in the case of the burnishing drill 10, the drill center-side cutting edge 11 is the burnishing drill 10. Since it is formed at an acute angle even in the vicinity of the center, it is possible to contribute to the reduction of the thrust load, and the biting at the initial stage of processing can be improved. As a result, a reduction in cutting resistance can be realized.

  In addition, since the drill outer peripheral side cutting edge 12 is disposed on the outer peripheral side of the burnishing drill 10 as compared with the drill center side cutting edge 11, the drill center side cutting edge 11 first started to act on the processing first. After that, the drill outer peripheral cutting edge 12 begins to act on the machining. For this reason, even if the relief angle of the drill outer peripheral cutting edge 12 is an obtuse angle than the drill center side cutting edge 11, the cutting resistance can be reduced as compared with the burnishing drill 100 because it is an angle larger than the relief angle of the burnishing drill 100. .

  Further, by using the burnishing drill 10, the processing position accuracy is higher than that of the burnishing drill 100 as shown in FIG. 6. This is due to the improved centripetal nature of the drill blade. When the chisel edge C has a certain length as in the burnishing drill 100, the chisel portion is pushed into the workpiece, so that the centripetality is also lowered. However, if the chisel edge C can be set to 0 mm as in the burnishing drill 10, the centripetality is improved.

  In FIG. 4, the semi-logarithmic graph shows the processing performance of the burnishing drill 10. The vertical axis shows IT grade representing accuracy, and the horizontal axis is a log-log graph showing machining efficiency in semilogarithm. The IT grade indicates that machining with higher accuracy is possible as the number of the grade becomes smaller, and the machining efficiency V · f indicates that machining can be performed at higher speed as the number becomes larger. In FIG. 5, the burnishing drill 100 is shown as “conventional drill”, and the burnishing drill 10 is shown as “invention drill”. According to the burnishing drill 10, the V · f value indicating the machining efficiency has achieved 100, and the IT grade has achieved 7. That is, the workpiece can be processed with high accuracy and high efficiency. This means that the machining time is 1/3 to 1/5 and the machining accuracy is higher than that of the conventional burnishing drill 100. Actually, the roundness and the surface roughness were measured, but the value of the burnishing drill 10 was better than that of the burnishing drill 100. It has also been confirmed that the generation of burrs is small with respect to burrs in the penetrating portion.

  The reason why such a result is obtained is that the burnishing drill 10 has a composite blade formed by dividing the cutting center side cutting edge 11 and the drill outer peripheral side cutting edge 12, so that the chips are divided and the cutting is performed. It is considered that the waste is discharged smoothly. Chips tend to become longer as the length of the cutting edge becomes longer, and non-ferrous metals such as aluminum are particularly likely to deteriorate chip discharge. For this reason, it is considered that by cutting the workpiece with the divided composite blades of the drill center side cutting edge 11 and the drill outer peripheral side cutting edge 12, the chips can be easily divided and the chip discharge performance is improved. . Moreover, since the clearance angle of the drill outer peripheral cutting edge 12 contributes greatly to the machining accuracy, the clearance angle of the drill outer peripheral cutting edge 12 is optimized to improve the machining accuracy, thereby contributing to the improvement of the machining accuracy. it can. By brazing diamond convax or the like to the drill outer peripheral cutting edge 12, the affinity with the work material is lowered, and the machining accuracy can be further improved.

  Next, a second embodiment of the present invention will be described. Unlike the burnishing drill 10 of the first embodiment, the twist drill 50 of the second embodiment has a structure in which two spiral grooves are cut in the main body.

  FIG. 8 shows a side view of the twist drill 50. As with the burnishing drill 10 shown in the first embodiment, the twist drill 50 is formed at a position where the drill center-side cutting edge 11 is advanced in the machining direction by an angle α with respect to the drill outer peripheral-side cutting edge 12. Yes. A clearance angle is set for each of the drill center side cutting edge 11 and the drill outer periphery side cutting edge 12, and the clearance angle of each drill center side cutting edge 11 is sharper than that of the drill outer periphery side cutting edge 12. It is formed as follows. On the other hand, the side view of the twist drill 50 shows a state in which the drill center-side cutting edge 11 and the drill outer peripheral-side cutting edge 12 formed in the twist drill 50 are formed in a spiral shape. The bottom view is the same as that in FIG. 1, and the guide pads 13 are also provided at four locations.

  And by taking such a structure, it becomes possible to acquire the effect equivalent to 1st Embodiment. That is, by providing the twist drill 50 with the drill center side cutting edge 11 having an acute clearance angle and the drill outer peripheral side cutting edge 12 having an obtuse angle, it is possible to improve the biting at the initial stage of machining, and to reduce the thrust load. Reduction can be realized and machining efficiency can be improved. Moreover, since the drill center side cutting edge 11 and the drill outer peripheral side cutting edge 12 are discontinuous, it becomes easy to sever a chip | tip and the discharge property of a chip improves. Further, since the clearance angle of the drill outer peripheral cutting edge 12 can be optimized, it is possible to improve the processing accuracy.

  Although the invention has been described according to the present embodiment, the invention is not limited to the first embodiment and the second embodiment, and the configuration of the invention is within a range not departing from the gist of the invention. It can also be implemented by appropriately changing the part. For example, although the material of the burnishing drill 10 is shown in 1st Embodiment, it is not limited to this, The coating generally performed with respect to the burnishing drill 10 is not prevented. For example, even if a coating such as TiN, TiCN, TiAlN or the like is applied according to the processing purpose, the object of the invention is not hindered.

10 Burnishing drill (Invention drill)
11 Drill center side cutting edge 12 Drill outer peripheral side cutting edge 13 Guide pad 50 Twist drill 100 Burnishing drill (conventional drill)
111 Cutting edge 113 Guide pad α Angle C Chisel edge O Center point h Core height h ₁ Drill center side cutting edge core height h ₂ Drill outer peripheral side cutting edge core height

Claims (3)

And drill center side cutting edge Shindaka located drill center side formed to 0 mm,
Wherein disposed on the outer peripheral side of the drill center side cutting edge has a, with the drill center side cutting edge and discontinuously formed Ru drill outer peripheral side cutting edge,
The drill center side cutting edge is formed to be inclined by an angle α with respect to the drill outer peripheral side cutting edge,
The angle α is set to an angle of 25 ° to 35 °,
A drill characterized by. The drill according to claim 1,
The clearance angle of the drill center side cutting edge is formed at an acute angle from the drill outer peripheral side cutting edge,
A drill characterized by. The drill according to claim 1 or 2,
The core height of the drill outer peripheral side cutting edge is formed at 0 mm,
A drill characterized by.

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