JPS5943246B2 - Surface-coated cemented carbide miniature drill - Google Patents

Description

Detailed Description of the Invention This invention significantly extends the service life of a miniature drill made of cemented carbide by coating the entire drill body or the entire drill body excluding the flank surface with a hard coating layer with excellent wear resistance. This article relates to a miniature drill made of surface-coated cemented carbide that has been designed to improve the surface coating.

Conventionally, a miniature drill is generally used as a cutting tool when forming a small diameter hole of 2 mw or less in diameter in a printed circuit board or a metal material such as steel or cast iron.

When forming a small hole with a diameter of 2 mm or less, the strength, precision, and processing conditions of the drill cannot be considered in the same way as normal drilling, so a drill for forming such a small hole is called a miniature drill. However, there are two types of miniature drills: a straight shank drill whose shank has the same diameter as the drill body, and a stepped drill whose shank portion A has a diameter different from the drill body B as shown in Fig. 1.
Depending on the shape of the drill body B, there are two types: a straight type as shown in a side view in FIG. 2, and an undercut type as shown in a side view in FIG.

Straight shank miniature drills are inexpensive, but
Small-diameter drills are difficult to chuck and have poor accuracy (in contrast, stepped miniature drills have high strength and high installation accuracy, so they have become widely used for various objects. Ta.

Note that FIG. 1a is a side view of the stepped drill, and the first
The figure is a front view of the drill body viewed from the cutting edge.

In each of these conventional miniature drills, as shown in the front view of the main part of the drill body in FIG. 4, a flute part 2 is formed sandwiching a chisel edge part 1 at the top.
Continuing from this flute part 2 (each edge is symmetrically located on one side, a cutting blade 3 is provided, and between this cutting blade 3 and the ridge line, there is a first flank 4, and following this most flank 4, there is a ridge line). A second flank face 5 is formed at a position beyond the width of the second flank, and both sides have a structure consisting of a margin part 6 with a predetermined margin width and a relief part 7 following this, It is made of cemented carbide manufactured by normal powder metallurgy.

On the other hand, in recent years, workpieces that require machining with such miniature drills have been manufactured using multilayered materials that are made by laminating many layers of glass cloth and resins such as epoxy, triazine, and resin in consideration of heat resistance and moisture resistance. With the rapid increase in the number of printed circuit boards and materials that are difficult to cut, such as stainless steel, the use of conventional miniature drills such as those mentioned above suffers from severe wear and welding of chips and other cutting debris. Lifespans inevitably become shorter.

The lifespan of such a miniature drill is determined based on factors such as increased thrust due to chisel edge wear and flank wear of the drill body, deterioration of hole accuracy due to chisel edge wear and margin wear, and loss of power due to wear on the outer edge of the cutting edge. This is caused by an increase in drilling noise due to wear on the outer edge of the cutting edge and wear on the margin, a constant wear amount, and an increase in thrust and damage to the drill due to welding of cutting chips to the flute.

Therefore, in order to extend the service life of miniature drills, it is necessary to take measures to suppress the wear of the various parts of the drill body and prevent cutting chips from welding to the various parts of the drill body, but there are still no effective measures. At present, no concrete means have been found.

From the above-mentioned point of view, the present invention provides a drill body that includes the margin section, flute section, and relief section, or flank surface, which are parts that greatly affect hole accuracy and chip disposal and have a significant impact on the life of the drill. The entire surface of the drill body, or the entire surface of the drill body, with the exception of the flank surfaces (including the first and second flanks), which have a relatively small effect on the life of the drill and can be recovered with a little polishing, are This product provides a miniature drill that has abrasion resistance and a property that prevents cutting chips from welding, thereby extending its service life. The entire surface of the drill body except for the periodic table is 4a, 5a,
and 1 selected from the group consisting of carbides, nitrides, carbonitrides, carbonates, and carbonitrides of group 6a metals, aluminum oxide, and solid solutions of two or more of these.
Layer thickness of 0.5~ consisting of a single layer of seeds or multiple layers of two or more types
By coating with a 20μm hard coating layer, we aim to improve the wear resistance of each part of the drill body and the welding resistance against cutting chips, maintain good hole machining accuracy over a long period of time, and prevent chips from being removed especially from the flute section. This is a miniature drill made of surface-coated cemented carbide that can be discharged smoothly and has a significantly extended service life.

In addition, in the miniature drill of the present invention, coating the shank portion with the above-mentioned coating layer has no particular direct effect on the hole forming performance, but due to the coating process of the miniature drill, the shank portion may also be coated. There are times when it is advantageous to let things fall by the wayside.

Therefore, the miniature drill of the present invention may have its shank portion covered with the above-mentioned coating layer, and even if the shank portion is not covered with such a coating layer, it does not deviate from the present invention. do not have.

