JPH0318090Y2 - - Google Patents

Description

[Detailed Description of the Invention] This invention relates to a cemented 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 this fast. This is because the relief angle of the cutting edge should theoretically be set at nearly 90° at the center of the drill, but in reality it has to be set at around 10° due to the strength of the cutting edge.
As a result, a large thrust load acts on the center of the drill and its vicinity, and if a high feed rate is attempted, there is a risk that the center of the cutting edge will be crushed by the large thrust load.

In this regard, according to a carbide drill without a cutting edge in the center, which was previously proposed by the present applicant, that is, a carbide drill in which the inner edges of the two cutting edges are placed 0.1 mm to 1.25 mm away from the rotation center axis. Since there is no cutting edge at the center of rotation, the thrust load can be significantly reduced and high-feed drilling can be performed.

However, when high-feed drilling is performed, the result is similar to so-called rough drilling, and another problem has emerged in that the surface roughness of the hole deteriorates.

This invention was made in consideration of the above-mentioned circumstances, and aims to provide a carbide drill that can improve the surface roughness of the hole.

This idea will be explained in detail below.

First, to describe the features of this device, this device has multiple pads on the outer periphery of the tip of the drill body, and these pads burnish the wall surface of the hole and guide the drill itself. Its characteristics lie in the points. In this case, the shape of the pad is arbitrary, but the diameter of the circle formed when the pad rotates as the drill rotates is larger than the diameter of the cutting edge (outer diameter of the drill) by the burnishing allowance. Make it bigger. It is desirable that this burnishing allowance be made as small as possible within a range that can crush the feed marks of the drill, etc. This is to minimize the increase in torque due to the pad. Furthermore, although cemented carbide is usually used as the material for the pad, cermet or ceramic may also be used to prevent welding.

Next, regarding one embodiment of this invention, Fig. 1A,
This will be explained with reference to B. In addition, FIG. 1A is an axial tip end view of the carbide drill according to this invention, and FIG. 1B is a partially omitted side view thereof. In the figure, reference numeral 1 indicates a steel drill body. At the tip of the drill body 1, there is a cutting tip 2 made of cemented carbide.
2 is fixed. In this case, the cutting blade tip 2,
2 is fixed by brazing, but may be detachably fixed using a tightening bolt or the like. Furthermore, cutting edges 3, 3 are formed at the tips of these cutting edges 2, 2. These cutting blades 3, 3 are arranged point symmetrically with respect to the rotation center axis O, and the cutting blades 3,
Each of the inner edges 3a, 3a of No. 3 is spaced apart from the rotation center axis O by 0.1 mm to 1.25 mm. The above configuration is the same as that of a conventional carbide drill.

However, in this carbide drill, the cutting edges 2, 2 on the outer periphery of the tip of the drill body 1 are attached to the heel portions 4, 4, which are the portions other than the fixed portion, extending in the direction of the rotation center axis O. Two plate-shaped pads 5, 5 are each fixed. This patch 5
The method is to improve the surface roughness of the wall surface of the hole by burnishing the feed marks and the like. Therefore, it goes without saying that the diameter of the pad 5 based on the rotational trajectory needs to be larger than the diameter of the cutting blade 3 based on the rotational trajectory, but it is desirable to make it as small as possible within the range that can close the eye. Also, while Patsudo 5 closes his eyes,
It guides the drill itself. Therefore, it is desirable that the pads 5, 5 be arranged point-symmetrically with respect to the rotation center axis O, as shown in FIG. 1A. Note that the pad 5 may be fixed by brazing or may be detachably fixed using a tightening bolt.

When a hole is drilled using a carbide drill constructed in this manner, the pad 5 burnishes the wall surface of the hole, thereby improving the surface roughness. In addition, in the carbide drill of this invention, by providing a pad in the center of the drill without a cutting edge, it is possible to improve not only the surface roughness but also the roundness and cylindricity of the hole. This effect can also be obtained.

