JPS62207590A - Manufacture of small diameter drill - Google Patents

Abstract

PURPOSE:To reduce a manufacturing cost by performing the electron beam welding of the PCD chip in the prescribed length consisting of a diamond sintered body and sintered hard alloy to the super alloy member of a drill body with Ni as a filler material. CONSTITUTION:The PCD chip 20 in <=3mm length which is arranged at the drill tip part and which is composed of a diamond sintered body and sintered hard alloy member is prepared in advance. The PCD chip 20 is first placed by pinching the Ni plate 61 of a filler material by holding the sintered hard member 40 of the drill with a shank part 42 to a chuck 60. The PCD chip 20 and sintered hard member 40 are located concentrically by a copper made jig 62 to apply a light pressure P. This composition is worked in a small diameter drill after welding by irradiating an electron beam 63 on a junction part 61 by arranging it in the vacuum of the electron beam welding equipment. In this way the manufacture of the small diameter PCD drill is simplified and the manufacturing cost can be reduced.

Description

[Detailed description of the invention] [Minute hand for industrial use] The present invention relates to a method for manufacturing a diamond sintered drill, Masuko's CBN sintered drill, for drilling small diameter holes of 2 m+i or less, particularly 1 m or less. be.

[Conventional technology]

For drilling small diameter holes, a straight shank drill made of high speed steel is generally used for light machining, and a luma type drill made of cemented carbide is used for light machining.

Here, small diameter is defined as 2 m or less, but there are many problems especially with extremely thin objects under ll11. As shown in FIG. 2, the Columa type is a tool type consisting of a drill body 1 of a predetermined diameter having a cutting edge portion 2 and a spiral groove 3, and a shank 4 having a larger diameter than the drill body 1.

An example of light machining is drilling holes in printed wiring boards for electronic devices. The substrate is a difficult-to-cut material that causes considerable wear and tear on tools, and it is necessary to drill a large number of small-diameter holes in it in a short period of time. Demand for this type of machining has increased in recent years, but even cemented carbide drills have a short lifespan due to light machining, so automation and
This is an obstacle to mass production.

Diamond sintered body (PCI) is a tool material that has better wear resistance than cemented carbide.

Since the life of cutting tools is several tens to a hundred times longer than that of cemented carbide, it is expected to be applied to small-diameter drills.

Figure 3 10 shows a PCD supplied for general cutting tools.
It is blank. It has a structure in which a layer 11 of diamond sintered body is provided with a lining 12 of cemented carbide, the thickness of the diamond layer 11 is 0.5 mm, the total thickness including the lining 12 is 15 to 3,
Or, the diameter is generally 8 to 13 (all units are mm).

Various types of cutting tools are constructed by machining a blank 10 to form a PCD "chip" to form a cutting part and silver-brazing it to a shank made of steel or the like. The cemented carbide part 12 shown in FIG. 3 not only reinforces the diamond sintered body 11 but also makes it possible to braze the tip to the shank. However, since the diamond sintered body deteriorates when heated above 700°C, care must be taken when applying silver brazing. Due to this reason, the brazing strength may be insufficient and the chip may fall off.

For small diameter drills, there is a PCD blank 30 shown in FIG. A drill body is manufactured in which a round bar-shaped blank 3° consisting of a diamond sintered body part 31 and a cemented carbide part 32 has various diameters up to a minimum of about 1 mm, and lengths have the diamond sintered body 31 as the cutting edge part. is sufficient.

Although the manufacturing technology for general PCD tools has been almost completed and the PCD blank 3o shown in FIG. 5 is also available, the small diameter drill ζ has not been put into practical use due to the above-mentioned difficulties.

[Problem that the invention seeks to solve]

To manufacture a small diameter drill from the PCD blank 10 of FIG. 3, cut out a small cylinder as shown in FIG. 4 20 perpendicularly to the plate surface of the blank 10, and use the PCD "chip" 20 shown in FIG. 2 as the tip of the drill. The thickness of the diamond sintered body portion 21 is sufficient to form the tip of a small diameter drill. As shown in FIG. 6, the cemented carbide portion 22 of the chip 20 is joined to the cemented carbide member 40 to form a lumer-shaped worker shape. The member 40 has an integral structure including a body portion 41 having a predetermined diameter and a shank portion 42 having a standard diameter. After joining, the drill tip and the spiral groove of the body are machined to complete the small diameter drill as shown in Fig. 2.

