High speed burnishing drill

Cutting by use of rotating axially moving tool – Tool or tool with support – Having inversely angled cutting edge

Patent

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Details

408224, 408229, B23B 5102

Patent

active

051121670

DESCRIPTION:

BRIEF SUMMARY
TECHNICAL FIELD

The present invention relates to a reamer section drill and more particularly to an improved high-speed burnishing drill.


BACKGROUND ART

Various types of drilling tools are known which are adapted to ream a hole of a desired diameter while cutting the wall of the hole. Such drilling tools are a single-purposed, exclusive and/or automated tool which can be increased in cutting efficiency and used to provide high-quality and uniform products.
Japanese Utility Model Application laid open under Kokai publication No. 62-65107 discloses a reamer section drill including two drilling edges and four reaming edges, all these edges being arranged in the same circle.
FIGS. 11 and 12 in the accompanying drawings show another burnishing drill. Such a burnishing drill comprises a cylindrical drill body 2 connected with a shank 1, the drill body 2 includes cutting edges 5, formed therein, at the tip 3 thereof, and opposed to each other diametrically about the longitudinal axis of the drill body 2. Each of the cutting edges 5 includes a slant face 6 extending therefrom rearwardly in the direction of rotation (indicated by arrow A in FIG. 12) and a guide face 7 axially extending from the edge of the slant face 6. The drill body 2 further includes a longitudinally extending relief surface 8 formed therein between each of the cutting edges 5 and the corresponding guide face 7 at the outer wall of the drill body 2 and a longitudinally extending relief groove 9 formed in the drill body 2.
This drill does not have good centering and stabilizing properties since the initial bite cannot be properly made. As a result, the drilled hole made is excessively reamed and its inner wall is rough. This drill often generates a built-up edge.


SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide an improved high-speed feed-type burnishing drill which will not ream the drilled hole excessively and can provide a drilled hole with a smoother inner wall.
Another object of the present invention is to provide an improved high-speed feed-type burnishing drill which is superior in the fusion-resistance, thereby improving the centering and stabilizing properties.
Another object of the present invention is to provide a burnishing drill which is available for reuse by polishing the tip of the drill body.
To this end, the present invention provides a high-speed burnishing drill comprising a shank and a cylindrical drill body connected at one end with the shank.
The opposite end of the drill body has a pair of drilling edges opposed to each other diametrically about the longitudinal axis of the drill body from the center of the forward end of the drill body. Also, the drilling edges incline in an axially rearward direction with a first cutting angle, the outermost margins of the drilling edges being on a reduced-diameter portion having its diameter smaller than the maximum external diameter of the drill body. A pair of reaming edges is formed on the plane intersecting the other plane including the drilling edges about the longitudinal axis of the drill body and these reaming edges extend radially outward from a position inward of the outermost peripheral wall of the drilling edges. The reaming edges also incline axially in the forward direction with a second cutting angle. A reduced-diameter portion of the drill body extends axially backward from the outermost peripheral wall of the drilling edges. An enlarged-diameter guide face is formed on the drill body to extend from a slope formed at a position behind the corresponding drilling edge in the rotational direction toward the shank. The axially forwardmost end of the enlarged-diameter guide face is located at a position axially behind the corresponding reaming edge.
The high speed burnishing drill of the present invention may include the reaming edge connected with a slant face which is inclined axially backward as the slant face extends backward in the rotational direction.
The high speed burnishing drill of the present invention may include the r

REFERENCES:
patent: 3977807 (1976-08-01), Siddall
patent: 4605347 (1986-08-01), Jodock et al.
patent: 4944640 (1990-07-01), Suzuki et al.

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