Cutting insert and drilling tool for drilling in solid materials

Details Cutting insert and drilling tool for drilling in solid materials Cutting insert and drilling tool for drilling in solid materials

1994-01-31

1996-04-02

Howell, Daniel W.

Cutting by use of rotating axially moving tool

Tool-support with means to permit positioning of the tool...

Pivotable tool

408194, 408211, 408224, 408713, B23B 5102

Patent

active

055035094

DESCRIPTION:

BRIEF SUMMARY
CROSS REFERENCE TO RELATED APPLICATIONS

This application is a national phase of PCT/DE 92/00562 filed 7 Jul. 1992 and based, in turn, on German national application P 41 26 241.7 of 8 Aug. 1991 under the International Convention.


FIELD OF THE INVENTION

The invention relates to a cutting insert for drilling and, more particularly, to a cutting insert with at least three cutting angles delimiting the cutting face and with cutting edges lying between two adjacent cutting angles.
Further the invention relates to a drilling tool with a shaft and at least two replaceable, geometrically similar cutting inserts each having several cutting edges and arranged in a recess on an end of the shaft, these inserts being arranged at various radial distances on the shaft, their work ranges bordering on each other and partially overlapping, whereby each cutting insert has cutting edges with mutually inclined cutting edge areas which, when in operation, are all simultaneously engaged, whereby the radially innermost cutting plate borders directly on the drill axis or extends slightly beyond it.
Cutting inserts are known in many basic shapes, such as hexagonal, octagonal, pentagonal, triangular, round, rhomboidal and rectangular cutting plates, in some cases with increased corner angles. Particularly for drilling in solid materials hexagonal cutting plates are used, wherein two cutting edges include an obtuse angle of 120.degree. to 170.degree. for chip removal. The use of such cutting plates is described in DE 27 30 418 C2. In this system the cutting plates are each arranged in a recess of the drill shaft, so that the angle bisecting line of the engaged cutting edges is parallel to the drill axis or at a slight tilt thereto of a maximum of 2.degree..
The disadvantage of this drill is that an equilibrium of forces of the drill shaft can be established only when each two engaged cutting edges of a cutting plate are substantially engaged over their full lengths and the work ranges of neighboring cutting edges do not overlap. Furthermore, when the drilling diameter is changed, a new set of cutting inserts has to be used.
The same applies also when cutting inserts described in EP 0 181 844 B1 are used. These inserts in a top view show an approximately rectangular contour, whereby on opposites sides there are two cutting edge pairs arranged at a obtuse angle.
In EP 0 054 913 B1 it is proposed to arrange the receiving recesses for individual indexable inserts in such a way that the radial cutting force components of the engaged cutting edges balance themselves out for each separate indexable insert, because angle bisecting lines of these cutting edge are inclined to parallels to the drill axis by an angle which depends on the effective length of the cutting edge engaged along a section.
In order to compensate the radial forces in DE 27 51 255 C2 it has also been proposed to angle the radial plane of the inner cutting insert backwards with respect to the peripherally arranged cutting insert by a certain angle, against the direction of rotation of the drill, in order to compensate for the radial forces acting on the drill shaft. However this orients the forces parallel to one another, but not compensate them, since the offset angle cannot have any influence on the magnitude of the radial and the cutting forces. Thus the forces are maintained as a function of the cutting conditions, not depending on the geometry of the tool.
Finally DE 38 02 290 C1 describes a drill for drilling through plate stacks, but also through monolithic solid material, to arrange a first indexable insert radially outside on a diameter beyond the half defined by the drill axis, and on the opposite side two smaller indexable inserts, whereby the effective outer cutting edge of the radially outer indexable insert runs approximately on the same work cone and on the same maximal radius as the radially outer cutting edge of the largest indexable insert. Also with this arrangement only a radial cutting force balance can be achieved.
In addition all of the aforement

REFERENCES:
patent: 4648760 (1987-03-01), Karlsson et al.
patent: 4889455 (1989-12-01), Karlsson et al.
patent: 4889456 (1989-12-01), Killinger

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