Conventionally, the bond 43 between the PCD chip 20 and the body part 41 is made by silver brazing, as described above, but the chip 20 tends to reach a high temperature as a whole due to heating of the extremely small T-coat joint 43, so diamond sintering is required. There is a great risk of deteriorating the body 21. Furthermore, since the bonding area is small, sufficient bonding strength cannot be obtained. The drill is subjected to strong torsional stress during drilling, but the shear strength of the silver brazed part is insufficient, making it unusable as a mold drilling drill.

The PCD blank 30 shown in FIG. 5 does not have the above-mentioned difficulties because it can be processed to integrally manufacture a drill body including the drill tip, but there is a problem in joining it to the shank. As shown in FIG. 7, the PCD blank 30 can be inserted and fixed into the hole 51 at the tip of the shank 50 by silver brazing or press fitting.

In the case of wI brazing, the diamond sintered body 31 is heated in the heating section 3.
3, there is little risk of overheating, and since the brazed area is large, the joint strength is sufficient. But the 8th rI! There must be at least a gap between the hole 51 of the J shank 50 and the blank 33 for the solder material 52 to enter, resulting in a fit with so-called play, and the blank 30 is It is fixed with a fall.

In the press-fitting method, the hole 51 of the steel shank 50 is blank 30.
The blank 30 is pushed into this diameter.

The shank 50 receives the blank 30 with the hole 51 forcibly enlarged, but the local deformation of the shank for this purpose is not necessarily uniform, resulting in collapse as shown in FIG. Further, the diamond sintered body 31 may be damaged due to the strong pressure of pushing.

Collapse is unavoidable with both silver brazing and press fitting methods. The process of joining the blank 30, which is slightly thicker than the predetermined drill diameter, to the shank and then grinding the blank 30 so that it has the predetermined diameter and is coaxial with the shank becomes extremely difficult due to the inclination shown in FIG. Not only does the amount of grinding increase in proportion to the inclination, but also the tip shakes when the shank is chucked and rotated, so the machining must be done extremely gradually to avoid the risk of the blank 30 breaking due to the grinding pressure. .

As an example, when the tip of a blank with a diameter of 0.8 mm and a length of 12 mm had an eccentricity of 36 μm, it took about 4 hours to perform the grinding process to correct this. The four-hour process, which requires careful attention, significantly reduces the manufacturing efficiency of small-diameter drills and increases manufacturing costs, which is completely unacceptable.

[Means for solving problems]

An object of the present invention is to economically provide a small diameter PCD drill with high precision and high performance.

In the small diameter PCD drill of the present invention, the PCD drill shown in FIG.
The structure shown in FIGS. 7 and 8 using the blank 30 involves the problem of falling, so this is avoided, and the structure shown in FIG. 6 using the small chip 20 of PCD is adopted. Joining of chip 20 and member 40 4
3, silver brazing is not possible as mentioned above. In place of this, the present invention has established a joining method that does not cause the diamond sintered body 21 to deteriorate due to overheating, but can still provide sufficient strength. That is, it is characterized by joining by electron beam welding using nickel as a filler material.

After joining, the whole part of the body is ground to a predetermined diameter, and the cutting edge part 5 and the spiral groove 6 are machined to complete the small diameter drill shown in FIG. 1. The spiral groove 6 is continuously carved from the diamond sintered body part 21 and the cemented carbide part 22 of the PCD chip 20 to the drill body part 41 of the cemented carbide member 4°.

[For production]

In the joining structure shown in FIG. 6, if the rear end of the PCD chip 20 and the tip of the carbide member 40 are both perpendicular to the axis, there will be no collapse after joining. Even if the tip 20 falls down to some extent, damage to the tip 21 is extremely rare because the tip 20 is short. Misalignment between the chip 2o and the =7- body 41 at the joint portion 43 can be kept to a minimum using a jig to be described later.

As a result, the machining allowance expected for the diameter of the PCD chip 20 can be handled by the lessee, and the machining amount can be reduced as shown in Fig. 8 (
There are very few in comparison. In addition, the carbide member 40 is accurately l8
If the PCD chip is machined, by applying a steady rest to this part, there is no risk of breakage and sufficient grinding pressure can be applied for processing the PCD chip part.

The configuration shown in FIG. 6 in which the PCD chips 20 are bonded as described above is much more effective in the processing process after bonding than the configuration in FIGS. 7 and 8 in which the PCD blank 30 in FIG. 5 is used! Although advantageous, the conventional joining method using silver brazing has the above-mentioned drawbacks and has not been put into practical use. The present invention puts this configuration into practical use by electron beam welding using nickel as a filler material.

