JPS59169707A - Drill - Google Patents

Abstract

PURPOSE:To prevent breakage of the cutting edge at the center of a drill by combining an extra-hard alloy, which suits to characteristics of the drill, complexly with the drill proper and solidly from the metallurgical point of view. CONSTITUTION:The body 2 of a drill 1 is formed by an extra-hard alloy, and the tip of the body has a small diameter approx. the same as thickness l of the web for a length comparative with the re-grinding amount of the drill, and a chisel 3 is fixed to the tip. A grinding part 4 to provide standard thickness for the tip web thickness according to necessity. Thereby it can stand with excessive thrust force sufficiently, as well as be secured with less likelihood of breakage of the central cutting edge and wear of the peripheral cutting part, to ensure highly efficient machining at a high revolving speed with large thrust force.

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Industrial Application The present invention relates to a drill for drilling holes in cast iron, steel, etc.

(B) Conventional technology and its problems High-speed steel drills have traditionally been used for drilling work in general steel materials, cast iron, etc. However, there has been a strong demand for improved efficiency in drilling work. Nowadays, there are an increasing number of cases in which the rotational speed of the drill is increased to meet the demands of G, and in such cases, a problem arises in the durability of drills made of high-speed steel. In other words, when the rotational speed of the drill is increased, the cutting speed at the outer periphery of the drill naturally becomes faster than that at the center, which causes severe wear and deterioration of the outer peripheral margin and outer cutting edge. Become. As a countermeasure, cemented carbide, which has excellent wear resistance, is sometimes used as drill material.
In the case of drill cutting, even if the squid G rotates at high speed, the cutting speed does not increase in the center (near the chisel blade), so normal cutting cannot be performed. Therefore, extremely strong strength is required in that part, otherwise the center There is an inherent problem that the cutting edge will break. On the other hand, cemented carbide, which has excellent wear resistance, has poor transverse rupture strength. Therefore, if this cemented carbide is used for the entire drill hole, the center cutting edge may break. is more obvious than looking at the fire.

This reduces the effective cross-sectional area of the main body.
In addition, the parts that are not involved in cutting must also have high strength, and each part of this type of drill, such as a general twist drill, requires different characteristics.

(c) The first means to solve the problem is to meet the above requirements and create a drill that matches the characteristics of the drill and is made of composite T-coated cemented carbide that is metallurgically integrated. It consists of one thing.

Specifically, the tip of the drill body made of tough cemented carbide is made small in diameter by at least a length corresponding to the regrinding amount O of the drill, or a part of the outer periphery of the tip is notched, and the outer periphery of this small diameter portion is reduced. Or the inside of the notch has more wear resistance than the above cemented carbide.
This excellent hard cemented carbide is integrally joined, and the center cutting part and non-cutting part of the drill tip are made of the strong cemented carbide of the main body (thus, the outer cutting part of the drill tip excluding the center cutting part is made of hard carbide). Forming hard public funds separately (Koyori,
This is done by matching the characteristics of each part of the drill to the required characteristics.

) Example An embodiment of the present invention is shown in FIGS. 1 and 2. FIG.

This drill 1 has a main body 2 made of cemented carbide Q, which has a toughness of 1. The tip of this main body has a length comparable to the amount of regrinding of the drill Thickness) is said to have a similar small diameter, and a chisel blade 3 is attached to the tip Q.Furthermore, a grinding tip 4 is also available to make the tip web thickness standard. Ru.

In addition, a hard cemented carbide 6, which is inferior in toughness but superior in wear resistance to the material of the main body, is integrally joined to the outer periphery of the small diameter portion 5 at the tip of the main body, and an outer peripheral cutting edge continuous to this cemented carbide center cutting edge. 7
This forms a margin portion 8 at the tip of the drill. Note that a margin portion 10 that is continuous with the non-cut portion 9 of the main body 2 is formed.

The hard cemented carbide 6 is joined to the main body by, for example, a third
As shown in Figures and Figure 4, the sintered body material 2a before being processed with grooves and blades, the outer periphery of the main body material 2a, and the annular cemented carbide raw powder molded body or its preliminary sintering. The body 6a is arranged coaxially with the small diameter part through a curved gap, and it is resintered to integrate it with the main body material, and then resintered as necessary, and the body is heated with high temperature and high pressure gas. (This method is a method for eliminating one cavity that occurs at the bonding interface.)
The metallurgical method disclosed in No. 7525 [
After this, the chip discharge groove 11, the cutting edge, and the outer peripheral margin portion may be formed by grinding and polishing.

Cemented carbide powder compact or preliminary sintered compact 6a
As shown in FIGS. 5 and 6, a point-symmetric notch 2b with respect to the rotation axis may be provided on the outer periphery of the tip of the main body material 2a, and the joint may be jointed there. The section is made of tough cemented carbide, while the peripheral cutting section at the tip is made of hard cemented carbide.

In addition to metallurgical methods, it is also possible to join the main body 2 and the hard cemented carbide 6 by brazing or press-fitting, but the former has a weak bonding strength and the melting temperature of the brazing material is low. Since the contact force of the chips and cutting heat are low, the joint boundary is likely to be destroyed. On the other hand, in the latter case, the hard cemented carbide 6 may break due to the tensile stress acting on the outer member during press-fitting. If there is, and the diameter of the small diameter part of the main body is larger than the drill core thickness, a chip discharge groove will be formed, and at this point, this alloy ring will be separated into two, so the pressing force against the main body will be lost. First, even if the small diameter portion is smaller than the core thickness, the groove is present in the circumferential direction (this is where the pressure contact force is unbalanced, and therefore both are unfavorable).

(E) Effects The drill of the present invention is explained below. As described above, the drill is made of tough cemented carbide in the non-cutting parts except for the center part where the cutting speed is slow and all or part of the outer periphery of the tip. Since the outer periphery of the fast-speed tip uses a cemented carbide that has better wear resistance than the cemented carbide mentioned above, the characteristics of each material are fully demonstrated, and therefore excessive thrust force (also not sufficient) is used. It withstands abrasion, has less damage to the center cutting edge, and less wear and deterioration of the outer cutting area, and enables high-efficiency machining by applying strong thrust force and high-speed rotation.

[Brief explanation of drawings]

FIG. 1 shows an example of the drill 11111-i of the present invention.
Fig. m and Fig. 2 are front views, Fig. 3 is a side view showing the state of the same drill before the flute alignment machining, and Fig. 4 is a 4.
Fig. 5 is a side view showing the state before groove and blade machining of another embodiment, Fig. 2 and 6 are cross-sectional views taken along line B-B of the same example. FIG. 1... Drill, 2... Main body, 2b... Notch, 3
... Chisel blade, 5. Small diameter part, 6. Hard cemented carbide, 796. Outer cutting edge, 8.10...Margin part, 9...
・Non-cutting part, 11...Chip discharge groove Patent applicant Sumitomo Electric Industries, Ltd. Agent
Sickle 1) Also two rings 1 Figure 2 Figure 3 Figure 4 Figure 5

Claims (1)

[Claims] The tip of the drill body made of tough cemented carbide is reduced in diameter by at least a length corresponding to the re-grinding length of the drill, or a part of the outer periphery of the tip is notched, and the outer periphery of this small diameter portion or the inside of the notch is reduced. A hard cemented carbide, which has better wear resistance than the cemented carbide mentioned above, is metallurgically integrated and joined, and the center cutting part and non-cutting part of the drill tip are connected to the strong cemented carbide of the main body. , On the other hand, a drill characterized in that the outer circumferential cutting portion of the tip of the drill excluding the central cutting portion is formed of the hard cemented carbide.