JPS61152308A - Small-sized twist drill made of hard sintered material - Google Patents

Abstract

PURPOSE:To permit the boring with high quality for a long period by using a small-sized twist drill by improving the radiation of cutting heat by using a shank material having a thermal conductivity over 0.1cal/m.sec. deg.C. CONSTITUTION:A hard sintered part 21 is made of diamond powder in 85wt% and WC-15%Co as the rest, and a supporting part 22 is made of WC-12%Co, and a cylindrical body 23 which is made of composite sintered material and has a diameter of 0.7mm and a length of 15mm is brazed into the hole 26 on a shank 25 and fixed. Then, a small-sized twist drill is formed by working a cutting tip and a cutting groove. Said shank 25 is made of superalloy, and the material which contains WC-6% or WC-15%TiC-6%Co is used, and the thermal conductivity is 0.1cal/cm.sec. deg.C or more, and the hardness is over 25HRc. Since the heat generation at the cutter tip is dispersed through the shank 25, high-speed revolution is permitted, and the life of the cutter tip can be prolonged.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application The present invention is a method of embedding a cylindrical body of a composite sintered material having a hard head in a shank made of cemented carbide, etc. The blade attachment relates to a hard sintered compact small-diameter drill that is made into a drill by processing the blade groove.

More specifically, the present invention provides a small diameter sintered body comprising a hard head such as a diamond sintered body or a high-pressure phase boron nitride sintered body, and a support part formed integrally with the head and made of, for example, a cemented carbide. A cylindrical body of composite sintered material is pushed into a hole formed at one end of a shank made of cemented carbide, etc., and after being fixed by a method such as brazing, the cylindrical body of composite sintered material is machined with a tip and a groove. This invention relates to a small-diameter hard sintered compact drill that has been made into a drill.

BACKGROUND OF THE INVENTION Drills made of cemented carbide are widely used for drilling holes in metal and non-metal materials. In particular, cemented carbide drills with a diameter of about III] II1 are used for drilling holes in printed circuit boards, for which the demand has been increasing rapidly in recent years.

Various materials are used for printed circuit boards, but the main one used is a reinforced resin made by impregnating glass fiber with epoxy resin, which is generally referred to as a glass-evo board.

Drilling of such printed circuit boards is usually done using a highly rigid drill at a rotation speed of 50,000 to 60,000 rpm, but the glass fibers contained in the board wear out the carbide tool very quickly, and generally A carbide drill reaches the end of its lifespan after 3,000 to 5,000 hits (hits refers to the number of holes drilled). These drill machines are equipped with an automatic tool changer, and the drill that has reached the end of its service life is automatically replaced.However, in order to improve production efficiency, the time required for automatic tool change is also an issue, and the life of the drill is reduced. There is a strong desire to reduce the number of tool changes, that is, the tool change time.

Looking at the characteristics of printed circuit boards, there is a strong demand for higher functionality by further improving heat resistance, etc., and although it is actually possible to manufacture such board materials6, in general, such high-performance materials are It is difficult to cut, and the lifespan of conventional ultra-hard drills is extremely short, so the reality is that this type of substrate material cannot be put to practical use.

Furthermore, it is desired to increase the rotational speed of the drilling drill in order to drill even more efficiently into ordinary glass epoxy substrates, but this also means that the lifespan of conventional cemented carbide drills rapidly decreases as the cutting speed increases. Since this decreases, it is not possible to achieve high efficiency by increasing the drill rotation speed.

On the other hand, sintered diamond tools, whose usage has been rapidly increasing in recent years, have significantly higher hardness and wear resistance than carbide tools, and are extremely useful when cutting the above-mentioned reinforced resins. Demonstrates high performance.

However, as shown in FIG. 1, this sintered diamond tool holds as a chip a composite sintered body 13 in which a sintered diamond layer 11 is bonded to a support portion 12 of cemented carbide. When manufacturing a drill using this composite sintered body 13, the composite sintered body 13 must be fixed to the tip of the shank 15 by some method as shown in FIG.

However, the diameter of the drill tip made from this composite sintered body 13 is generally about 1 mm, and if such a small diameter drill tip does not have a very strong bonding strength with the shank 15, it must be joined by grinding the cutting edge after bonding. It will come off from the part 16, making it impossible to manufacture a good drill. In particular, sintered diamond is difficult to grind and has high grinding resistance, and the strength of ordinary silver brazing is insufficient. For example, electron beam welding can be considered as a bonding method with high bonding strength, but if electron beam welding were to be implemented, the drill manufacturing process would be complicated and the cost would be high, making it difficult to meet the rapid increase in demand for high-performance drills in recent years. There wasn't.

