JP2006088242A - Drilling tool - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a drilling tool, giving a desired surface roughness to the inner surface of a machined hole. <P>SOLUTION: A diamond compact 17 is fitted as ultra-abrasive grain constituting a cutting blade part to the tip of a shank 3 on a shaft. A backing 19 made of cemented carbide is disposed on the rear of the diamond compact. A margin part 17a is provided on the outer peripheral part of the diamond compact, and the surface roughness of the margin part 17a is set to Rz1.0μm or more, which is a roughness corresponding to a required surface roughness for the inner surface of the machined hole. The margin part 19a formed on the outer peripheral part of the backing is also given the same surface roughness. <P>COPYRIGHT: (C)2006,JPO&NCIPI

Description

  The present invention relates to a drilling tool such as a reamer or a drill. More specifically, the present invention relates to a drilling tool in which a superabrasive compact is fixed to the tip of a shaft-shaped shank, and to a drilling tool that can give a desired surface roughness to the inner surface of a processed hole.

  A drilling tool such as a drill or a reamer is known in which a superabrasive compact is fixed to the tip of a shaft-shaped shank having a substantially cylindrical shape or the like, and a cutting edge portion is formed by the superabrasive compact. A drilling tool using a superabrasive compact such as diamond is difficult to make a cutting edge at the time of machining, and can be suitably used particularly for machining aluminum, aluminum-based alloys, and non-ferrous metals.

  Japanese Patent Application Laid-Open No. 2004-17234 discloses a technique in which a rotating cutting tool using a superabrasive compact is subjected to a blunting process on the radially inner portion of a cutting blade to refine the chips. This is because the cutting ability of the cutting edge formed by the superabrasive compact is excellent, so that continuous long chips are generated, and it is difficult to discharge the chips, and the workpiece is processed by the chips. It is intended to prevent the surface from being damaged.

  Japanese Patent Application Laid-Open No. 2003-181711 sets the twist angle of the chip discharge groove to 0 degree at the tip portion having a predetermined length from the tip, and increases the twist angle toward the blade base so as to increase the chip discharge property. An improved ultra-high pressure sintered drill is disclosed.

  Drilling tools using these superabrasive compacts have improved chip evacuation, which has been considered a problem in the past, and the sharpness, long service life, Combined with characteristics such as very good surface roughness, it offers extremely good drilling tools. In particular, regarding the surface roughness, the surface roughness of the contact portion of the cutting edge portion formed by the abrasive compact, that is, the margin portion is usually about Rz 0.4 to 0.6 μm, and when processing using such a tool, An excellent finished surface having an Rz of 0.4 to 0.6 μm can be obtained on the inner surface of the hole.

  By the way, since the aluminum-based material is soft, the machined hole is not used as it is, but it is used by inserting a bush made of a hard material into the hole, such as a valve seat ring of an automobile engine. There are many cases to do. In addition, a metal or resin cap may be fitted into the processed hole to close the hole entrance.

  In recent years, with the advancement of technology, there is often a demand for extremely high dimensional accuracy in various processes. As described above, a drilling tool using a superabrasive compact satisfies this requirement sufficiently. However, in the case of using a bush fitted in a hole processed as described above, the good surface roughness obtained with high dimensional accuracy by a superabrasive compact drilling tool may lead to an undesirable result. is there. That is, when processed with a superabrasive compact drilling tool as described above, a surface close to a mirror surface having a surface roughness smaller than, for example, Rz1.0 is obtained on the inner surface of the hole. For this reason, there arises a problem that the fitted bush and cap are easily removed.

JP 2004-17234 A JP 2003-181711 A

  The present invention has been made in view of the above-mentioned conventional problems, and the inner surface of the processed hole while taking advantage of the excellent sharpness and long life of the superabrasive compact and the high dimensional accuracy of the processed hole as it is. Further, it is an object of the present invention to provide a drilling tool that can provide a desired surface roughness in order to provide a fixing function sufficient to fix the fitted member.

  The present inventors have a certain correlation between the surface roughness given to the margin part of the drilling tool using the superabrasive compact and the surface roughness of the inner surface of the hole processed using this tool, It was found that the surface roughness of the inner surface of the hole can be controlled by controlling the surface roughness of the margin portion, and the present invention was obtained based on this finding. That is, in order to solve the above problems, the present invention provides a drilling tool comprising a shaft-shaped shank and a superabrasive compact fixed to the tip of the shank. Provided is a drilling tool in which the surface roughness of the margin portion formed in is set to Rz 1.0 or more.

