Cutting by use of rotating axially moving tool – With means to apply transient – fluent medium to work or product – Including tool with duct
Patent
1996-10-15
1998-11-03
Bishop, Steven C.
Cutting by use of rotating axially moving tool
With means to apply transient, fluent medium to work or product
Including tool with duct
408 57, B23B 5106
Patent
active
058299262
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
1. Field of the Invention
The invention relates to a drill comprising a shaft, particularly one made of full carbide metal, having cutting edges arranged at the cutting end of the shaft. Additionally, there is a connection area at the outer connecting end of the shaft for connecting with the driving spindle of a machine tool. The shaft has ducts which run parallel to each other through the shaft in a substantially longitudinal direction and open out at the cutting end of the shaft for transporting fluids from the connection end to the cutting edges.
2. Background Information
DE 36 01 385 C2 discloses such a drilling tool. Its helically fluted shaft is preferably made of full carbide metal with an essential characteristic being the helically extending interior ducts for transporting coolant to the cutting edge area at the tip of the drilling tool. The ducts open out at the respective flanks of the cutting edges to bring the coolant to the immediate cutting area and to effect cooling of the drill's cutting edges.
Cooling of the cutting edges presents problems particularly with drilling tools for deep bore holes. Such cooling is especially important in full carbide drills and is effected by cooling lubricants. In metal cutting technology, there is a general trend toward dry operation to avoid the disadvantages of wet operation or wet cutting. These disadvantages include exposure in the work place and problems of waste disposal. However, the high water content of cooling lubricant emulsions can also result in corrosion of the work piece.
An additional problem, particularly with heavy-duty drills and deep bore holes, is meeting their fit accuracy. For this purpose, the drill is provided with tolerance data. With close tolerances, however, tolerance data can guarantee the associated fit accuracy only if there is no excessive temperature rise in the important cutting edge area. Adequate heat removal from the cutting edge area is therefore a basic prerequisite for dry cutting.
It is generally known in cutting technology that the cutting materials silicon nitride and oxide ceramics exhibit a low coefficient of thermal expansion and therefore little sensitivity to heat. Their usability is limited, however, due to the fact that these cutting materials are very brittle. On the other hand, the conventional cutting material, carbide metal, exhibits the disadvantage of increased thermal expansion.
Today, the cutting performance of carbide tools is enhanced by coatings which are particularly effective in the cutting edge region. However, this necessarily results in higher temperatures in the contact zone and correspondingly requires improved heat removal.
Furthermore, JP 1 321 105 discloses a face grinding tool with an approximately tubular shaft, the shaft wall of which is provided with coolant ducts running in axial direction and opening out at the shaft end face. The shaft end openings of two coolant ducts are spatially connected with each other by a ring which is fitted onto the front end of the shaft with a ring groove facing the coolant duct ends to create a coolant loop of a closed coolant circulation system. The end face of this circular ring is fitted with a diamond abrasive body which performs the metal removal with a non-defined cutting edge. The ring which connects the coolant ends with each other is fully admitted to the cutting forces that act on the diamond cutting body. Technically, a grinding process is metal removal with a non-defined cutting edge. As a result, the cutting forces are uniformly distributed over the circumference of the ring and the ring's welded connection with the tubular shaft being able to absorb these uniformly distributed cutting forces. In a drill, by contrast, the cutting forces act on the drill cutting edges which take up a comparatively small part of the drill end face and are therefore usually subject to substantially higher loading than the grinding segments of a face grinding tool.
OBJECT OF THE INVENTION
The object of the invention is to design
REFERENCES:
patent: 4881431 (1989-11-01), Bieneck
John Dernoga, "Internal-Cooled Bits", in American Machinist, p. 66, Apr. 2, 1951.
Bishop Steven C.
Kennametal Hertel AG
Prizzi John J.
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