As a means to solve this problem, as shown in FIGS. 3(a) and 3(b), a sintered diamond layer 21 is provided on the head, and a cylindrical support portion 22 with approximately the same diameter as the sintered diamond layer 21 is provided.
A composite sintered material cylindrical body 23 having a
), it was devised to embed it in one end of the shank 25 and to process the embedded cylindrical body 23 of composite sintered material with a blade and a groove. At this time, stainless steel was used for the shank body 25 due to ease of processing and prevention of rust.

However, when using a stainless steel shank, due to its low thermal conductivity, the cutting heat of the cutting edge during drilling will not be dissipated through the shank, which will increase the temperature of the cutting edge and adversely affect the quality of the hole wall, and the high speed Using rotation reduces the life of the cutting edge. Furthermore, when chaffing the shank portion during drilling, stainless steel has a problem of low hardness and scratches.

Problems to be Solved by the Invention The present invention aims to solve the above-mentioned problems of the prior art.More specifically, it is an object of the present invention to solve the problems of the prior art. To provide a small-diameter hard sintered drill which is an excellent drill and can drill high-quality holes for a long period of time by improving cutting heat dissipation by using a shank material with high thermal conductivity and hardness. It is in.

Means for Solving the Problems In order to achieve the above object, according to the present invention, a hard sintered part containing 50% or more of either diamond powder or high-pressure phase boron nitride powder, or both, and having a circular cross section. □ A composite sintered material comprising: a support part that has a cylindrical shape with approximately the same diameter as the hard sintered part and is joined to the hard sintered part at one end □ The support part of the cylindrical body is attached to the shank. A hard material obtained by pushing the composite sintered material into a hole formed at one end and having approximately the same diameter as the composite sintered material cylinder and fixing it. In a sintered compact small diameter drill, the shank has a thermal conductivity of 0.1 cal 7c
A hard sintered small-diameter drill is provided, characterized in that it is made of a material having a thermal conductivity of m'' sec, .degree. C. or more.

When the hard sintered part is sintered with diamond powder as the main component, diamond powder alone or 7
It is sintered with a binder containing 0% or more of diamond, with the remainder mainly composed of Fe, Co, or Ni. A preferable example of such a hard sintered part is 7
There is a sintered body of 0% or more diamond and WC-5 to 15% Co. When manufacturing a hard sintered part using diamond powder alone, the diamond powder is placed on a support such as cemented carbide, hot pressed, and the binder is infiltrated into the diamond powder from the support during hot pressing. It is better to force it.

When the hard sintered part is mainly composed of high-pressure phase boron nitride powder, the high-pressure phase boron nitride powder alone, or 50% or more of the high-pressure phase boron nitride and carbides, nitrides of group 4a, 5a, and 6a elements,
Some are sintered with carbonitride and aluminum and/or silicon added as binders. Note that the powder of high-pressure phase boron nitride alone does not require a binder, and sintering of the hard sintered part can be achieved by itself. Here, high-pressure phase boron nitride means cubic boron nitride and wurtzite boron nitride.

The supporting part of the composite sintered material cylinder is made of so-called cemented carbide, that is, carbide of elements of groups 4a, 5a, and 6a of the periodic table,
It is a sintered alloy or cermet made by bonding nitrides, carbonitrides, borides, silicides, or their mutual solid solution carbides with iron group metals such as Fe, Co, or N1. Cermet 1
An example is a carbide of (Mo, W) C bonded with an iron group metal of N1 or Co.

Still another support material is a sintered alloy called a so-called heavy metal, which contains 80 to 98% by weight of W and the remainder is Ni-Fe or Ni-Fe-Cu.

Further, according to one aspect of the present invention, as shown in FIG. 3(b), the hard sintered part 21 and the support part 22 of the cylindrical body of the composite sintered material are formed by an intermediate bonding layer having a thickness of 0.5 mm or less. They are joined via 24.

The intermediate bonding layer is made of less than 70% high-pressure phase boron nitride and the remainder is one of carbides, nitrides, carbonitrides, or borides of Ti, Zr, or Hf in group 4a of the periodic table, or a mixture thereof, or a mixture thereof. Preferably, the material is mainly composed of a solid solution compound, and the material contains 0.1% by weight or more of AI and/or Si.

Further, according to one aspect of the invention, the support may be composed of two or more layers of material in the axial direction.

As one such example, the supporting side layer of the second material layer is W
It is a C-Co sintered alloy, and the hard head side layer is (Mo,
W) Some are made of cermets in which C carbide is bonded with iron group metals such as Ni or CO.

The thermal conductivity of the shank material is 0.1cal 7cm-sec
, 't: Above, hardness HRc25 or more is desirable. Thermal conductivity is O, 1 cal/cm-sec,
Examples of the above metal materials include cemented carbide, W alloy, Mo alloy, copper, etc. Among these, those with hardness of HRc25 or more are cemented carbide, W alloy, and Mo alloy.

