JP2008000836A - Drill - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To form a high-quality through-hole without any burrs in a work material of CFRP or the like in which the burrs are easily formed by machining by a drill, and to drastically improve the service life of the drill. <P>SOLUTION: A drill body 3 is provided with a preceding work part 4 for drilling a preparatory hole in the work material and a finishing part 5 having a finishing blade 7 on the tip. A diameter difference between the outside diameter ϕD2 of the finishing part 5 and the outside diameter ϕD1 of the preceding work part 4 is adjusted to be above 0.1 mm and below 2.0 mm. A chip discharging groove 8 is formed as a high-helix groove having a torsion angle β of 40° or larger, and the surface of the drill body 3 is covered with a diamond coating. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention is particularly suitable for drilling a fiber reinforced composite material represented by CFRP (carbon fiber reinforced plastic), and more specifically, a high-grade penetration without so-called burrs at the hole outlet in one drilling operation. The present invention relates to a drill capable of making more holes in a fiber reinforced composite material or the like.

  A through-hole processed by a drill tends to generate burrs at the edge of the outlet. In order to suppress the occurrence of such burrs, the following Patent Document 1 configures a drill for FPC (flexible substrate) processing as follows. That is, at least the blade portion is formed of any one of cemented carbide, cermet, ceramics, ultra-high pressure sintered body, or a material coated with a hard coating. In addition, the flank is formed by the second flank and the third flank, and the flank angle of the third flank is set to 33-50 °, thereby shortening the length of the cutting edge on the outer peripheral side of the chisel blade. Thus, the width of the chips generated by the cutting edge is reduced, thereby improving the chip dischargeability and suppressing burrs generated due to poor dischargeability.

  Patent Documents 2 and 3 below disclose drills that provide a small-diameter portion on the tip side to suppress burrs at the through-hole exit.

The following Patent Document 4 discloses a double angle drill in which a primary cutting edge having a tip angle of 118 ° and a secondary cutting blade having a tip angle of about 30 ° are connected as a drill suitable for simultaneous drilling of CFRP and an aluminum alloy plate. ing.
JP 2005-88088 A JP 2001-54810 A Japanese Utility Model Publication No. 1-99517 Utility Model Registration No. 2602032

  Fiber reinforced composite materials, especially CFRP, are lightweight and have high strength and rigidity, and are frequently used as structural materials for aircraft. The CFRP material for aircraft has strict requirements regarding quality, and is required to have no burrs protruding on the mating surface with other members.

  However, the CFRP contains hard-to-cut carbon fibers. Therefore, in the processing of the through hole, burrs are more likely to occur at the hole exit than the work material formed of a single material of resin or metal, and the above-mentioned patent The measures disclosed in Documents 1 and 2 cannot provide a practically sufficient effect.

  Patent Document 3 does not particularly mention the material of the work material. However, as in Patent Document 2, since only a small-diameter portion is formed on the tip side of the drill, when the work material is CFRP, the technique of Patent Document 3 can also provide a satisfactory effect for suppressing burrs. I can't.

  For this reason, when high quality is desired in the drilling of CFRP, a dedicated drill as disclosed in Patent Document 4 is adopted, but the double-angle drill of Patent Document 4 has a problem in durability. The actual situation is that burrs are generated at the exit of the hole due to the machining of ˜40 holes, and the tool must be changed.

  The present invention has been made in view of the above, and makes it possible to drill a high-quality through hole without a burr in a work material by machining with a drill, and drastically improve the life of the drill. It is an issue.

In order to solve the above-described problems, in the present invention, a drill for forming a through hole having a diameter of φD2 is configured as follows. In other words, the drill body is finished with a pre-machined part that drills a pilot hole in the work material and a finishing blade at the connecting part between the pre-machined part that is larger in diameter than the pre-machined part connected to the back of the machined part. With
(1) The diameter difference between the outer diameter φD2 of the finished portion and the outer diameter φD1 of the preceding processed portion is 0.1 mm or more and 2.0 mm or less.
(2) The chip discharge groove provided on the outer periphery of the drill body is formed as a strongly twisted groove having a twist angle β of 40 ° or more.
(3) The surface of the drill body is covered with a diamond coating.
The above requirements must be met together.
Note that the diameter φD2 of the through hole referred to here is a diameter in which processing errors are ignored.

