JPS6225292Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to a drill in which a cutting tip having a cutting edge is fixed to the tip of a drill body. Conventionally, as this type of drill, there is a cemented carbide drill whose cutting tip is made of cemented carbide. According to this carbide drill, it is possible to perform high-speed cutting compared to solid type drills made of high-speed steel.
It is possible to improve the efficiency of drilling work. However, it was not possible to improve the efficiency of the drilling operation by increasing the feed rate. This is because as the feed rate increases, the thrust load acting on the center of the cutting edge increases, which may cause the center of the cutting edge to collapse. In this regard, according to the drill that does not have a cutting edge at the center, that is, the drill in which the inner edge of the cutting edge is set 0.1 mm to 1.25 mm away from the rotation center axis of the drill body, which was proposed earlier by the applicant, the rotation center Since there is no cutting edge in the part, the thrust load can be significantly reduced and crushing of the cutting edge tip can be prevented.
Therefore, with such a carbide drill, not only can high-speed drilling be performed, but also high-feed drilling can be performed. However, when performing high-feed machining,
Welding on the cutting edge and the margin area, especially near the intersection of the cutting edge and the margin area, has become noticeable, resulting in worsening of the surface roughness of the drilled hole and shortening the life of the cutting edge tip. A problem has arisen. This idea was made in consideration of the above circumstances, and the purpose is to provide a drill that can significantly reduce welding on the cutting edge and margin, and that can perform even higher speed drilling. do. The feature of this design is that the part of the cutting edge where the inner periphery of the cutting edge is formed is made of cemented carbide, while the part where the outer periphery and the entire margin of the cutting edge are formed is made of cermet. Or the diameter d according to the rotation locus of the cutting edge part made of ceramics or ultra-high pressure material and made of cemented carbide, and the diameter d of the cutting edge part made of cermet, ceramics or ultra-high pressure material. The point is that the relationship with the diameter D according to the rotation locus is 0.5D≦d≦0.8D. This is because if d is set to 0.8D or more, a problem will occur in the bonding strength, while if d is set to less than 0.5D, the cutting speed on the inner circumference side and the cutting speed on the outer circumference side of the part made of cermet etc. This is because there is a risk that a large difference will occur and the life of that part will be shortened. The ultra-high pressure material referred to here is cubic boron nitride.
etc. An embodiment of this invention will be described below with reference to FIG. In addition, FIG. 1 shows a drill according to this invention, and A is a bottom view thereof, and B is a partially omitted side view thereof. In FIG. 1, reference numeral 1 indicates a drill body made of steel. Chip discharge grooves 2, 2 extending from the tip toward the rear end are formed on the outer circumference of the drill body 1. At the tip of the wall facing the rotation direction of each chip discharge groove 2, there are two cutting chips 3 and 4.
are radially adjacent and fixed by brazing. The cutting edge tip 3 on the inner circumferential side is made of cemented carbide, and the cutting edge tip 4 on the outer circumferential side is made of cermet, ceramics, or ultra-high pressure material. A cutting edge 5 is formed at the tip of each of the cutting tips 3 and 4, and extends from the inner edge of the cutting edge 3 to the outer edge of the cutting edge 4. Therefore, the inner peripheral portion of the cutting blade 5 is made of cemented carbide, and the outer peripheral portion thereof is made of cermet, ceramic, or ultra-high pressure material. In this case, the diameter according to the rotation locus of the cutting edge 5 portion constituted by the cutting edge tip 3, that is, the diameter of the two cutting edge tips 3, 3
As mentioned above, when the external dimension of the cutting edge is d, and the external dimension of the cutting blade tips 4, 4 is D, as mentioned above,
It is set to 0.5D≦d≦0.8D. Note that the two cutting blades 5, 5 are formed point-symmetrically with respect to the rotational center axis O, and the inner edge 5a thereof is provided at a distance of 0.1 mm to 1.25 mm from the rotation center axis O.
In addition, on the outer periphery of the cutting blade tip 4, the tip is a cutting blade 5.
A margin portion 6 is formed that intersects with. However, when drilling, particularly high-feed drilling, is performed using a drill configured in this manner, the cutting edge 5 and the margin portion 6 have a welding resistance that is lower than that of cemented carbide. A cermet that is extremely superior to
Since it is made of ceramics or ultra-high pressure material, welding of those parts can be greatly reduced. In this case, if the feed speed is normal, welding of the margin portion 6 can be prevented due to the back taper provided to the margin portion 6.
It is sufficient to construct only the tip portion with cermet or the like. However, in a drill like this invention, in which the inner edge 5a of the cutting edge 5 is separated from the rotation center axis O, the feed rate can be two to three times that of a normal drill, and it is possible to drill such high-feed holes. During machining, the hole that once expanded due to cutting heat contracts. For this reason,
If the margin part 6 is provided with a back taper of a size that does not impair the guiding action, the entire margin part 6 will come into contact with the wall surface of the hole, and therefore it will not be possible to sufficiently prevent welding to the margin part 6. It ends up. In this regard, in the above drill, since the entire margin portion 6 is made of cermet or the like, the margin portion 6 can be reliably welded. As a result, the surface roughness of the hole and the life of the cutting edge 5 can be significantly improved. Furthermore, since cermets, ceramics, and ultra-high pressure materials are all harder than cemented carbide, the rotational speed of the drill can be increased to perform even higher-speed drilling. In addition, the diameter d according to the rotation locus of the inner cutting edge tip 3 (the cutting edge part made of cemented carbide) and the outer cutting edge tip 4 (made of cermet, ceramics, or ultra-high pressure material) Since the relationship with the diameter D according to the rotation locus of the cutting edge portion (constituting the cutting edge portion) is 0.5D≦d≦0.8D, the bonding strength of the cutting edge tip 4 on the outer circumferential side is sufficient, and the It can prevent chipping of the cutting edge part and improve the lifespan. In order to demonstrate the critical significance of such numerical limitations and the effects of such numerical limitations, test results are shown below. [Test results] Drill configuration Material of inner cutting edge tip 3 Cemented carbide Material of outer cutting edge tip 4 Cermet Diameter of outer cutting edge tip 4 D 20 mm Cutting conditions Number of revolutions 954 rpm Feed 0.3 mm/ rev Work material Material S48C Hardness HB200 Depth 20mm Number of holes drilled 10 50 drills each of 5 types (4 mm, 7 mm, 10 mm, 13 mm, 16 mm, 19 mm) with diameter d for the cemented carbide part were manufactured. , compared under the conditions described above. The results are shown in Table 1, including the bonding strength and life of the cutting blade 4 on the outer peripheral side.