As a cemented carbide, WE'-Co alloy contains 5 to 15% Co.
Preferably. In addition, as a W alloy, W is 80 to 98
Contains weight%, the balance is Ni-Fe or Ni-Pe-C
A sintered alloy called a so-called heavy metal made of u is preferable, and an Mo alloy containing 60 to 90% by weight of Mo, with the balance being a copper-based alloy is preferable.

11 As a shank material, the thermal conductivity is 0. Stainless steel in the range of O1-0.2, high speed steel, WC-6%Co, WC-1
5% TiC-6% Co was prepared.

On the other hand, the hard sintered part is made up of 85% diamond powder and the rest is W.
It is made of C-15%Co, and the support part is WC-12%C.

A cylindrical body of composite sintered material with a diameter of 0.7 mm and a length of 15 mm is pushed into the hole at the end of the shank as shown in Figure 4(a), and after being fixed by brazing, the cutting edge and groove are A small-diameter drill having the shape shown in Fig. 4(b) was fabricated by processing.

After performing a drilling test on a printed circuit board using these small diameter drills, we evaluated the inner surface of the hole and found that the thermal conductivity was 0.
．． In small-diameter drills using shanks made of stainless steel or high-speed steel with a rating of 1 or less, roughness of the hole wall surface was observed, and seizure occurred frequently. Furthermore, the stainless steel shank was gripped by a tool during machining of the cutting edge and groove, resulting in scratches on the outer surface.

On the other hand, anal-6%Co or WC-15%TiC-6%C
In the case of the small diameter drill using the shank No. 1, the hole wall surface was cut beautifully, there was no seizure, and there were no scratches on the outer surface of the shank.

Effects of the Invention As detailed above (the present invention provides a composite sintered body comprising a hard sintered part containing diamond or high-pressure phase boron nitride, and a support part joined at one end of this hard sintered part) A hard sintered compact small-diameter drill obtained by fixing the supporting part of the cylindrical material to the shank and adding a straight or curved groove and a cutting edge to the cylindrical part of the composite sintered material has a thermal conductivity of 01 lcal.
7 cm-sec, - or more, preferably with a hardness of H
It is characterized in that the shank is made of a material with an Rc of 25 or more.

By using a shank made of a material with these characteristics, the cutting heat of the cutting edge during drilling is conducted and dissipated through the shank, preventing the temperature of the cutting edge from rising, and allowing for drilling of good quality hole walls. This makes it possible, and the life of the cutting edge does not decrease even when used at high speeds. Furthermore, by using a shank made of a material with high hardness, the shank surface is less likely to be damaged even if the shank portion is chucked during drilling, and a hard sintered compact small diameter drill with high commercial value can be provided.

[Brief explanation of the drawing]

FIG. 1 is a perspective view of a composite sintered body consisting of a sintered diamond layer and a cemented carbide support. FIG. 2 shows a state in which the composite sintered body shown in FIG. 1 is joined to a shank. FIGS. 3(a) and 3(b) show a cylindrical body of a composite sintered material used for producing the hard sintered small-diameter drill of the present invention. Fig. 4(a) shows the state in which the cylindrical body of the composite sintered material shown in Fig. 3 is fixed to the shank, and Fig. 4(b) shows the hard sintered material obtained by sharpening and cutting the blade groove. A compact small diameter drill is shown. (Main reference numbers) 11, 21...Sintered diamond layer, 12.22...
- Cemented carbide support part, 13.23... Composite sintered body, 15.25... Shank, 16... Joint part.

Claims (5)

[Claims] (1) a hard sintered part containing 50% or more of either diamond particles or high-pressure phase boron nitride particles and having a circular cross section, and a cylindrical shape having approximately the same diameter as the hard sintered part; The support part of the composite sintered material column, which has a support part joined to the hard sintered body part at one end thereof, is connected to a hole having approximately the same diameter as the composite sintered material column formed at one end of the shank. In a hard sintered compact small-diameter drill obtained by inserting and fixing the cylindrical body of the composite sintered material into a straight or curved groove and cutting the tip, the shank has a thermal conductivity of 0.1.
cal/cm・sec. - A hard sintered small-diameter drill characterized by being made of a material with a thermal conductivity of ℃ or higher. (2) The hard sintered small-diameter drill according to claim 1, wherein the shank has a hardness of HRc25 or more. (3) The hard sintered compact small diameter drill according to claim 1 or 2, wherein the shank is made of cemented carbide. (4) The hard material according to claim 1 or 2, wherein the shank contains 80 to 98% by weight of W, and the remainder is an alloy consisting of Ni-Fe or Ni-Fe-Cu. Sintered compact small diameter drill. (5) The hard sintered compact small-diameter drill according to claim 1 or 2, wherein the shank contains 60 to 90% by weight of Mo, and the remainder is a Cu-based alloy.