Cutting by use of rotating axially moving tool – With work-engaging structure other than tool or tool-support – Frictionally engaging sides of opening in work
Patent
1996-06-11
1998-10-13
Bishop, Steven C.
Cutting by use of rotating axially moving tool
With work-engaging structure other than tool or tool-support
Frictionally engaging sides of opening in work
1753251, 175399, 411 16, 411396, 4119291, 408143, 408705, B23B 4102, B23B 5100
Patent
active
058203168
DESCRIPTION:
BRIEF SUMMARY
BACKGROUND OF THE INVENTION
The invention relates to a guide element for a cutting tool. The problem with cutting tools, in particular when cutting bores of a large diameter, is that the cut does not run concentrically and that it is therefore not always possible to make a perfectly cylinder-shaped bore hole. Instead, the bore hole has an irregular polygonal profile. This "non-round" cross-section of the bore hole is transferred back to the tool during further machining operations. As a result, the tool does not run "round", but instead, due to the irregular cross-section of the bore hole, it continually swings out of concentricity and tries to follow the irregular polygonal course. Furthermore, in the case of long narrow cutting tools, the cutting forces that arise through the inherent rigidity of the tool cannot be satisfactorily contained. This can result in critical strain on the tool.
In order to minimize the described irregular course of the tool and to prevent critical strain on the tool, the prior art uses guide elements on the external sides of the tool. These guide elements support the tool in a radial direction on the internal walls of the bore hole already created by the leading cut in each case. This support provides the tool with additional stabilization against deformations and also effectively reduces the undesired irregular course of the tool.
In order to improve the concentricity of the tool, the prior art publication DE-A42 14 528, for example, discloses a pilot or center drill being attached to the main cutter. This pilot or center drill centers the tool in the bore hole. The problem, however, is that, as the tool is being removed from the bore hole, the pilot or central drill comes out of the pilot or central bore hole, with the result that the tool again tends to run irregularly while it is being removed. For this reason, this prior art tool also has the afore-mentioned guide elements arranged radially on the peripheral edges of the tool. The disadvantage of these prior art guide elements is that they are complicated to assemble. Even the insertion of the guide elements into the tool presents assembly problems. In addition, it is very difficult to set and adjust the tools.
For finish cutting, the surface and the form evenness is usually very good. There is therefore not very much strain on the guide elements. In the case of rough cutting, however, problems with the guide elements often arise as a result of both the bore surface as well as the unevenness of the bore shape. In particular, problems arise when boring with bore tools that are equipped with indexable inserts. The surface of the bore internal wall becomes severely scratched as a result of the large volume of chips that occur through the cutting. The surface quality of the bore hole is therefore greatly reduced. Surface flaws that occur in this way cause the guide element to run irregularly on the bore internal wall, thereby giving rise to undesired natural vibrations in the tool. Moreover, the large volume of chips means that the chips push the tool away from its rotating longitudinal direction and cause the tool to run in a "non-round" manner. Both effects cause flaws in the contour or the shape of the bore hole.
As a result, the guide elements following the cutters in each case have to be sufficiently robust and shock-resistant to withstand the mechanical strain caused by the flaws. In order to prevent abrasion of the guide elements against the bore walls, which become rough through the scratching, the guide elements have to be hard and resistant to wear and tear. In addition, it is advantageous if the guide elements can offset the tolerance errors in size and shape which always occur as a result of changing the indexable inserts.
Finally, long internal-processing tools are often very sensitive to vibrations. However, the guide elements must not transfer the vibrations originating from the cutter to the work piece. Instead, the guide elements should offset as much as possible the vibrations coming from the cutter, or at l
REFERENCES:
patent: 1809620 (1931-06-01), Cole
patent: 2334795 (1943-11-01), Smith
patent: 2874741 (1959-02-01), Brancato
patent: 3529508 (1970-09-01), Cooksey
patent: 4040326 (1977-08-01), Breed
patent: 4096771 (1978-06-01), Monro
patent: 5183358 (1993-02-01), Foulkes, Jr. et al.
patent: 5425604 (1995-06-01), Scheer et al.
Hitz Wolfgang
Krenzer Ulrich
Bishop Steven C.
Kennametal Hertel AG
Vasuta John M.
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