JPS6157123B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method for manufacturing a carbide drill suitable for high-speed, high-feed drilling.

In general, carbide drills have cutting edges made of cemented carbide, which is harder than high-speed steel, so they can perform drilling at higher speeds than high-speed steel drills. This has the advantage that processing efficiency can be improved.

However, it has been difficult to improve the feed rate. This is because while cemented carbide is hard, it is also brittle, so there is a risk that the part near the axis of the drill tip will be crushed by the thrust load acting there.If you try to use a high feed rate, the thrust load will increase accordingly. , the risk of crushing will further increase. Therefore, with this type of carbide drill, there are certain limits to improving the efficiency of drilling, and it is difficult to say that it is fully satisfactory in terms of service life.

Therefore, in order to reduce the risk of crushing in the vicinity of the axis, it may be possible to manufacture a cemented carbide drill using a cemented carbide with higher toughness. However,
Although such a carbide drill can increase the feed rate, since the hardness of the cemented carbide, which is rich in toughness, is low, cutting speed is forced to decrease, so it is not a fundamental solution. Ta.

Taking the above points into consideration, the inventor of this application developed a new carbide drill as shown in FIGS. 1 to 7 as a drill capable of performing high-speed, high-feed drilling.

The carbide drill shown in FIGS. 1 to 3 has a drill body 1 having a two-layer structure.
is a central part 1 with a circular cross section centered on its axis O.
a, and a cylindrical outer peripheral portion 1b provided outside the central portion 1a. Center 1
a is made of a cemented carbide that has higher toughness than the cemented carbide that makes up the outer peripheral part 1b, and the outer peripheral part 1b is made of a cemented carbide that is harder than the cemented carbide that makes up the center part 1a. has been done. In addition, the center 1
The diameter d of a is set to D/15≦d≦D/5, where D is the outer diameter of the drill, and is smaller than the core thickness of the drill. Therefore, the chip discharge groove 2 and the cutting edge 4 are formed only on the outer peripheral portion 1b, and the chisel 5 is formed on the central portion 1a. Moreover, in the outer peripheral part 1b existing between the chip discharge groove 2 and the center part 1b,
Thinning is performed so that the cutting edge 4 comes into contact with the outer periphery of the center portion 1a. In addition,
Reference numeral 3 in the figure is a tip flank.

Furthermore, in the carbide drill shown in FIGS. 4 and 5, the axis O of the above-mentioned drill matches the center line 1 of the center portion 1a, whereas the center line 1 of the center portion 1a
The center line 1 of the drill is shifted from the axis O, and the drill shown in FIGS. 6 and 7 has a center portion 1a having a circular cross-sectional shape. The rest of the configuration is the same as the drill described above.

In addition, in the above drill, the entire drill is 2
Although it has a layered structure, only the blade part has a two-layer structure made of cemented carbide, and the shank may be made of steel.

According to the above-mentioned carbide drill, the outer peripheral part 1b where the cutting edge 4 is formed is made of a highly hard cemented carbide, and the central part 1a where the chisel 5 is formed and where a large thrust load acts is made of a hard metal. Since it is made of a highly durable cemented carbide, it can perform high-speed and high-feed drilling.

By the way, when manufacturing the above carbide drill,
Particularly problematic is the joining between the central portion 1a and the outer peripheral portion 1b. That is, the center part 1a and the outer peripheral part 1
b, for example, by brazing, the low layer is eroded by the workpiece or chips during drilling, and a gap corresponding to the low layer is formed between the center portion 1a and the outer peripheral portion 1b. . Uncut parts and chips from the workpiece repeatedly enter and fall off into this gap, resulting in damage to each joint surface between the center portion 1a and the outer peripheral portion 1b. Also, it is possible to press fit the center part 1a into the center part 1a inside the outer peripheral part 1b, but since the center part 1a is thin, it is difficult to press fit, and there is a risk that the center part 1a will break when press-fitted. The problem is that it is very high. Furthermore, in order to press-fit, it is necessary to finish the inner diameter of the outer circumferential portion 1b and the outer diameter of the center portion 1a with high precision, which poses problems such as the machining thereof being time-consuming. Note that if the fitting is relatively loose, cracks in the outer circumferential portion 1b can be eliminated, but there is a risk that the center portion 1a may fall off from the outer circumferential portion 1b.

This invention was made in consideration of the above-mentioned circumstances, and it is possible to firmly join the center part and the outer peripheral part without any gap. It is an object of the present invention to provide a method for manufacturing a carbide drill that can prevent the drill from falling off and can be easily manufactured.

Hereinafter, the manufacturing method of the present invention will be explained in detail.

[First Manufacturing Method] In this manufacturing method, as shown in FIG. 8, a cylindrical body 11 made of a green compact of cemented carbide is first manufactured. In this case, the columnar body is compression molded in advance,
The center portion of the columnar body may be hollowed out to form the cylindrical body 11, or the cylindrical body 11 itself may be obtained by compression molding. Note that a recessed portion that will become a chip discharge groove when completed as a drill may be formed in advance on the outer periphery of the cylindrical body 11. In this way, since the rod-shaped body 11 can be smaller than the inner diameter of the cylindrical body 10, the rod-shaped body 11 can be easily inserted into the cylindrical body 10, and the rod-shaped body 11 can be easily inserted. There is no.

Next, the rod-shaped body 12 is inserted into the cylindrical body 11.

