JPS6147645B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to improvements in drills, primarily solid type drills.

Various types of drills are known, such as solid types, blade types, and throw-away types, but the problem here is that the cutting edge and shank are made of one material such as steel. The generally constructed solid type, and for example the shank, is a so-called super-hardened solid type in which the cutting edge is made of steel and the cutting edge is made of cemented carbide. In the following, a general solid type will be described, but it should be made clear here that the present invention is also applicable to super-hardened solid types.

For general solid type drills,
As shown in Figures 1 and 2, there is a chisel edge 1 and cutting edges 2 and 3 at the center of rotation _OR , and therefore the thrust load is large due to insufficient relief angle at the center of rotation _OR . Various damages such as easy damage to the cutting blades 2 and 3 due to peeling of the weld at the center of rotation _OR are unavoidable. Regarding this point, for example, see "Cutting and Grinding Processing, Volume 1" on page 332.
~334, written by Eiji Usui and published by Kyoritsu Shuppan.

Therefore, in order to solve the above-mentioned problems, the present applicant moved the inner edge of the cutting edge away from the center of rotation of the tool body relative to the workpiece, that is, eliminated the cutting edge from the center. On the other hand, on the other hand, the area in the center where there is no cutting edge is reduced to a certain size or less (the distance from the center of rotation to the inner edge of the cutting edge is d/2).
We previously proposed a drilling tool that can drill holes without leaving a core even without a cutting edge in the center by setting the value 0.1mm≦d/2≦1.25mm (patent application). (See No. 127046, 1983).

The present invention applies the idea in the previous proposal to a solid type drill, and provides a drill that is particularly easy to manufacture.

Hereinafter, the content of the present invention will be explained in detail with reference to the embodiments shown in the accompanying drawings (FIGS. 3 to 6).

3 and 4 show an embodiment of the present invention, in which the drill has a cylindrical shape extending from the tip F of the cutting edge where the cutting edges 12 and 13 are located toward the shank side. Round hole 4 is chisel edge 1
It is provided to divide 1. This round hole 4
is along the axis of the drill body including the blade part and the shank part, but the radial distance (d/2) from its center (rotation center O _R ) to the wall surface produces a cylindrical core as described above. On the other hand, the depth (l) is set to a value that allows re-grinding to be performed an appropriate number of times.

In order to form such a round hole 4, when the blade part is made of cemented carbide, it can be formed after preliminary sintering (of course, it can also be formed beforehand when stamping the powder), or If the drill is made of high-speed steel, drilling it before quenching will improve workability, while for conventional drills that have already been completed, this can be done by electrolytic machining or electrical discharge machining.

In any case, by providing the round hole 4 in this way, the actual length of the chisel edge 11, which has a large negative rake angle (generally around -60°), is shortened, for example, compared to the conventional one. This will reduce the thrust load from that part significantly. Furthermore, what is fundamentally different from the conventional method is that there is no cutting edge in the center.
Unlike conventional thinning, which cuts both ends of the chisel edge and simply shortens the actual length of the chisel edge while leaving the cutting edge in the center, the thrust load generated is It can be made very small. This is because when drilling a hole with a drill, the closer to the center of rotation _{O The R} section requires a clearance angle of nearly 90°, but in practice it is impossible to provide such a clearance (especially when made of cemented carbide, the clearance angle is limited to around 10°). ,
Therefore, in a drill with a cutting edge in the center, the pressing force corresponding to the feed caused by contact with the flank of that part accounts for a large proportion of the total thrust load. However, in this invention, by providing the round hole 4 in the center, this problem of insufficient clearance angle is completely solved. As mentioned above,
According to this invention, the thrust load at the center including the chisel edge is greatly reduced. In particular, the thrust load at the chisel portion accounts for 30 to 50% of the total thrust load, so the reduction effect is very large. In addition, since the cutting edge has been removed from the center of rotation _OR , there is no zero cutting speed region, which prevents welding and peeling even when cutting materials with heavy welding, such as steel, which was previously considered to be extremely disadvantageous when using cemented carbide. This is advantageous when using cemented carbide. Moreover, since the distance d/2 from the center of the round hole 4 (rotation center O _R ) to the wall surface is set to 0.1 mm≦d/2≦1.25 mm, it should grow relatively within the round hole 4. Of course, the core can be threaded by the frictional force acting between it and the wall of the round hole 4.
Furthermore, in this embodiment, the remaining chisel portions at both ends bite into the workpiece while leaving a slight cylindrical core on the workpiece side, and this core acts to suppress the lateral vibration of the tip of the drill. It is difficult to cause "miso grinding motion" and has excellent grip stability on the work material. Therefore, a highly accurate hole can be obtained without inducing chatter vibration in the drill, and the cutting edge is less likely to be damaged.

Next, FIGS. 5 and 6 show another embodiment of the present invention, in which the tip portion F of the drill body (or blade portion) is thinned 5 to completely remove the chisel edge 11. Further, a round hole 40 corresponding to the cylindrical round hole 4 is penetrated to the base side of the drill body. Of course, in this case, it is also possible to perform thinning 5 or only the round hole 40, but if thinning 5 is performed, the problem caused by the presence of the chisel edge can be more completely eliminated, and the If the round hole 40 is formed as described above, a constant cross section can be obtained even after many re-grinding operations, and an additional effect can be obtained in that the round hole 40 can be used as an oil hole for supplying cutting oil. Therefore, in this example where both are implemented, not only can the problem caused by the presence of a chisel edge be solved, but the amount of regrinding that can be done is larger and it is more economical.
Moreover, a drill with good cooling and lubrication of the cutting edge and good chip evacuation can be obtained, making it possible to perform cutting at higher speeds and feeds, thereby improving machining accuracy and extending the life of the drill.

In each of the above embodiments, the elongated holes provided in the tool body are circular holes 4, 40, that is, the cross-sectional shape is circular, but the elongated holes may have other cross-sectional shapes such as an ellipse or a rectangular cross-section. It is also possible to do this. However, even in that case, it is important to set the maximum diameter of the elongated hole within a range that does not generate the above-mentioned core, and to make the cross-sectional shape in the axial direction uniform to enable re-grinding. However, if the cross-sectional shape of the elongated hole is circular, it can be formed more easily, the mechanical strength of the drill itself can be made more stable, and the elongated hole (round hole) can be centered. Since it can also be used as a hole, it is extremely advantageous for drilling.

[Brief explanation of the drawing]

Fig. 1 is a front view showing a conventional drill, Fig. 2 is a bottom view thereof, Fig. 3 is a front view showing an embodiment of the present invention, Fig. 4 is a bottom view thereof, and Fig. 5 is a bottom view of the drill. FIG. 6 is a front view showing another embodiment, and FIG. 6 is a bottom view thereof. 2, 3, 12, 13... Cutting blade, 4, 40... Round hole (long hole), O _R ... Center of rotation.

Claims (1)

[Scope of Claims] 1. The drill body is provided with an elongated hole extending in the axial direction from the tip end with the cutting blade toward the shank side, and the elongated hole is aligned with the center of the axis of the drill body. and a radial distance d/2 from the center to the wall of the elongated hole is set to 0.1 mm≦d/2≦1.25 mm. 2. The drill according to claim 1, wherein the elongated hole has a uniform cross-sectional shape in the axial direction. 3. The drill according to claim 2, wherein the drill has a circular cross-sectional shape.