In this drill, it is preferable that the length L of the portion having the outer diameter of φD1 of the preceding processed portion is set to 0.2 mm or more. Depending on the material of the work material, it may be preferable to configure the outer peripheral cutting edge of the finished portion as a cutting edge having a positive rake angle of 10 to 30 °.

  The pre-machined part of this drill may be provided with a small diameter part having an outer diameter smaller than φD1 in front of the part having the outer diameter of φD1 so that the pilot hole is processed stepwise. The part having the outer diameter of φD1 of the preceding processed part with respect to the finished part has a diameter difference of 0.1 to 2.0 mm.

  The drill of this invention has a variability due to the synergistic effects of causing a difference in diameter between the preceding machined part and the finished part, making the chip discharge groove into a highly twisted groove, and covering the surface of the drill body with a diamond coating. High-quality holes can be machined, and the service life can be dramatically improved.

  When a through hole is drilled with a general drill that does not have a pre-machined part, the cutting resistance when the outer peripheral part of the drill's frontmost part passes through the work material is large, so that the work material is pushed out of the hole. However, if a pre-processed part is provided and a pilot hole is drilled first, the machining allowance by the finished part is reduced, and therefore the resistance when the finished part passes through the work piece is reduced. . In addition, the cutting load of the finishing blade is reduced, the good sharpness of the finishing blade is maintained for a long time, and the removability of the burr generated in the pilot hole is improved by the finishing blade. Is done.

  The above-mentioned Patent Documents 2 and 3 disclose that a diameter difference is generated in a drill. However, particularly when the work material is a fiber reinforced composite material such as CFRP, the diameter difference is merely generated. We cannot expect satisfactory effect.

  Therefore, in the present invention, the chip discharge groove is a strongly twisted groove, and in addition to this, the surface of the drill body is further covered with a diamond coating. If the chip discharge groove is a strongly twisted groove, the finishing blade becomes sharp and sharpness is improved, and burrs are less likely to occur. In addition, by covering the surface of the drill body with a diamond coating, the life is drastically improved and a good sharpness of the cutting edge is maintained for a long time. The diamond coating has a small coefficient of friction, and a reduction in cutting resistance thereby has an effect of suppressing burrs. When specializing in processing of fiber reinforced resin such as CFRP, the finished blade can be a cutting blade having a positive rake angle of 10 to 30 °, for example. By providing this cutting edge, the burr suppression effect can be maintained for a longer time.

  The above-mentioned Patent Document 1 discloses that the twist angle of the chip discharge groove is larger than that of a general drill, and Patent Document 4 discloses that the surface of the drill body is covered with a diamond coating. High-quality through-holes cannot be made in fiber-reinforced composite materials only by countermeasures. The object of the invention can be achieved by combining all the above-described configurations.

  In addition, said effect is acquired when the diameter difference of a preceding process part and a finishing part is set to 0.1-2.0 mm. This difference in diameter is too small at 0.1 mm or less, and burrs generated by processing by the preceding processed portion cannot be reliably removed with the finishing blade. On the other hand, if the diameter difference is 2.0 mm or more, the load of the finishing blade becomes too large and new burrs are generated in the hole processed by the finished portion.

  Embodiments of the present invention will be described below with reference to FIGS. 1 to 6 of the accompanying drawings. The drill 1 in FIG. 1 is a so-called two-blade drill, and a drill body 3 is integrally connected to the tip of a shank 2.

The drill main body 3 is formed of a cemented carbide or the like, and has a preceding machining portion 4 and a finishing portion 5 having a larger diameter than the preceding machining portion 4 integrally connected to the rear of the preceding machining portion. As shown in FIG. 2, the preceding machining unit 4 has two cutting edges (preceding blades) 6 and 6 extending from the center of rotation to the outer periphery of the preceding machining unit 4 at the tip, and the finishing unit 5 is a preceding machining unit. 4 has a finishing blade 7 (see FIG. 1) for machining a portion left uncut by 4. In addition, two twisted chip discharge grooves 8 corresponding to each cutting edge are provided on the outer periphery of the preceding processing portion 4 and the finishing portion 5.

  Α1 in FIG. 1 is a tip angle, which is set to an angle of about 118 to 160 °. α2 is a tip angle of the finishing blade 7 (step angle referred to as a step drill), and is set in a range of 90 to 160 °.

  In FIG. 1, φD1 is the outer diameter of the preceding processed portion 4, φD2 is the outer diameter of the finished portion 5, and the difference in diameter (φD2-φD1) is set to be in the range of 0.1 to 2.0 mm. Has been. The reason was already mentioned.