First, since the electron beam concentrates high energy in a very small local area, the temperature of only the joint 43 rises in a short time and welding is completed, and the diamond sintered body 21 at the tip of B- becomes overheated. There is no.

Second, since welding is carried out in a vacuum, no flux is required, and there are no defects such as foreign objects or bubbles in the welded area, and a sound solution can be formed.

In addition to the above effects, thirdly, by using nickel as a filler metal, sufficient welding strength can be obtained.

The table below shows an example of welding strength measurement using the bending test method.

The test piece is a round bar with a diameter of 2 m, and the value is the value at break of the load applied to the center of the fulcrum with a distance between fulcrums of 30.

The left column of the table shows the case where a load is applied to the welded part of a test piece made of a single piece of cemented carbide, and the right column made of the same material and the same dimensions, but electron beam welded with nickel as filler material in the center. Combining the five measurements, it can be seen that the strength of the welded part is the same as that of a single piece of cemented carbide.

〔Example〕

The PCD chip 20 having the configuration shown in FIG. 6 can be obtained by cutting the blank 30 shown in FIG. The best method for this is wire electrical discharge machining. P in Figure 3
CD blanks 10 are manufactured in large quantities to meet demand as materials for cutting tools and various types of milling cutters, so quality and
This is because the supply is stable.

Furthermore, since a large number of chips 20 can be obtained from one blank 10, it is also economical.

It is not difficult to manufacture the cemented carbide member 40 so that the drill body portion 41 and the shank portion 42 are accurately aligned. Further, the semi-finished product of the lumer type carbide drill shown in FIG. 2, which is manufactured in large quantities, can also be used. PC if necessary
The end faces of both the D-chip 20 and the carbide member 40 to be joined are polished perpendicular to the axis.

The chuck 60 shown in FIG.
0, and place the PCD chip 20 on the filler metal nickel plate 61 between them. The copper jig 62 is a PCD chip zO
is positioned at the base of the carbide member 40, and at the same time, a light pressure P is applied. That is, the jig 62 is supported by a support device (not shown) that allows vertical movement while keeping the jig 62 open to the chuck 60.

If the above-described configuration is placed in a vacuum of an electron beam welding device and the electron beam 63 is irradiated to focus on the joint 61, welding is completed in an instant. Since the copper positioning jig 62 is in contact with the diamond sintered body portion 21 of the PCD chip 20, heat flows into the jig 62 and also helps prevent the diamond sintered body from overheating.

By arranging a large number of the configurations shown in FIG. 9 on a circumference or in a straight line and sequentially sending them to the electron beam irradiation position, a large number of welds can be performed in succession without breaking the vacuum.

〔Effect of the invention〕

The present invention has made a significant contribution to the electronics industry and the like in that it has enabled the industrial and economical supply of small-diameter PCD drills, which had been desired with the expectation of long life but had not been realized.

It is clear that the gist of the present invention can also be applied to a small diameter drill whose cutting edge is a CBN sintered body.

[Brief explanation of drawings]

Fig. 1 is a side view showing an example of a small diameter drill manufactured by the manufacturing method according to the present invention, Fig. 2 is a side view of a conventional small diameter drill, Fig. 3 is a perspective view of a general PCD blank, and Fig. 4 is a side view showing an example of a small diameter drill manufactured by the manufacturing method according to the present invention. Figure 3 is a perspective view of a PCD chip cut out from the blank, Figure 5 is a perspective view of a conventional PCD blank for a small diameter drill, and Figure 6 is a PCD chip shown in Figure 4 bonded to a cemented carbide member. 7 is a cross-sectional view of the configuration using the PCD blank shown in FIG. 5, FIG. 8 is an exaggerated cross-sectional view of the state in which the PCD blank is inserted into the hole of the shank, and FIG. It is an explanatory view showing an example. 20... PCD chip 40... Carbide member 60° 62... Jig 63... Electron beam q diagram

Claims (3)

[Claims] (1) A diamond sintered body forming the tip of the drill,
Next, a PCD tip with a length of 3 mm or less consisting of a cemented carbide part that forms a small portion of the tip of the drill body is attached to the cemented carbide member that is integrated with the majority of the drill body and the shank, using nickel as a filler material. A method for manufacturing a small diameter drill characterized by electron beam welding. (2) Claim 1, characterized in that a PCD chip is made by cutting out small cylinders perpendicular to the plate surface from a plate-shaped PCD blank in which a diamond sintered body layer is lined with cemented carbide. A method for manufacturing a small diameter drill as described in Section. (3) The method for manufacturing a small-diameter drill according to claim 1 or 2, characterized in that the drill tip portion is made of a CBN sintered body.