JPS6225293Y2 - - Google Patents

Description

[Detailed explanation of the idea]

This invention relates to a carbide drill in which a cutting tip made of cemented carbide and having a cutting edge is fixed to the tip of a drill body. In general, since the cutting edge of a cemented carbide drill is made of cemented carbide, the advantage is that the cutting speed can be increased. but,
As for the feed speed, it is not possible to make it that fast. Theoretically, the relief angle of the cutting edge should be set at nearly 90° at the center of the drill, but in reality, the cutting edge has to be set at about 10° for strength reasons, and as a result, the drill This is because a large thrust load acts on the center portion and its vicinity, and if a high feed rate is attempted, there is a risk that the center portion of the cutting edge may be crushed by the large thrust load. In this regard, according to a carbide drill without a cutting edge in the center, that is, a carbide 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, which the present applicant proposed earlier, the rotation Since there is no cutting edge in the center, the thrust load can be significantly reduced.
Therefore, high-feed drilling can be performed. However, when performing high-feed drilling, the cutting load acting on the cutting edge increases accordingly.
As a result, another problem has emerged in that the surface roughness and roundness of the hole deteriorate. Furthermore, when high-feed drilling is performed, the degree of welding at the cutting edge and margin increases, further exacerbating the above-mentioned problems. This invention was made in consideration of the above circumstances, and aims to provide a carbide drill that can improve the surface roughness and roundness of the hole. This idea will be explained in detail below. First, to describe the features of this device, this device fixes a finishing tip made of cermet, ceramics, or ultra-high pressure material to the outer periphery of the tip of the drill body behind the cutting edge. The dimensional relationship between the diameter D according to the rotation trajectory and the diameter d according to the rotation trajectory of the cutting blade is d<D, and the difference in these diameters is 0.01×d≦(D-d)≦0.1
The feature is that it is marked as ×d. This is the diameter difference (D-
If d) is smaller than 0.01 x d, there is a risk that the finishing allowance will be insufficient and it will be impossible to improve surface roughness and roundness.On the other hand, if it is larger than 0.1 x d, the cutting load acting on the finishing blade will be This is because the finishing blade becomes too large to perform its function as a finishing blade, and as a result, improvement in surface roughness and roundness cannot be expected. The ultra-high pressure material referred to here is, for example, cubic boron nitride (Cubic Boron nitride).
Nitride) etc. Next, in order to clarify the above-mentioned characteristics more clearly, the attached first example of this invention will be explained.
This will be explained with reference to the figures and FIG. In addition, the first
The figure is a bottom view of the carbide drill according to this invention.
The figure is a partially omitted side view. In these figures, reference numeral 1 indicates a steel drill body. Chip discharge grooves 2, 2 are formed on the outer periphery of the drill body 1, extending from the tip toward the rear end. Cutting blade tips 3, 3 made of cemented carbide are fixed to the tip portions of the wall surfaces of these chip evacuation grooves 2, 2 facing the direction of rotation, respectively. In this case, the cutting blade tips 3, 3 are fixed by brazing, but it goes without saying that they may be fixed by tightening bolts or the like. Furthermore, cutting edges 4, 4 are formed at the tip of each cutting edge tip 3, 3. These cutting blades 4, 4 are arranged point symmetrically with respect to the rotation center axis O, and each inner edge 4a, 4a of the cutting blades 4, 4 is
are all 0.1 mm or more from the rotation center axis O.
1.25mm apart. The above configuration is the same as that of a conventional carbide drill. However, in this carbide drill, finishing blade tips 5, 5 are fixed by brazing to the rear of the cutting blade tips 3, 3 on the outer periphery of the wall surface facing the rotation direction of each chip discharge groove 2, 2. There is. This finishing blade tip 5 is made of cermet, ceramics, or ultra-high pressure material, and a finishing blade 6 is attached to its tip.
is formed. Of course, the diameter D according to the rotational trajectory of the finishing blade 6 is larger than the diameter d according to the rotational trajectory of the cutting blade 4 by the finishing allowance, but the difference in these diameters (D-d) is 0.01 The relationship is ×d≦(D−d)≦0, 1×d. However, when drilling is performed using a carbide drill configured as described above, the cutting edge 4,
Finishing blades 6, 6 will finish the hole drilled by 4. In this case, finishing blades 6, 6
Since it cuts only a very small amount, the cutting load acting on it is extremely small compared to the cutting load acting on the cutting edges 4, 4. Therefore, even if high-feed drilling is performed, the cutting edges 4, 4
Even if the surface roughness and roundness of the hole drilled by this method deteriorate, the surface roughness and roundness of the hole finally obtained can be significantly improved. Moreover, the cermets, ceramics, and ultra-high pressure materials used for the finishing blade tip 5 are
Since the welding resistance is much superior to that of cemented carbide, welding of the finishing blade tip 5 to the finishing blade 6 and the margin part 7 is reduced, which improves the surface roughness and roundness of the hole. This can be further improved. Moreover, as a result of improving surface roughness and roundness, post-process reaming and the like can be omitted. Furthermore, since cermet and the like have higher hardness than cemented carbide, the cutting speed can be further improved. In addition, the diameter D according to the rotation locus of the finishing blade tip 5
The diameter difference (D-d) between the diameter and the diameter d due to the rotation locus of the cutting blade is 0,01×d≦(D-d)≦0,1×
The effect of setting d, especially its critical significance, will be clarified through the following comparative example. [Comparative example] Sample A Material of the cutting edge tip of the proposed invention Material of the cemented carbide finishing tip Diameter d of the cermet cutting edge 20 mm Sample B Same cutting conditions and rotation as sample A except that the finishing tip is not formed Number: 955rpm Feed: 0.3mm/rev Work material: S45C Hardness: HB200 Depth: 40mm Comparison conditions Test 1 For sample A, the diameter D according to the rotational trajectory of the finishing blade tip 5 and the diameter d according to the rotational trajectory of the cutting edge are The diameter difference (D-d) is
0.1mm・0.2mm・1.0mm・respectively
For each case of 2.0 mm and 3.0 mm, 50 holes were drilled, the roundness and surface roughness were measured, and the average values were taken. Test 2 For Sample B, 50 holes were drilled, the roundness and surface roughness were measured, and the average value of each was taken. Test 3 Sample B was further subjected to semi-finishing using a core drill after Test 2, and then the roundness and surface roughness were measured, respectively.
The average value was taken. Also, the machining allowance is 1.0 mm.
(diameter). ...About roundness...