  In the present invention, since the above-described configuration is adopted, a desired surface roughness can be imparted to the inner surface of the processed hole while taking advantage of the excellent sharpness and long life of the superabrasive compact. A sufficient fixing force to the bush and cap fitted in the hole is obtained, and it is difficult to come off. Note that the surface roughness of the margin portion of the superabrasive compact can be easily controlled using an appropriate processing method such as laser processing. The surface roughness imparted to the margin portion can withstand long-term use and maintain the roughness, so that holes having the same surface roughness can be stably processed over a long period of time. On the other hand, when machining with a cemented carbide tool, a rough surface is obtained on the inner surface of the hole regardless of the roughness of the margin surface of the cemented carbide tool, which is due to the component cutting edge formed during machining, The roughness is uncontrollable and cannot maintain the same degree of roughness.

  Hereinafter, specific embodiments of the present invention will be described with reference to the drawings. FIG. 1 is a front view of a reamer 1 according to a specific embodiment of the present invention, and FIG. 2 is an enlarged left side view thereof. In the figure, reference numeral 3 denotes a shank made of cemented carbide or steel, and comprises a shank body 5 on the side attached to the machine and a body 7 to which a superabrasive compact described later is attached. The main body 5 has a columnar shape, and the body 7 is formed by forming four grooves 9 as escape grooves for chips extending in the axial direction on a cylinder concentric with the main body 5 at intervals of 90 degrees in the circumferential direction. It is. The groove 9 is formed by a vertical plane 10 passing through the center of the body 7 and a horizontal plane 11 extending in a direction orthogonal to the vertical plane 10 at a position away from the center by a predetermined distance. Since the basic shape of the shank 3 is known and is not the gist of the present invention, a detailed description is omitted.

  Reference numeral 17 denotes a diamond compact as a superabrasive compact, which is attached to a mounting portion 13 formed at the tip end in the axial direction and the radially outer portion of the vertical plane 10 of the groove 9 as is well known. In the present embodiment, as shown in the figure, a cemented carbide backing 19 is stacked on the back side of the diamond compact 17. However, the backing 19 can be configured not to be used. Both of these configurations are known.

  The outer peripheral portion of the diamond compact 17 is a margin portion 17 a, and the shape thereof is an arc centered on the center of the body 7. In the present embodiment, a margin portion 19a is also formed on the outer peripheral portion of the backing 19 disposed on the back side of the diamond compact 17, and the shape thereof is formed by an arc having the same core and the same radius as the margin portion 17a of the diamond compact 17. In addition, the margin portion 17a of the diamond compact 15 and the margin portion 19a of the backing 19 constitute a smoothly continuous margin portion 20 as a whole. In this embodiment, the diamond compact 17 and the backing 19 each have a thickness of 0.5 mm, and the margin 19a of the backing 19 is included in the margin 17a of the diamond compact 17 indicated by the symbol L in the drawing. The thickness of the entire margin portion 20 indicated by symbol M is 1 mm, but is not limited to this.

  Reference numeral 7a denotes a margin portion formed on the body 7, and reference numerals 7b and 7c denote flank surfaces formed at predetermined inclination angles. These configurations are also known. The shape of the margin portion 7a of the body 7 is an arc having the same diameter and concentricity as that of the diamond compact margin portion 15a. The thickness indicated by the symbol N in the figure is 1.5 mm in the present embodiment.

  Here, the surface of the margin portion 17a of the superabrasive compact 17 has a surface roughness of Rz 1.0 μm or more. Thereby, when drilling is performed using this reamer 1, a surface roughness corresponding to the surface roughness of the margin portion 17a of the superabrasive compact 17 is obtained on the inner peripheral surface of the hole. The life of the reamer 1 is long, and during that time, the surface roughness of the margin portion 17a is maintained at the initial roughness, and the surface roughness of the hole to be processed can be stably and repeatedly obtained. Since the surface roughness of the inner peripheral surface of the hole is obtained with a certain correlation with the surface roughness of the margin portion 17a, the surface roughness is obtained in advance corresponding to the surface roughness required for the inner peripheral surface of the hole to be processed. The surface roughness of the margin portion 17a may be determined based on the obtained data.

