Cutting by use of rotating axially moving tool – Tool of specific diverse material
Patent
1991-08-22
1993-07-20
Bishop, Steven C.
Cutting by use of rotating axially moving tool
Tool of specific diverse material
407119, 408213, 408713, 408714, B23B 5100
Patent
active
052288129
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The present invention relates to a drill which is mainly applied to piercing steel, and more particularly, it relates to the structure of and materials for a throw-away tipped drill whose insert portion is separably mechanically connected with a shank portion.
BACKGROUND INFORMATION
A drill is a cutting tool which can be used for piercing steel products and the like. For example, the structure of a twist drill is shown in FIG. 1. The twist drill is formed by a cutting portion 1 which is applied to piercing, and a shank portion 2 which is not concerned in cutting but is mainly used for discharging chips and to be clamped in a chuck on the shaft of a drilling machine.
In general, materials for drills are high-speed steel (rapid tool steel) and cemented carbide. The high-speed steel, which has an excellent toughness but is inferior in its wear resistance, is improper for high-speed cutting. On the other hand, the cemented carbide, which has an excellent wear resistance and accuracy characteristics as a tool but is quite brittle and hence may break when used in a machine tool having low rigidity, for example.
In order to improve drills there has been considered a drill structure with a coating of hard TiN on the cutting portion made of high-speed steel, or a drill structure with a cutting portion made of cemented carbide and brazing the same. There have further been devised different connecting structures e.g. by brazing different materials of cemented carbide (P30 and D30) for improving the wear resistance and toughness, (Japanese Utility Model Laying-Open Gazette No. 58-143115) or a structure of metallurgically attaining an integration or connection (Japanese Utility Model Laying-Open Gazette No. 62-46489), or a structure that takes into account the difference between the characteristics required for a central portion and an outer peripheral portion of a drill and preparing the central portion and the outer peripheral portion from different materials of cemented carbide in a double structure (Japanese Patent Laying-Open Gazette No. 62-218010), or a method of forming such a double structure by injection molding (Japanese Patent Laying-Open Gazette No. 63-38501 or 38502). Further, there is a structure of forming the material for a drill as a cermet, in order to improve adhesion resistance of the drill (Japanese Patent Laying-Open Gazette No. 62-292307).
A cutting portion and a shank portion of a drill are exposed to different loaded conditions in a drilling operation. Therefore, characteristics required for the respective portions of the drill are different from each other. For example, wear resistance, adhesion resistance and the like are required for a cutting edge of the cutting portion, while toughness for maintaining the strength of the tool is required for the shank portion. Further, different cutting edge characteristics are required for different portions along the cutting edge since cutting speeds are different at the center and at the outer peripheral portions of a drill cutting edge.
In a drill whose cutting edge is coated in order to satisfy these different requirements at least a coating layer of a front flank side is inevitably removed when resharpening the drill as is performed in general, whereby most of the coating effect is lost. A drill having such a structure that cemented carbide is brazed to its cutting portion cannot be used for deep hole drilling of a hard to cut material since brazing itself is a method which is essentially inferior in thermal strength and mechanical strength. Further, when cemented carbide is brought into a coarse grain state or a high binder phase state in order to improve the toughness of the shank portion of a drill, the strength of the material is reduced or the elastic limit of distortion is reduced, and hence the shank portion is undesirably broken during drilling, due to vibration of a workpiece, unstable rotation of a drive shaft and the like. Also, the cost of a drill having a large diameter and a long length for drilling deep holes
REFERENCES:
patent: 4113503 (1978-09-01), Lumby et al.
patent: 4293253 (1981-10-01), Ott
patent: 4527931 (1985-07-01), Sarin
patent: 4744704 (1988-05-01), Galvefors
JIS (Japan Industrial Standard) B0171-1609.
Isobe Kazutaka
Kitagawa Nobuyuki
Mori Yoshikatsu
Noguchi Kazuo
Nomura Toshio
Bishop Steven C.
Fasse W. G.
Sumitomo Electric Industries Ltd.
LandOfFree
Throw-away tipped drill does not yet have a rating. At this time, there are no reviews or comments for this patent.
If you have personal experience with Throw-away tipped drill, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Throw-away tipped drill will most certainly appreciate the feedback.
Profile ID: LFUS-PAI-O-1757098