JPH04171108A - Drill bit - Google Patents

Abstract

PURPOSE:To drill a hole into a completely circular shape in a drill bit for drilling an iron plate or the like by providing a part having the same radius as that of a rake angle part on a side which is opposite to the above part at sight from the rake angle part with a central axis put between them, and establishing a dimension from the outer periphery of a part except both the rake angle parts to the central axis to be less than the above radius. CONSTITUTION:The cutting part 10 of a drill bit 1 is provided with plural stepped parts 12, different in a diameter, whose tips are thinned and mutually connected through tapered parts 13. The sectional shape of the cutting part 10 is formed into an elliptical shape having a line passing a rake angle part 3 and a central axis (O) as a major axis in disregard of a grooved part 2. Namely, a part having the same radius r2 as the radius r1 of the rake angle part 3 is provided on a side which is opposite to the rake angle part 3 with the central axis (O) put between the above parts, and dimensions from the central axis (O) of parts except the rake angle part 3 and the above part are established to be less than the radiuses r1, r2. This formation makes a diameter in a cutting line coincide with the diameter of the drill bit to produce a hole having a completely circular shape.

Description

[Detailed description of the invention] [Industrial application field]

The present invention relates to a drill bit used for drilling holes in iron plates and the like.

[Conventional technology]

As this kind of drill bit 1, US Patent No. 3゜076
．． There is one shown in the specification of No. 356. As shown in FIGS. 3 and 4, an axial arm 2 is formed on the outer peripheral surface of a tapered drill bit 1, and one side edge of the arm 2 is formed into a rake corner 3. When the radius of the rake corner 3 is 'R, the radius of the other parts is R2 (R2<R1).

[Problem to be solved by the invention]

In this case, since the radius of the portion excluding the rake corner 3 is R2 smaller than the radius R1 of the rake corner 3, that is, the substantial diameter of the drill bit 1 is 2R2, and the rake corner 3 is smaller than the radius R1 of the rake corner 3. Since the diameter 2RI of the cutting line determined by the radius R1 of There is. The present invention has been made in view of these points, and its purpose is to provide a drill bit that can perform drilling operations smoothly and that can drill perfectly circular holes. .

[Means to solve the problem]

Accordingly, the present invention provides a drill bit in which an axial groove is formed on the outer circumferential surface of the cutting part whose diameter gradually decreases toward the tip, and one side edge of this groove is used as a rake corner. A part with the same radius as the radius at the corner is provided on the opposite side of the center axis when viewed from the rake corner, and the dimension from the outer peripheral surface to the center axis of the part excluding both is made smaller than the above radius. It has characteristics. [Function] According to the present invention, since the diameter of the cutting line determined by the radius of the rake corner matches the substantial diameter of the drill bit, no rattling occurs during drilling work. . “Example” The present invention will be described in detail based on the illustrated example below.
The drill bit 1 shown in the figure has a cutting portion 10 in which a plurality of step portions 12 having different diameters are arranged in order of diameter so that the tip becomes narrower, and adjacent step portions 12 are connected by a tapered portion 13. It is a stepped type, and an axial edge 2 is formed on the outer peripheral surface of the cutting part 10 so as to pass through a plurality of steps 12 and a tapered part 13, and a rake angle is formed on one side edge of this groove 2. Section 3 is provided. The cross-sectional shape of the cutting part 10 in this drill bit 1 is an ellipse whose major axis is a line passing through the rake corner part 3 and the central axis 0, as shown in FIG. 2, if the groove part 2 is ignored. When the radius of the rake corner 3 (dimension from the center axis 0 to the rake corner 3) is r, the rake corner 3
Radius r2 on the half-body side sandwiching the central axis 0 when viewed from
(Dimensions from the central axis O) should be r, = r2, and the outer circumference from the central axis 0 of the part excluding these two places □
The dimension to the surface is smaller than r l + r 2 . This means that the diameter 2r+ of the cutting line determined by the radius r of the rake corner 3 and the substantial diameter 2rz of the cutting part 10 match. Therefore, when holding the mounting shaft part 11 of the drill bit 1 with a chuck such as an electric drill and drilling with this drill bit 1, there is no wobbling caused by the difference in radius, and it is possible to keep a perfect circle. It is something that can make holes. Although a stepped type is shown here, it goes without saying that a tapered type as shown in FIG. 3 may be used. [Effects of the Invention] As described above, in the present invention, since the diameter of the cutting line determined by the radius of the rake corner matches the substantial diameter of the drill bit, there is no wobbling during the drilling operation. Not only can the drilling operation be performed smoothly without causing any blemishes, but also it is possible to drill a perfectly circular hole.

[Brief explanation of drawings]

FIG. 1 is a side view of an embodiment of the present invention, FIG. 2 is a sectional view taken along line X-X in FIG. 1, FIG. 3 is a side view of a conventional example, and FIG. 4 is a Y-- It is a Y-line sectional view, and 1 is a drill bit;
2 indicates a groove, and 3 indicates a rake corner. Agent Patent Attorney Ishi 1) Long Nanaema ← 1 @ He -

Claims (1)

[Claims] (1) A drill bit in which an axial groove is formed on the outer peripheral surface of the cutting part whose diameter gradually decreases toward the tip, and one side edge of this groove is used as a rake corner,
A part with the same radius as the rake corner is provided on the opposite side of the center axis when viewed from the rake corner, and the dimension from the outer peripheral surface to the center axis of the part excluding both is made smaller than the above radius. drill bit.