  The chip discharge groove 8 provided on the outer periphery of the drill body 3 is formed as a strongly twisted groove having a twist angle β of 40 ° or more. The reason why the chip discharge groove 8 is strongly twisted has already been described. The torsion angle β of the chip discharge groove 8 depends on the size of the tip angle and the material of the work material, but the upper limit is limited to about 60 ° in order to prevent the cutting edge from becoming too sharp and easy to chip. Is good.

  The surface of the drill body 3 is covered with a diamond coating 9 as shown in FIG. The coating 9 is formed by, for example, a well-known CVD method as disclosed in Patent Document 4.

  In addition, L of FIG. 1 is the length of the part which has the outer diameter of (phi) D1 of the preceding process part 4, and this has ensured the length of 0.2 mm or more. The length L of this portion can be freely increased as long as there is no problem in maintaining the strength of the drill body. However, it is not preferable to lengthen L unnecessarily because it increases the drill stroke during drilling. The effect of the drill of the present invention is exhibited when the length L of the portion having the outer diameter of φD1 of the preceding machining portion 4 is made larger than the feed amount of the drill (feed amount per rotation). Since the condition of the feed amount of 0.1 mm or less is adopted, the effect of the invention can be surely exhibited if the length L is set to 0.2 mm or more.

  In FIG. 1, 10 is a margin. In the illustrated drill, the margin 10 is provided on the outer periphery of the finishing portion 5. If the above-mentioned length L is short, it is difficult to provide a margin 10 on the outer periphery of the preceding processed portion 4, so the drill of the embodiment has a structure in which the preceding processed portion 4 has no margin.

  In the illustrated drill, the chip discharge groove 8 is a strongly twisted groove having a twist angle β of 40 ° or more, so that the angle of the cutting edge of the finishing blade 7 is sharpened and the sharpness is improved as shown in FIG. As shown in FIG. 5, a drill specialized in processing of fiber reinforced resin or the like typified by CFRP has an outer peripheral cutting edge 11 of the finishing portion 5 (blade formed at the intersection ridge of the margin 10 chip discharge groove 8). The sharpness can be remarkably improved by setting the rake angle γ to a positive rake angle of, for example, 10 to 30 °. When the angle of the cutting edge becomes too sharp, lands that blunt the cutting edge are formed on the cutting edge to reinforce the cutting edge, but drills specialized for processing fiber reinforced resin etc. have a long life even if the cutting edge is sharp Therefore, it is possible to maintain a good sharpness of the outer peripheral cutting edge for a long time, whereby the burrs generated by the processing by the preceding processing portion 4 are effectively cut out by the finishing blade 7 and processed into holes. The quality of is improved.

  In addition, as shown in FIG. 6, the prior | preceding process part 4 may be formed in the multistage of 2 steps | paragraphs or more. The drill of FIG. 5 is provided with a small-diameter portion 4a having an outer diameter φD smaller than φD1 in front of a portion having an outer diameter of φD1, so that the drilling of the prepared hole by the preceding processed portion 4 is performed in stages. Even with such a structure, the effects of the invention can be obtained. When such a structure is employed, the difference between the outer diameter φD1 of the part where the pilot hole is finally processed and the outer diameter φD2 of the finished part 5 is set to 0.1 to 2.0 mm.

The results of tests conducted for performance evaluation of the drill of this invention are shown below.
-Evaluation test 1-
In the test, first, the effect of burr suppression by using a step drill as shown in Patent Documents 2 and 3 was examined.
Using a drill with the following specifications, a through hole was machined in the work material under the following cutting conditions. 7 types of drills, in which the difference in diameter between the outer diameter φD1 of the pre-processed portion 4 and the outer diameter φD2 of the finished portion 5 shown in FIG. The durability until burrs began to occur was examined.
Drill used: Finished part outer diameter φ6mm, 2-flute, helix angle 30 °, made of cemented carbide, dimensions shown in Fig. 7
Method L = 1.5mm
Cutting conditions: Cutting speed V = 100 m / min, feed f = 0.06 mm / rev
Work material: CFRP (8mm thickness)
The test results are shown in Table 1.

  From this test result, when using a step drill, if the diameter difference between the finished part and the preceding process part is set appropriately, a slight burr suppression can be achieved with CFRP processing compared to when using a drill without a step. Although it can be seen that an effect can be obtained, the obtained effect is not satisfactory in practice.