  The thickness L of the margin portion 17a of the illustrated superabrasive compact 17 is desirably 0.1 to 0.5 mm. If it is 0.1 mm or less, the desired roughness may not be obtained on the inner surface of the hole, and the tool life will be shortened. On the other hand, the thickness of a superabrasive compact that is usually commercially available is 0.5 mm or less, and a superabrasive compact with a thickness exceeding 0.5 mm is expensive. Further, when the backing 19 is disposed on the back side of the superabrasive compact 17 and the margin portion 19a is also formed on the outer peripheral portion of the backing 19 as in the case of the above embodiment, the margin portion of the backing 19 is provided. It is desirable to impart the same surface roughness to the margin portion 17a of the superabrasive compact 17 also to 19a.

  The method for imparting the desired surface roughness to the margin portion 17a of the superabrasive compact 17 is not particularly limited, and for example, shot blasting, etching, electric discharge machining, ion beam machining, laser machining, grinding machining, etc. can be employed. It is. The surface of the margin portion 17a may be uniformly roughened as a whole, or may be formed in a predetermined pattern, for example, a stripe shape or a lattice shape. An example is shown in FIG. Note that FIG. 3B is exaggerated for the sake of representing the characteristics of the surface of the margin portion 31.

As shown in FIG. 3, in this embodiment, a low portion 33 according to a predetermined pattern is formed on the surface of the margin portion 31. In this case, it is the high portion 32 that provides the desired roughness to the inner surface of the hole. In the present embodiment, the surface roughness in the above-described range is given to the high portion 32 by laser processing. Various dimensions such as the pitch of the lower portion 33 and the width of the groove, the size of the height portion 32, and the height difference between the height portion 32 and the lower portion 33 are appropriately set. Is possible. Moreover, the process which gives predetermined | prescribed surface roughness and the process which forms the groove | channel which becomes the low part 33 can be performed by a single operation | work by controlling a laser processing machine suitably.

  In the above embodiment, the example of the reamer has been described as a drilling tool. However, the present invention can be applied to other drilling tools such as a drill, and the type or shape of the drilling tool is particularly important. There is no limit. Further, either a straight blade or a twisted blade with a lead is applicable. Furthermore, the present invention can also be applied to a tool in which a plurality of types of tools such as a drill and a reamer are combined, or a tool having a stepped shape in which cutting blade portions having different diameters are provided in several axial directions. In the case of having outer peripheral surfaces with different diameters such as a stepped shape, the present invention may be applied to all the cutting edge portions or only one cutting blade portion. Detailed description of these will be omitted.

  Five types of diamond compact reamers with an outer diameter of 22 mm and 4 blades were manufactured. The thickness of the outer margin part was all 0.5 mm. A diamond compact with a cemented carbide backing was used. The outer margin part was ground with a diamond wheel, and four kinds of margins were prepared by changing the surface roughness by laser machining, and the remaining one was not laser machined. An aluminum alloy casting (JISH5202: AC4B equivalent) was drilled, and the surface roughness of the inner surface of the hole was measured. The results are shown in Table 1. The machining test conditions were as follows: vertical machining center for the processing machine, φ0.6 mm (preparation hole φ21.4 mm, finishing hole φ22 mm), rotation speed 1585 / min (circumferential speed 110 m / min), and feed 200 mm / min. It was set to min.

  As shown in the above results, a clear correlation is obtained between the surface roughness of the margin portion of the diamond compact and the surface roughness of the inner surface of the processed hole. The surface roughness of the work material to be obtained varies depending on the processing conditions such as the material, machining allowance, tool rotation speed, etc. What is necessary is just to obtain the surface roughness of the margin part corresponding to the required surface roughness and to process the margin part by an appropriate processing method such as laser processing. Of course, it is possible to obtain in advance processing conditions for imparting a desired surface roughness to the margin portion.

It is a front view of the reamer concerning a specific embodiment of the present invention. FIG. 2 is an enlarged left side view of FIG. It is a figure which shows an example of the aspect which gives the surface roughness of a margin part.

Explanation of symbols

1: Drilling tool (reamer) 3: Shank 5: Body 7: Body 9: Groove 13: Mounting part 17: Diamond compact 17a: Margin part of diamond compact 19: Backing 19a: Margin part of backing 20: Margin part

Claims (1)

  In a drilling tool comprising a shaft-shaped shank and a superabrasive compact fixed to the tip of the shank, the surface roughness of the margin portion formed on the outer periphery of the superabrasive compact is Rz1. A drilling tool characterized by being zero or more.

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