This rod-shaped body 12 is made by compression molding a cemented carbide that has higher toughness than the cemented carbide forming the cylindrical body 11 and has a smaller shrinkage rate during sintering. The outer diameter of the rod-shaped body 12 should be determined by considering the difference in the amount of shrinkage between the cylindrical body 11 and the rod-shaped body 12 after sintering.
It is best to make the inner diameter 0.01 to 0.5 mm smaller than the inner diameter.

Thereafter, the rod-shaped body 12 is assembled into the cylindrical body 11 and then sintered. Then, the cylindrical body 11
shrinks more than the rod-shaped body 12, so that the fit between them becomes a tight fit. Moreover, they are metallically bonded to each other during sintering. Thereby, the cylindrical body 11 and the rod-shaped body 12 are firmly integrated without any gaps.

Next, as shown in FIG. 9, the sintered body is processed into a chip discharge groove 13, a cutting edge 14, and other shapes necessary for a drill. Regarding this shape processing,
It may be performed before sintering and then sintered.

Note that the entire drill may be manufactured as described above, or only the blade portion may be manufactured.

[Second Manufacturing Method] This manufacturing method differs from the first manufacturing method in that the rod-shaped body is sintered in advance, and the other steps are the same as the first manufacturing method.

In this second manufacturing method, since the rod-shaped body is sintered in advance, when the assembled cylindrical body and the rod-shaped body are sintered, the rod-shaped body does not shrink.
Only the cylindrical body contracts. Therefore, in this second manufacturing method, there is no need to consider the difference in shrinkage rate between the cemented carbide forming the rod-shaped body and the cemented carbide forming the cylindrical body. Moreover, since the rod-like body hardly shrinks, the rod-like body and the rod-like body can be integrated even more firmly. Further, since the rod-shaped body is sintered in advance, accidents such as breakage of the rod-shaped body during the manufacturing process can be prevented, thereby reducing the loss rate.

[Third manufacturing method] In this third manufacturing method, a cemented carbide having higher toughness than the cemented carbide constituting the outer periphery and having a smaller shrinkage rate during sintering is placed in the center. In this method, a rod-shaped green compact is produced by simultaneously compression molding the outer circumferential portion and the green compact, and then this green compact is sintered and then shaped. Note that, as in the first and second manufacturing methods described above, the shape processing step and the sintering step may be reversed.

In this third manufacturing method, the compression molding process and the sintering process only need to be performed once, so the carbide drill can be manufactured at a lower cost compared to the above two manufacturing methods, and it is especially suitable for mass production. Suitable for cases where

As explained above, according to the method for manufacturing a cemented carbide drill of the present invention, in any of the first, second, and third methods, the cemented carbide is formed at the center and the outer periphery of the drill during sintering. It is integrated by utilizing the property of shrinkage, and since the center and the outer circumference are joined metallically during sintering, the center and the outer circumference can be firmly joined without any gaps. It is possible to prevent the center part and the outer periphery from being damaged and the center part from falling off from the outer periphery, and since there is no need to press fit the rod-shaped body, it is possible to prevent the rod-shaped body from breaking, and it is easy to manufacture. Effects such as being able to do this can be obtained.

[Brief explanation of the drawing]

1 to 3 show an example of a carbide drill developed by the inventor of this application, FIG. 1 is a front view thereof, FIG. 2 is a partially omitted side view, and FIG. 3 is the same as that shown in FIG. 1. - A sectional view taken along the line, FIGS. 4 and 5 show other examples of the carbide drill, FIG. 4 is a front view thereof, FIG. 5 is a partially omitted side view, and FIGS. 6 and 7. shows yet another example of a carbide drill; FIG. 6 is a front view thereof, FIG. 7 is a partially omitted side view, and FIGS. 8 and 9.
The figures are diagrams for explaining the manufacturing method of the present invention, in which Figure 8 is a perspective view showing the assembly process, and Figure 9 is a perspective view showing the assembly process.
The figure is a partially omitted side view showing the carbide drill after shape processing. 1... Drill body, 1a... Center part, 1b...
Outer peripheral part, 11... cylindrical body, 12... rod-shaped body, O...
...Axis line, 1...Center line.

Claims (1)

[Claims] 1. A cylindrical body that is a compacted powder body of cemented carbide having an insertion hole that includes the axis of the drill and is formed away from the portions of the drill that are to become the two chip discharge grooves;
It has higher toughness than the cemented carbide that makes up this cylindrical body,
A rod-shaped body made by compression molding a cemented carbide with a small shrinkage rate during sintering is inserted and assembled, and then either one of the assembled cylindrical body and rod-shaped body is shaped and sintered. A method for manufacturing a carbide drill, characterized by performing one step and then performing the other step. 2. A cylindrical body that is a cemented carbide powder body that includes the axis of the drill and has an insertion hole that is formed away from the parts that are to become the two chip discharge grooves of the drill,
A rod-shaped body made by compression molding and sintering a cemented carbide that has higher toughness than the cemented carbide that makes up the cylindrical body is inserted and assembled, and then the assembled cylindrical body and rod-shaped body are shaped. 1. A method for manufacturing a carbide drill, comprising performing either one of and sintering, and then performing the other. 3. A cemented carbide that has higher toughness than the cemented carbide and has a smaller shrinkage rate during sintering than the cemented carbide that forms the outer periphery in the center part that includes the axis of the drill and is away from the parts that should become the two chip discharge grooves of the drill. The alloy is arranged, the center and the outer periphery are compression-molded at the same time to form a rod-shaped green compact, and then one of the shaping of the green compact and sintering is performed, and then the other is performed. Characteristic manufacturing method for carbide drills.