Cutting by use of rotating axially moving tool – Tool or tool with support – Having stepped cutting edges
Patent
1992-07-28
1994-05-24
Howell, Daniel W.
Cutting by use of rotating axially moving tool
Tool or tool with support
Having stepped cutting edges
408188, 408227, 408713, B23B 5102
Patent
active
053142721
DESCRIPTION:
BRIEF SUMMARY
TECHNICAL FIELD
The present invention relates to a structure of a drill which uses tips.
The present invention can be utilized for every drilling type of work, and in particular, high-efficiency operation for drilling relatively small holes.
BACKGROUND ART
Any of the drills using conventional tips has a relatively large outer diameter in order to maintain the balance of cutting resistance between a central edge and an outer peripheral edge. Described in U.S. Pat. No. 4,586,858 and Published Unexamined Japanese Patent Application No. 62-84912, by the inventor hereof, are drills which use tips of special shapes such that they can drill holes of relatively small diameters, and thus drills which use tips intended for drilling relatively small holes have been known publicly.
In a drill disclosed in U.S. Pat. No. 4,586,858, however, a plurality of tips are arranged constituting cutting edges, and portions without the tips are provided so that the cutting edges are partially discontinuous, whereby left- and right-hand cutting edges are well balanced in cutting resistance. In this case, however, the diameter of each work hole can be reduced by only a limited amount. In a drill described as an alternative embodiment, on the other hand, tips constituting cutting edges are specially worked so that a portion incapable of cutting work is arranged at part of the cutting edge, whereby the cutting resistance is well balanced. In this case, special processing of the cutting edges entails high cost.
Further, in a drill described in Published Unexamined Japanese Patent Application No. 62-84912, tips constituting cutting edges are also specially worked so that a portion incapable of cutting work is arranged at part of the cutting edge, whereby the cutting resistance is well balanced. This drill also entails high cost.
DISCLOSURE OF THE INVENTION
The object of the present invention is to provide a drill of simple construction using commercially available tips, if possible, or minimally modified versions thereof, and applicable to drilling work for small-diameter holes.
In order to achieve the above object, the present invention is arranged so that a half vertical angle formed between the ridge of a center-side cutting edge and the center line of a tool is equal to a half vertical angle formed between the ridge of an intermediate cutting edge on the opposite side and the tool center line, a straight line connecting the middle point of the length of the ridge between the opposite ends of the center-side cutting edge and the middle point of the length of the ridge between the opposite ends of the intermediate cutting edge extends substantially at right angles to the tool center line, the length of the ridge between the opposite ends of the center-side cutting edge is substantially twice that of the ridge between the opposite ends of the intermediate cutting edge, and the ridge of the intermediate cutting edge has a lip height in the direction of the tool axis, above the level of the ridge of the center-side cutting edge, the lip height being greater than 1/2 of the feed per drill revolution. Preferably, moreover, the center-side cutting edge and the intermediate cutting edge are composed individually of tips removably fixed to the body of a drill. Preferably, the tip is formed by uniformly removing the region near each vertex of an equilateral triangular configuration so that each side constitutes a cutting edge. Alternatively, the tip has a rectangular basic configuration, and is formed by uniformly removing each two corresponding vertices on each diagonal so that each side constitutes a cutting edge. Two tips of different sizes are fixed to the drill body so that the respective one sides of the tips constitute the center-side cutting edge and the intermediate cutting edge individually. When increasing the diameter of work holes, tips of the same shape and size having cutting edges are fixed in symmetrical positions outside the center-side cutting edge and the intermediate cutting edge individually.
According to another a
REFERENCES:
patent: 4586858 (1986-05-01), Kubota
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