[Table] As is clear from the above test results, the diameter d according to the rotation locus of the inner cutting edge tip 3,
It can be seen that chipping is likely to occur when the relationship between the rotation locus of the cutting edge tip 4 on the outer peripheral side and the diameter D is 0.5D (=20mm)>d. This is because when the length of the cutting edge of the cutting edge tip 4 on the outer circumferential side is long, there is a difference in cutting speed (peripheral speed) between the inner part and the outer part. However, the cutting speed is slower on the inner circumference than on the outer circumference). In other words, if a material with extremely high hardness such as cermet is used for the outer cutting edge part and 0.5D>d, the inner part where the cutting speed (circumferential speed) is slow is likely to chip. This shortens the life of the drill. This also applies to ceramics and cubic boron nitride. Furthermore, if the relationship between the diameter d according to the rotation locus of the inner cutting edge tip 3 and the diameter D according to the rotation trajectory of the outer cutting edge tip 4 is d>0.8D (=16 mm), the cutting It can be understood that the joint area of the cutting blade tip 4 and the drill body 1 due to brazing becomes smaller, and the frequency of peeling and falling off of the cutting blade tip 4 increases. That is, the dimensional relationship between the diameter d of the cutting blade portion 3 made of cemented carbide according to the rotational trajectory and the diameter D of the cutting blade portion 4 made of cermet according to the rotational trajectory is 0.5D≦d. When ≦0.8D, it is possible to satisfy the contradictory requirements of bonding strength and life. Moreover, FIG. 2 shows another embodiment of this invention. In this embodiment, the cutting blade tip 7 is made of cemented carbide.
A step part 8 extending from the tip to the rear end is formed on the outer periphery of the blade, and a cutting edge tip 9 made of cermet, ceramics, or ultra-high pressure material is fixed to this step part 8 by brazing. Cutting blade 5 on 9
The outer peripheral part of the margin part 6 is formed, and the margin part 6 is formed.
is formed. Note that the other configurations are similar to those of the above embodiment, and similar parts are denoted by the same reference numerals and explanation thereof will be omitted. In this case,
The cutting edge tip 7 and the cutting edge tip 9 may be integrated in advance and then brazed to the drill body 1, or the cutting edge tip 7 and the cutting edge tip 9 may be brazed one after another. good. In the above embodiment, two cutting edges 5 are formed, but one or three or more cutting edges 5 may be formed. As explained above, according to the drill of this invention, the part of the cutting edge tip where the inner circumference of the cutting edge is formed is made of cemented carbide, while the outer circumference and the entire margin of the cutting edge are made of cemented carbide. Since the part is made of cermet, ceramics, or ultra-high pressure material, welding at the cutting edge and margin part can be significantly reduced, and furthermore, high-speed drilling can be performed. can get. In addition, the dimensional relationship between the diameter d according to the rotation locus of the cutting blade made of cemented carbide and the diameter D according to the rotation locus of the cutting blade made of cermet, ceramics, or ultra-high pressure material is 0.5. D
Since ≦d≦0.8D, the bonding strength of the cutting edge portion made of cermet or the like can be made sufficient, and furthermore, the cutting edge portion can be prevented from chipping and the service life can be extended.

[Brief explanation of the drawing]

FIG. 1 shows an embodiment of this invention, A is a bottom view thereof, B is a partially omitted side view thereof, and FIG. 2 is another embodiment of this invention, A is a bottom view thereof,
B is a partially omitted side view. 1... Drill body, 3, 4... Cutting tip, 5
... Cutting edge, 5a ... Inner edge, 6 ... Margin part,
7, 9... Cutting blade tip, O... Rotation center axis.

Claims (1)

[Scope of utility model registration request] A cutting tip is fixed to the tip of the drill body by brazing, and the inner edge of the tip of the cutting tip is 0.1 mm to 1.25 mm from the rotation center axis of the drill body.
In the drill, in which cutting edges are formed separately from each other and a margin is formed on the outer periphery of the cutting edge, the portion of the cutting edge where the inner periphery of the cutting edge is formed is made of cemented carbide. The rotation locus of the cutting blade portion is configured such that the outer circumferential portion and the entire margin portion of the cutting blade are made of cermet, ceramics, or ultra-high pressure material, and the portion is made of cemented carbide. and the diameter D due to the rotation locus of the cutting edge portion made of cermet, ceramics, or ultra-high pressure material.
A drill characterized in that the relationship between the two is 0,5D≦d≦0,8D.