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
1993-11-19
1995-06-20
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
408201, 408225, 408233, 408705, B23B 4102, B23B 5100
Patent
active
054256046
DESCRIPTION:
BRIEF SUMMARY
FIELD OF THE INVENTION
The invention relates to a drilling tool for machine tools comprising a shank having at least one chip groove, a drilling crown preferably removably arranged on the front face on the shank and having at least two regions with partially cylindrical circumferential surfaces, a corresponding number of chip channels adjoining the regions and being essentially axially parallel aligned and ending rearwardly into the associated chip groove, and at least two cutting plates which are arranged at a radial distance from the shank axis with work areas that at least partially radially overlap one another in each other recess of the regions in the area of the chip channels and each of which has at least one active cutting edge projecting at the front face over the drilling crown with the cutting edge of the radially outermost cutting plate radially extending over the partially cylindrical circumferential surfaces.
BACKGROUND OF THE INVENTION
A drilling tool of this type is known (AT-B-383070) in which, through a special alignment of the cutting plates which partially overlap one another in the effective range of their cutting edges, care is taken that the transverse forces existing at the cutting edges during the drilling operation are essentially cancelled so that bores or holes can be created in a workpiece without any guidance. However, problems arise when during drilling through a workpiece or through a stack of plates the automatic centering by the cutting plates does not take place and the tool hits with the circumferential surfaces of the drilling crown against the edge of the bore. This can result, mainly in the case of great boring depths over 4.times.D (D=drill diameter), in damage to the workpiece or the drilling tool.
Based on this, the basic purpose of the invention is to further improve the drilling tool of the above-disclosed type so that it can also carry out drillings at great boring depths.
SUMMARY OF THE INVENTION
To attain this purpose the invention suggests that in the area of at least one of the partially cylindrical circumferential surfaces at an axial distance from the drilling crown front face there is arranged a guide element radially projecting slightly less than the cutting edge of the radially outermost cutting plate. According to a preferred embodiment the invention, two guide elements are provided which are spaced from one another at an angular distance differing from 180.degree. and are spaced advantageously at an axial distance from one another. The drilling crown has advantageously two diametrically opposed chip channels or regions, while the cutting plates are spaced individually or in pairs at an angular distance of approximately 180.degree. from one another.
The guide elements of the invention ensure that the tool, during drilling within the bore, is guided on the wall of the bore without the circumferential surfaces of the drilling crown hitting the outer edge of the bore. When drilling through workpieces with an inclined rear surface an additional problem arises, namely the drill initially exits the bore on one side thereof while the drill is still guided in the bore above the opposite circumferential part. The incline can thereby be such that the inventive guide elements of the drilling crown already have exited through the earliest point of exit before the workpiece has been completely drilled through. This causes the drill to be deflected and to hit with its shank against the wall of the bore in the area of the earliest point of exit. The problem exists thereby that the cutting plates, which are still engaged, are being destroyed. Furthermore, the bore is not fully produced and the wall of the bore is destroyed in the area of the point of exit. In order to avoid this disadvantage, it is suggested according to a preferred embodiment of the invention that a further guide element is arranged at an axial distance from the guide element or one of the guide elements in the area of the partially cylindrical circumferential surfaces, and that the axially ad
REFERENCES:
patent: 3816018 (1974-06-01), Hlocky
patent: 3942905 (1976-03-01), Gill et al.
patent: 3963365 (1976-06-01), Shallenberger et al.
patent: 4248555 (1981-02-01), Satou
patent: 4264246 (1981-04-01), Lowis et al.
patent: 4353670 (1982-10-01), Jorgensen
"Wendeplattenbohrer Fur Grosse Bohrtiefen", by Ulrich Krenzer, Werkeuge (Aug., 1990), pp. 38-40.
Perthen Rainer
Scheer Gerhard
Bishop Steven C.
Komet Praezisionswerkzeuge Robert Breuning GmbH
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