-Evaluation test 2-
Next, the effect of burr suppression by the twist angle and the diamond coating was evaluated by the following test.
In the test, a through hole was machined in the work material under the following cutting conditions using a drill having the following specifications. Seven types of drills with different helix angles and the presence or absence of diamond coating were made as prototypes, and the durability of each drill was examined.
Drill used: outer diameter φ 6 mm, 2-flute, made of cemented carbide Cutting conditions: Cutting speed V = 100 m / min, Feed f = 0.06 mm / rev
Work material: CFRP (8mm thickness)
The test results are shown in Table 2.

  From this test result, it can be seen that it is effective to suppress the burrs by making the chip discharge groove a strong twist of 40-60 ° and providing a diamond coating on the surface of the drill body. However, the number of processed holes is limited to about 100, and it can be seen that the sustainability of the effect cannot be dramatically increased.

-Evaluation test 3-
In addition to this, the effect of burr suppression of a drill having a stepped structure as a drill body was evaluated by the following test.
Drill used: Finished part outer diameter φ6mm, 2-flute, made of cemented carbide, dimension L in Fig. 7 = 1.5mm
Cutting conditions: Cutting speed V = 100 m / min, feed f = 0.06 mm / rev
Work material: CFRP (8mm thickness)
The test results are shown in Table 3.

  As can be seen from this test result, the load on the finishing blade at the tip of the finished part is reduced by providing a pre-machined part and a finished part with a diameter difference in a high-torsion drill with a diamond coating. Is significantly improved, and the good sharpness of the blade is maintained for a long time, so that the life of the drill (the life until burrs are generated) is dramatically extended. The drill used in Evaluation Test 2 has a service life of 100 processed holes, whereas the inventive drills (Sample Nos. 2 to 4 and 7 to 9 in Table 3) have 500 processed holes. However, good results have been obtained, and the lifetime has increased by more than five times compared with the drill used in the evaluation test 2.

  In evaluation test 3, sample Nos. 5 and 10 in which the diameter difference between the finished part and the preceding processed part was 2.5 mm were also extended to almost double the life of sample No. 1 with no diameter difference. However, the life extension rate of the inventive drills of Sample Nos. 2 to 4 and 7 to 9 is extremely large. From this difference in effect, the effectiveness of setting the diameter difference between the finished part and the preceding processed part to 0.1 to 2.0 mm can also be read.

Side view showing an example of the drill of the present invention 1 is an enlarged front view of the drill of FIG. 1 is an enlarged cross-sectional view of the tip of the drill of FIG. Enlarged sectional view of the finishing blade Enlarged sectional view of the peripheral cutting edge The figure which shows the outline | summary of the other example of the drill of this invention Diagram showing dimensions of drill used for evaluation test

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Drill 2 Shank 3 Drill main body 4 Prior process part 4a Small diameter part 5 Finishing part 6 Cutting edge (preceding edge)
7 Finishing edge 8 Chip discharge groove 9 Diamond coating 10 Margin 11 Perimeter cutting edge

Claims (4)

A drill that drills a through hole having a diameter of φD2, in which a drill body (3) has a preceding machined part (4) for drilling a pilot hole in a work material, and a preceding machine that is provided behind the preceding machined part (4). A finishing portion (5) having a larger diameter than the processing portion and having a finishing blade (7) at the tip;
1) The diameter difference between the outer diameter φD2 of the finished portion (5) and the outer diameter φD1 of the preceding processed portion (4) is 0.1 mm or more and 2.0 mm or less.
2) The chip discharge groove (8) provided on the outer periphery of the drill body (3) is formed as a strongly twisted groove having a twist angle β of 40 ° or more.
3) The surface of the drill body (3) is covered with a diamond coating (9).
A drill characterized by satisfying all requirements.   The drill according to claim 1, wherein a length L of a part having an outer diameter of φD1 of the preceding machined part (4) is set to 0.2 mm or more.   The preceding processed portion (4) has a small diameter portion (4a) in front of a portion having an outer diameter of φD1, and the outer diameter of the small diameter portion (4a) is smaller than φD1, and is determined by the preceding processed portion (4). The drill according to claim 1 or 2, wherein the pilot hole is processed step by step.   The drill according to any one of claims 1 to 3, wherein the outer peripheral cutting edge (11) of the finishing portion (5) is configured as a cutting edge having a positive rake angle of 10 to 30 °.

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