Cutting by use of rotating axially moving tool – Tool or tool with support – Having peripherally spaced cutting edges
Patent
1997-08-27
2000-01-11
Pitts, Andrea L.
Cutting by use of rotating axially moving tool
Tool or tool with support
Having peripherally spaced cutting edges
408 59, 408145, 408226, 408230, 408233, 408713, B23B 5100
Patent
active
06012881&
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a drilling tool, having a removable drill tip. Various connections between the drill shank and drill tip, as well as various drill tip features are discussed.
BACKGROUND OF THE INVENTION
The twist drill is the most widely used drilling tool for drilling into solid material and bores having a diameter up to approximately 18 mm. The material used in manufacturing twist drills is alloyed tool steel, high-speed steel, and hard metal. If needed, the drill can be coated with a wear-reducing layer of e.g. titanium nitride. Wear occurs mainly in the vicinity of the drill tip in the region of the main cutting edge and at the guide chamfer. In order to eliminate the wear, it has been hitherto known to re-grind the drill at the corresponding flanks. In this, it is found to be disadvantageous that the drill becomes shorter during the grinding operation. In order to avoid this disadvantage, it is further known (DE-C-37 09 878) that the cutting part consists of a base body connected to the drill shank as one part and an exchangeable tip connected to the drill tip as one part, which are connectable to each other in a form- and friction-fitting manner at an axial separation point.
Based on this, it is the object of the invention to improve the known drilling tool of the type described above such that a reduction of wear and an improvement of the drilling quality can be obtained by simple productional measures.
SUMMARY OF THE INVENTION
The invention is based on the idea that with a separation into two parts of the drill in the region of the chip removal part the drill tip can be made of a different, harder material and easily exchanged when used to the limit of wear. In order to achieve this, it is proposed that the exchangeable tip as a whole consists of a material which is harder than the base body. The exchangeable tip advantageously consists of a cutting material from a group of hard metals or ceramics and may, in this case, be made as a sintered powder injection moulded part. The exchangeable tip can also be made of a wear-resistent coated tool steel. The base body on the other hand advantageously consists of tool steel or a high-speed steel.
In a preferred or alternative embodiment of the invention, the main cutting edges each have two cutting edges which are formed into the exchangeable tip, sloped against each other in a roof shape, and aligned in a generally radial direction. The cutting edges of the two main cutting edges can be positioned in equal radial distances from the drill axis, forming a double cutter, so that they are engaged over their full length during the drilling operation. This is advantageous, though, only when one of the two inner cutting edges overlaps with the drill axis. The cutting edge corners which protrude radially over the outer circumference of the drill tip advantageously merge into a generally axially aligned guide edge. The guide edge is adjoined in the circumferential direction by a guide rib which radially protrudes over the outer circumference and extends over part of the circumference of the drill tip. The peak and the outwardly protruding cutting edge corners of the two main cutting edges are positioned in equal radial distances from the drill axis. Accordingly, the outer cutting edges of the two main cutting edges are of equal length, while the inner cutting edges are of different length. In a preferred embodiment of the invention, the cutting edges and a plane which is perpendicular to the drill axis include an angle of 2.degree. to 30.degree., preferably of 8.degree. to 16.degree., so that the pairs of cutting edges of the main cutting edges include a roof angle of 120.degree. to 176.degree., preferably of 148.degree. to 164.degree..
The cutting edges formed into the exchangeable tip may be at least partially bevelled and/or rounded-off and possibly wave-shaped. Further, indentations, raised portions, steps, or ribs, which preferably reach the cutting edges, can be formed into the cutting faces. It is especially advantageo
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patent: 5399051 (1995-03-01), Aken et al.
patent: 5836726 (1998-11-01), Berglund et al.
Komet Praezisionswerkzeuge Robert Breuning GmbH
Pitts Andrea L.
Smith Monica
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