JPS5943247B2 - Surface-coated cemented carbide miniature drill - Google Patents

Description

Detailed Description of the Invention The present invention significantly extends the service life of a miniature drill made of cemented carbide by coating each surface of the margin and flute parts of the drill body with a hard coating layer with excellent wear resistance. This relates to a miniature drill made of surface-coated cemented carbide.

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

When forming a small hole with a diameter of 2u or less, the strength, precision, and processing conditions of the drill cannot be considered in the same way as ordinary drilling, so a drill for forming such a small hole is called a miniature drill. 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 different diameter than the drill body B, as shown in FIG.
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, but stepped miniature drills are strong and have high installation accuracy, so they have become widely used for various objects. .

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.
A cutting blade 3 is provided at each edge at a symmetrical position on one side following the flute portion 2, and between this cutting blade 3 and the ridge line there is a most flank surface 4, and following this most flank surface 4, there is a ridge line. A second flank face 5 is formed at a position beyond the margin, and both side faces 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 viewpoint, the inventors of the present invention aimed to manufacture a miniature drill with a significantly extended service life (as a result of various studies, the present inventors found that carbides and nitrides of metals in Groups 4a, 5a, and 6a of the periodic table were used). , carbonitride, carbonate, carbonitride, aluminum oxide, and a hard coating layer consisting of a single layer or a multilayer of two or more types selected from the group consisting of solid solutions of two or more of these types, In combination with a cemented carbide miniature drill, the wear resistance and welding resistance can be significantly increased and the life of the miniature drill can be extended, and the thickness of the hard coating layer is 0.5 to 2.
The effect is most excellent when the thickness is in the range of 0 μm, and the hard coating layer is applied to the drill body of the miniature drill, which is the part that most affects hole accuracy and chip disposal during work with the miniature drill. It was discovered that by providing the hard coating layer only on the margin and flute parts, the effect of extending the life of the miniature drill is almost as good as when the hard coating layer is provided on the entire surface of the miniature drill body. .

Therefore, this invention was made based on the above knowledge, and the surfaces of the margin part and flute part of the drill body of a miniature drill made of cemented carbide are
A layer thickness of 0.5 to 0.5 to 0.5 to 100%, consisting of a group consisting of carbides, nitrides, carbonitrides, carbonates, and carbonitrides of metals of Groups a, 5a, and 6a, and aluminum oxide, as well as solid solutions of two or more of these. By coating with a hard coating layer of 20μm, the cutting speed is high, and the wear due to the burnishing effect with the rigid material is significant, and this wear causes a decrease in machining dimensional accuracy and an increase in cutting resistance. It protects the margin area around the main body and prevents chips from welding to the flute section and hindering the smooth discharge of chips, thereby maintaining good hole machining accuracy over a long period of time and extending the service life. This is a unique feature of miniature drills that has made it possible to significantly extend the life of the drill.

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 may not be obtained. 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 form a hard coating layer only on the margin and flute areas, when forming the coating layer using the above method, it must be brought into close contact with areas other than the margin and flute areas, and the hard coating layer should be kept at the coating treatment temperature. A protective plate made of a material that does not deform, such as graphite, oxide, super hard metal, nitride ceramics, or metal, may be installed.

Furthermore, even if the entire surface of the drill body is coated, the coating layer other than the margin and flute areas may be removed by some means without changing the effectiveness. If parts other than the margin part and the flute part are coated, the effect will not be adversely affected even if used as is.

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

Example 1 First, a miniature drill (hereinafter referred to as a comparative miniature drill) made of cemented carbide of ISO usage classification P30 and having a 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 surfaces of the margin and flute parts of the drill body of the comparative miniature drill were covered with stainless steel plates except for those parts, and heated to a reaction temperature of 1000°C in a surface coating treatment furnace using a normal chemical vapor deposition method. te, TiC1
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. As shown in FIG. 5a, a side view of the main part, and FIG. A coated miniature drill of the present invention was manufactured.

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: 2220 m, 7 m1n.

Feed: 0.05 mrrt/rev, Machining hole diameter: LOmmφ, Machining hole depth: 4. A cutting test was conducted under the conditions of (without cutting oil) and the number of holes drilled over the life of the miniature drill was 45,000.
(15,000 shots) The life of the drill was reached due to an increase in cutting force after drilling, whereas the comparative miniature drill reached the end of its life after drilling.
00 (10,000 shots) The life has come to an end due to dimensional defects and increased cutting resistance after hole drilling.

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.

It is clear from this result that a significantly longer cutting life can be ensured if the hard coating layer is present in the margin and flute portions.

Example 2 The same comparison miniature drill used in Example 1 was placed in a vacuum container, the temperature of which was maintained at 400°C, and A
While introducing a mixed gas of r and N2, the atmospheric pressure was increased to 2.
The margin of the comparative miniature drill was determined by a sputtering method under the conditions of applying a voltage of 3 to 1 to the target Ti plate so as to be negative relative to the wall of the vacuum chamber and holding it for 2 hours. A miniature drill of the present invention was manufactured by forming a TiN layer with a thickness of 2 μm on the surfaces of the flute portion and the flute portion.

At this time, areas other than the margin portion and the flute portion surface were covered with a graphite protective layer.

Next, regarding the miniature drill of the present invention obtained by this coating treatment and the same comparative miniature drill as that in Example 1, the work material was Niglass epoxy resin, thickness 1.6 mm (G10
equivalent), 3 sheets stacked, cutting speed: 160m/mVL, feed: 0.05mm/rev 0, machined hole diameter: 1. A cutting test was conducted under the following conditions: Ommφ, hole depth: 4.8 mm, no cutting oil, and the number of holes drilled over the life of the miniature drill of the present invention was 4500.
After drilling 0 (15,000 shots), the life span was reached due to wear of the margin part, but there was almost no welding of cutting chips to the flute part, and there was no chipping.

On the other hand, most of the comparative miniature drills have 30,000 (1,000
0 shot) Hole machining reached the end of its life, and the remaining ones had chips due to welding of cutting chips to the flute part, and their lifespans were even shorter.

As mentioned above, the miniature drill of the present invention has the surfaces of the margin part and the flute part coated with a hard coating layer, so the margin part has excellent wear resistance and the flute part has excellent wear resistance. It has welding properties, so when using it, it is possible to machine holes with high precision, and it is extremely useful as it does not cause smearing, eliminates drill breakage accidents, and ensures an extremely long drill life. It has certain characteristics.

[Brief explanation of drawings]

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 surfaces of the margin part and the flute part, and FIG. In the drawings, A...Shank part, B...
...Drill body, 1... Chisel edge part, 2.
... Flute part, 3 ... Cutting blade, 4 ...
...First flank, 5...Second flank, 6...
...Margin section, 7...Relief section, 8.
...Hard coating layer.

Claims (1)

[Claims] 1. Each surface of the margin part and flute part of the drill body of the cemented carbide miniature drill is determined according to 4a of the periodic table,
5a and 6a group metal carbides, nitrides, carbonitrides, carbonates, carbonate nitrides, aluminum oxide, and solid solutions of two or more of these. Layer thickness 0 consisting of multiple layers of seeds or more
．． A surface-coated cemented carbide miniature drill characterized by being coated with a hard coating layer of 5 to 20 μm.