JPH0647612Y2 - Drill - Google Patents

Description

[Detailed Description of the Invention] [Industrial application] The present invention relates to a drill, and more specifically, in a drill in which the tip of the drill is thinned to form a narrow chisel edge, the cutting edge at the tip of the drill is used. The present invention relates to a drill which has a straight cutting edge and an arc-shaped cutting edge so that cutting scraps can be favorably discharged to the outside and the cutting efficiency is improved.

[Background of the Invention] A drill is often used as a cutting tool for drilling a workpiece. Various forces act on the drill during cutting, and among them, the cutting resistance that acts on the chisel edge portion formed at the tip of the drill is the largest. Therefore, various types of so-called thinned drills are used in which a cutting groove is formed at the tip of the drill to narrow the width of the chisel edge portion to reduce the cutting resistance applied to this portion.

Therefore, FIG. 1 shows a general configuration of a drill of this type, taking a three-blade drill as an example. That is, this drill 2 has 3
A sheet of cutting edge 4 and a corresponding twist groove 6 are formed.
Then, the tip portion thereof is thinned, and a cut groove 9 is formed to narrow the chisel edge portion 8.

With regard to a drill having three or more blades of this type, the applicant of the present application has already disclosed in Japanese Patent Application No. 61-134927 that a chisel edge portion is sharply defined to further narrow the chisel edge portion. We are proposing a drill with further improved cutting efficiency.

By the way, chips are naturally generated during cutting. For example, when cutting a copper material having low brittleness, long chips are generated. Generally, the width of the twist groove is narrower in a drill with three or more blades than in a drill with two blades. Particularly, in the drill 2 as shown in FIG. 1, since the cutting edge 4 at the tip has a linear shape, chips are difficult to be divided and it is difficult to quickly discharge the chips to the outside through the twist groove 6. As a result, it is feared that the cutting efficiency will decrease.

[Object of the Invention] The present invention has been made in connection with the above application,
In a drill with a sharp cutting groove formed at the tip of the drill and thinning to make the chisel edge narrow, the cutting edge at the tip of the drill is a straight cutting edge starting near the center of rotation of the chisel edge. And an arc-shaped cutting edge that is continuous with this straight cutting edge, reduces the cutting resistance that the chisel edge receives during cutting, improves chip discharge, and demonstrates high-efficiency cutting performance. The purpose of the present invention is to provide a drill that makes it possible.

[Means for Achieving the Purpose] In order to achieve the above object, the present invention provides a drill having three cutting blades, the body having a thinned tip and a shank portion. The first edge of the cutting edge is deviated by a predetermined distance t from the rotation center O of the drill to the front side in the rotation direction, and divides the tip into three equal parts
It is orthogonal to the second reference line S ₁ which is inclined forward by a predetermined angle θ with respect to the reference line S, and is located at a position beyond a virtual straight line passing through the rotation center O, and extends linearly from the cutting edge tip. A straight cutting edge having a negative rake angle in the radial direction whose end point is the intersection with the end edge of the twist groove formed in the body, and a radial direction continuous from the intersection point along the end edge. The rake angle is formed by a negative arcuate cutting edge.

[Embodiment] Next, preferred embodiments of the drill according to the present invention will be given and described in detail below with reference to the accompanying drawings.

In FIG. 2, reference numeral 10 indicates a drill according to the present invention, and the drill 10 basically comprises a body 12 and a shank portion 14 connected to the body 12.

Three twist grooves 16a to 16c are formed in the body 12 so as to screw the body 12, and correspondingly, first flanks 18a to 18c and second flanks 20a to 20c are formed. It is formed. Twisted grooves 16a to 1 of the first flanks 18a to 18c
Cutting edges 22a to 22c are formed on the edge portion on the 6c side.

On the other hand, a flat portion 23 is formed on the shank portion 14 so that it can be easily gripped by a chuck holder or the like.

As shown in FIG. 3, the first flanks 18c to 18c, the second flanks
The flanks 20a to 20c and the cutting edges 22a to 22c extend to the tip portion 24 of the body 12 and converge at a chisel edge portion 26 formed at the central portion of the tip portion 24. The tip portion 24 is thinned to form cut grooves 28a to 28c. In this case, the cutting grooves 28a to 28c are formed so that the sharp tips of the cutting grooves 28a to 28c are oriented so as to be slightly deflected with respect to the rotation center O of the chisel edge portion 26 and cut as sharply as possible. As a result, the chisel edge portion 26 is narrowly formed.

Further, the cutting edges 22a to 22c are formed at the tip portion 24 by straight cutting edges 30a to 30c and arcuate cutting edges 32a to 32c. That is, the straight cutting edges 30a to 30c extend in a straight line with the vicinity of the rotation center O as a base point and extend to the points intersecting the edges of the twisted grooves 16a to 16c, respectively. The arcuate cutting edges 32a to 32c are curved along the edges of the twisted grooves 16a to 16c so as to be recessed in a direction opposite to the direction of rotation of the drill 10 shown by the arrow A.

In this case, as shown in FIG. 3, when the tip 24 is viewed from the axial direction of the drill 10, the rotation center O is used as a starting point, and the tip 24 is divided into three equal parts by a predetermined angle θ. considering the second reference lines S ₁ inclined by the rotation direction, the straight cutting edge 30a so as substantially coincides with the straight line l which is translated from the second reference lines S ₁ only rotational direction by a predetermined distance t To 30c are preferably formed.