In addition, in the miniature drill of the present invention, the layer thickness of the hard coating layer is limited to 0.5 to 20 μm, because if the layer thickness is less than 0.5 μm, the desired wear resistance improvement effect and welding resistance improvement effect can be achieved. On the other hand, 20
This is because even if the layer thickness exceeds .mu.m, the wear resistance and welding resistance will not improve much, and on the contrary, the toughness of the drill body will decrease.

The hard coating layer in the miniature drill of the present invention can be formed by a common surface coating treatment method such as a chemical vapor deposition method, an ion blasting method, or a sputtering method.

In order to prevent the flank surface of the drill body from being coated, when forming the coating layer using the method described above, it is necessary to use a material such as graphite, oxide, or super-hard alloy that does not deform at the coating treatment temperature. Install a protective plate made of materials such as nitride-based ceramics or metal, or polish only the flanks of the drill body whose entire surface is covered with a coating layer to remove the coating layer in that area. Just try to remove it.

Next, the miniature drill of the present invention will be explained through examples and in comparison with comparative examples.

EXAMPLE First, a miniature drill (hereinafter referred to as a comparative miniature drill) made of cemented carbide according to the ISO classification P30 and having the shape shown in FIGS. 1 and 2 and a front view of the main part shown in FIG. 4 was prepared.

On the other hand, the entire surface of the comparative miniature drill including the shank and drill body was coated with TiCl4 in a surface coating treatment furnace at a reaction temperature of 1000°C using a normal chemical vapor deposition method.
By conducting coating treatment for 3 hours while introducing a mixed gas having a composition of: 3% by volume, 37% by volume for N2, and 60% by volume for N2, a TiN layer with a layer thickness of 5.0 μm was formed. A miniature drill of the present invention was manufactured in which the entire surface of the miniature drill was covered with a hard coating layer 8, as shown in FIG. 5a, a side view of the main part, and FIG. 5, a front view of the main part.

Next, regarding the miniature drill of the present invention obtained by this coating treatment and the comparative miniature drill described above, the workpiece material was Niglass epoxy resin, thickness 1.6 mm (G10
Cutting speed: 220m/m Sail feed: 0.0511!711/rev 0, Machining hole diameter = 1.0 mm φ, Machining hole depth = 4.8 mm, Cutting fluid: None, A cutting test was conducted under the following conditions and the number of holes drilled over the life of the miniature drill of the present invention was 4800.
0 (16,000 shots) The life of the drill was reached due to an increase in cutting force after drilling, whereas the comparative miniature drill had a life of 30 shots.
000 (10,000 shots) The life has come to an end due to poor hole diameter dimensions and increased cutting resistance.

When observing the flute section of the comparison miniature drill that had reached the end of its service life, a large amount of welded chips was observed.

Next, the flank surfaces 4 and 5 of the miniature drill of the present invention after the use described above were re-polished with an appropriate re-polishing allowance, and a side view of the main parts is shown in Fig. 6a, and a front view of the main parts is shown in Fig. 6. As shown in the figure, the flank surfaces 4 and 5 were exposed to the cemented carbide.

When this regrinded miniature drill was subjected to a cutting test under the above conditions, it reached the end of its life after drilling 45,000 (15,000 shots) holes due to an increase in cutting resistance. It is clear that a significantly longer cutting life can be ensured if the layer is present.

As mentioned above, the miniature drill of the present invention has at least the entire surface of the drill body or the entire surface of the drill body other than the flank surface covered with a hard coating layer.
It has excellent wear resistance and welding resistance, so when using it, it is possible to machine holes with high precision, and there is no smear, eliminating the risk of drill breakage, and making it possible to use extremely long drills. It has extremely useful properties such as ensuring a long life.

[Brief explanation of the drawing]

Figure 1 shows a schematic diagram of a miniature drill, Figure a is its side view, Figure 2 is its front view, Figure 2 is a side view of the main parts of a straight type miniature drill, and Figure 3 is an undercut type. Figure 4 is a side view of the main parts of the miniature drill, Figure 4 is a front view of the main parts of the miniature drill, and Figure 5 is a front view of the main parts of the miniature drill.
The figures show the main parts of the miniature drill of the present invention, which has a coating layer on the entire surface, and FIG. Another embodiment of the miniature drill of the invention is shown, in which FIG. 1A is a side view of the main part thereof, and FIG. In the drawings, 1... chisel edge part, 2... flute part, 3... cutting edge, 4...
First flank, 5...Second flank, 6...
・Margin part, 7... Relief part, 8...
...Hard coating layer, A...Shank part, B...
...Drill body.

Claims (1)

[Claims] 1. At least the entire surface of the drill body or the entire surface of the drill body excluding the flank surface of a miniature drill made of cemented carbide is treated with carbides, nitrides, carbonitrides, carbonates, and Covered with a hard coating layer with a layer thickness of 0.5 to 20 μm consisting of a single layer or a multilayer of two or more types selected from the group consisting of carbonate nitride, aluminum oxide, and a solid solution of two or more of these types. A miniature drill made of surface-coated cemented carbide.