【table】 ...About surface roughness...

[Table] As is clear from this comparative example, 0.01
× When d≦(D-d)≦0,1d, that is, in the case of 0,2≦(D-d)≦2,0 in the above test example, when performing semi-finishing using a core drill, It can be seen that comparable roundness and surface roughness can be achieved. In addition, in the above embodiment, the finishing blade tip 6
is fixed to the wall surface of the chip discharge groove 2, but the present invention is not limited to this. The positions of the blade and the finishing blade in the rotational direction may be largely shifted. In this case, the number of restraining points in the circumferential direction of the drill is 4 points instead of 2, and the roundness can be further improved.
However, in this case, it is necessary to form a new chip discharge groove for the finishing blade. In addition, in the above embodiment, both the cutting blade 4 and the finishing blade 6 are
Although two are formed, only one may be formed. Furthermore, the finishing blade tip 5 may be fixed with a tightening bolt. As explained above, according to the carbide drill of this invention, a finishing tip made of cermet, ceramics, or ultra-high pressure material is fixed to the outer periphery of the tip of the drill body behind the cutting edge. The diameter difference between the diameter D according to the rotational trajectory of the tip and the diameter d according to the rotational trajectory of the cutting blade is 0.01×d≦(D−
d) Since ≦0, 1×d, it is possible to improve the surface roughness and roundness of the hole, and as a result, it is possible to omit the finishing process using a core drill, etc., and even higher speeds can be achieved. Effects such as being able to perform cutting can be obtained.

[Brief explanation of drawings]

The attached drawings show an embodiment of this invention, with FIG. 1 being a bottom view thereof and FIG. 2 being a partially omitted side view thereof. 1... Drill body, 3... Cutting tip, 4...
Cutting blade, 4a... Inner edge, 5... Finishing blade tip, 6
...Finishing blade, O...Rotation center axis.

Claims (1)

[Scope of utility model registration request] A cutting blade tip made of cemented carbide is fixed to the tip of the drill body, and the inner edge of the cutting tip is 0.1 mm to 1.25 mm from the rotation center axis of the drill body.
In a carbide drill with separated cutting edges,
A finishing blade tip made of cermet, ceramics, or ultra-high pressure material is fixed to the outer periphery of the tip of the drill body behind the cutting blade, and the diameter D according to the rotation trajectory of the finishing blade tip and the rotation trajectory of the cutting blade are fixed. Let the dimensional relationship with the diameter d be d<D and the difference in these diameters be 0.
A carbide drill characterized by having a diameter of 0.1×d.