That is, in a drill without a cutting edge in the center, the thrust load can be significantly reduced, so the straightness of the drill is good, and therefore the cylindricity of the hole can be improved. However, even with drills that do not have a cutting edge in the center, when the feed rate is increased, the imbalance in the cutting load acting on the two cutting edges becomes noticeable, resulting in a so-called polygonal error in which the cross-sectional shape of the hole forms a polygon. occurs, and the roundness deteriorates. On the other hand, if a pad is provided on a regular drill with a cutting edge in the center, the polygonal error can be corrected by the burnishing action of the pad, thus improving the roundness of the hole. I can do it.
However, in a drill with a cutting edge in the center, the thrust load is large and the drill is therefore prone to buckling deformation. Moreover, it is inevitable that the cutting loads acting on the two cutting edges become unbalanced. These 2
Holes often become bent due to two factors. The bending of this hole increases as the feed rate increases. And once the hole is bent, little correction of cylindricity can be made since the pad simply guides the drill along the hole, so in drills with a central cutting edge, the pad only guides the drill along the hole. Even if a hole is provided, it is difficult to improve the cylindricity of the hole.

In this regard, in the drill of this invention, since the pad is provided on a drill without a cutting edge in the center, it has the advantage of reducing the thrust load that a drill without a cutting edge in the center has, compared to a normal drill with a cutting edge in the center. The problem of deterioration in cylindricity of drills provided with pads can be solved, and on the other hand, the advantage of drills provided with pads can solve the problem of deterioration of roundness, which is caused by drills without a cutting edge in the center. That is, according to the drill of this invention, cylindricity and roundness can be significantly improved. moreover,
Since the drill is restrained by pad 5,
It is possible to drill holes with a constant diameter and high precision.

Moreover, by providing the pads 5, 5, it is also possible to prevent the inner edge 3a of the cutting blade 3 from being damaged. In other words, increasing the feed rate increases the cutting force,
Therefore, it is inevitable that the drill vibrates. When the drill vibrates, the inner edges 3a, 3a repeatedly contact (impact contact) and separate from the core formed between them, and as a result, the inner edges 3a may be damaged. In this regard, in the above drill, since the drill itself is restrained by these two pads 5, 5, it is possible to prevent the drill from vibrating. Therefore, the inner edge 3a can be kept in contact with the core at all times, and damage to the inner edge 3a can be prevented.

Next, other embodiments of this invention shown in FIGS. 2 to 4 will be described. Note that the same parts as in the above embodiment are denoted by the same reference numerals, and the explanation thereof will be omitted. Moreover, it goes without saying that the same effects as in the above-mentioned embodiments can be obtained in the embodiments described below.

The carbide drill shown in FIG. 2 has, in addition to the pads 5, 5 described above, other pads 6, 6 adjacent to the rear of the cutting tips 2, 2 fixed by brazing.

In addition, the carbide drill shown in Fig. 3 has pads 7,
7 is formed into a cylindrical shape, and its axis is the rotation center axis O.
It is rotatably provided on the outer periphery of the drill body 1 so as to be parallel to the drill body 1. In this case, since the pads 7, 7 are rotatable, the torque generated by burnishing can be reduced.

Furthermore, the carbide drill shown in FIG. 4 has spherical pads 8, 8 rotatably provided on the outer periphery of the drill body 1. In this case as well, it is possible to reduce the torque due to burnishing.

As explained below, according to the carbide drill of this invention, each part of the outer periphery of the tip of the drill body other than the part where the cutting blade tip is fixed has a diameter according to the rotational trajectory of the cutting blade. Since a larger pad is provided, it is possible to improve the surface roughness, roundness and cylindricity of the hole, and it is also possible to drill holes with a constant diameter with high accuracy, and it is possible to prevent defects on the inner edge. Effects such as being able to prevent this can be obtained.

[Brief explanation of drawings]

The attached FIGS. 1 to 4 each show an embodiment of this invention, in which A is a front end view in the axial direction, and B is a partially omitted side view. 1... Drill body, 2... Cutting tip, 3...
Cutting blade, 3a...inner edge, 5, 6, 7, 8...pad, 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 is 0.1 mm to 1.25 mm from the rotation center axis of the drill body.
In a carbide drill formed of two cutting blades that are spaced apart by mm and located approximately point symmetrically, a rotation trajectory is formed on each part of the outer periphery of the tip of the drill body other than the part where the cutting blade tip is fixed. 1. A carbide drill, characterized in that the pad is provided with a pad whose diameter is larger than the diameter according to the rotation locus of the cutting blade.