The drill according to the present invention is basically constructed as described above. Next, its operation and effect will be described.

With respect to a main shaft (not shown) connected to a rotary drive source (not shown), for example, a shank portion 14 via a chuck holder or the like.
, And connect the drill 10. When the rotary drive source is started, the drill 10 rotates at high speed in the direction of arrow A in FIG. Therefore, when the tip portion 24 of the drill 10 is brought into contact with a work (not shown) and the work is displaced along the axial direction of the drill 10, the tip portion 24 of the drill 10 starts cutting the work.

That is, the straight cutting edges 30a to 3 formed on the tip portion 24.
0c and arcuate cutting edges 32a to 32c bite into the work,
This is cut as the drill 10 rotates.

According to the present embodiment, as can be easily understood from the description of the configuration of the drill 10, the tip end portion 24 is formed with the cut grooves 28a to 28c, which is so-called thinning. Since the chisel edge portion 26 is set narrow, the cutting resistance received from the work during cutting is relatively small.
Further, since the three cutting edges 22a to 22c are provided, the cutting balance becomes good, and the highly efficient cutting process can be performed. In this case, the chips generated during the cutting process are, for example, even if the chips are relatively long and large chips, the straight cutting blades 30a to 30c and the arc-shaped cutting blades 32a to 32c are divided at a contact portion, and therefore the twist groove 16a is formed. Through 16 to 16c, it will be easily discharged to the outside. Therefore, the chips are drilled
It is possible to avoid the inconvenience that the chip efficiency is significantly reduced by being entangled with the body 12 of 10.

Next, FIG. 4 shows another embodiment of the drill according to the present invention. In this case, the same reference numerals as those in the above-mentioned embodiment indicate the same components.

That is, in this embodiment, chamfering is performed along the blade edges of the straight cutting edges 30a to 30c and the arcuate cutting edges 32a to 32c in the tip end portion 24 of the drill 10, and the negative lands 34a to 3c.
Forming 4c.

As is clear from the sectional shape of the straight cutting edges 30a to 30c in the cutting direction in FIG.
34a to 34c are formed to have a predetermined negative rake angle α with respect to the cutting direction. Thus negative land 34
By forming a to 34c, the straight cutting edge 30a to 3
It is possible to prevent chipping at the 0c and the arcuate cutting edges 32a to 32c. Further, as shown in FIG. 5b, since the ends of the negative lands 34a to 34c converge toward the rotation center O of the chisel edge portion 26,
Chisel edge part 26 where chipping is most likely to occur
Is effective in preventing chipping.

[Advantage of the Invention] As described above, according to the present invention, in a drill having three or more cutting edges, the tip end of the drill is thinned to form the chisel edge portion as narrow as possible. The cutting edge is composed of an arcuate cutting edge and a straight cutting edge. As a result, it is possible to reduce the cutting resistance at the tip of the drill, and improve the chip discharge performance, which has hitherto been a problem of a drill having three or more cutting blades, and therefore highly efficient cutting. The effect that it becomes possible to achieve is obtained.

Further, if the negative land is formed along the edge of the arcuate cutting edge and the straight cutting edge, it is possible to prevent chipping especially at the chisel edge portion of the drill tip. Therefore, it has a remarkable effect in improving the durability.

Although the present invention has been described with reference to the preferred embodiment, the present invention is not limited to this embodiment.
Needless to say, various improvements and design changes can be made without departing from the gist of the present invention, for example, by constructing the cutting blade with five blades.

[Brief description of drawings]

FIG. 1 is an explanatory view showing a tip shape of a drill according to the prior art, FIG. 2 is a side view showing a shape of a drill according to the present invention, and FIG. 3 is a shape of a tip portion of the drill according to the present invention. Fig. 4 is an end view for explaining, Fig. 4 is an end view for explaining the shape of the tip portion in another embodiment of the drill, and Fig. 5a is an explanatory view of a negative land formed on a cutting edge in the drill for another embodiment. 5b is an enlarged conceptual view of the central portion of the drill in FIG. 10 …… drill, 12 …… body 14 …… shank part, 16a ～ 16c …… twisted groove 24 …… tip part, 26 …… chisel edge part 28a ～ 28c …… cutting groove, 30a ～ 30c …… straight cutting edge 32a to 32c …… Arc cutting edge 34a to 34c …… Negative land

Claims (2)

[Scope of utility model registration request] 1. A drill having three cutting blades, which comprises a body and a shank portion having thinned cutting edge tips, wherein the cutting edge tips are forward in a rotation direction from a rotation center O of the drill. The first part that deviates by a predetermined distance t to divide the tip into three equal parts
It is orthogonal to the second reference line S ₁ which is inclined forward by a predetermined angle θ with respect to the reference line S, and is located at a position beyond a virtual straight line passing through the rotation center O, and extends linearly from the cutting edge tip. A straight cutting edge having a negative rake angle in the radial direction whose end point is the intersection point with the end edge of the twist groove formed in the body, and a radial direction continuous from the intersection point along the end edge. A drill characterized in that it is formed with a circular arc-shaped cutting edge having a negative rake angle. 2. The drill according to claim 1, wherein a negative land having a negative rake angle is formed along the edges of the straight cutting edge and the arcuate cutting edge.