Cutting insert for shaping by chipping

Details Cutting insert for shaping by chipping Cutting insert for shaping by chipping

1999-11-12

2001-05-01

Wellington, A. L. (Department: 3722)

Cutters, for shaping

Including tool having plural alternatively usable cutting edges

With integral chip breaker, guide or deflector

C407S033000, C408S713000

Reexamination Certificate

active

06224300

ABSTRACT:

FIELD OF THE INVENTION
The invention relates to a cutting insert for shaping preferably by chipping of metallic workpieces with at least one cutting edge extending between two cutting corners and defined by a chipping face and a flank. The cutting edge has two at least partly active cutting edge sections forming an obtuse angle where they merge into each other in the area of a roof-shaped tip, whereby the chipping face has at least one raised shaped chipping element.
BACKGROUND OF THE INVENTION
Cutting inserts with such shaped chipping elements are known, for example from DE-A-44 22 312. The shaped chipping elements end in said reference in front of the cutting edge and extend wedge-shaped in the direction of the cutting edge. The raised shaped chipping elements do indeed achieve separation of the chips from one another at certain points through a purposeful power inclusion so that the stable chip cross section is weakened and the power action coming from the chip into the cutting insert is reduced. Also the chipping characteristics of the conventional cutting insert leave much to be desired in particular during the start of drilling.
Starting out from this, the basic purpose of the invention is to provide a cutting insert for shaping by chipping of the above-disclosed type, which is distinguished through particularly favorable characteristics during the start of drilling through structured chip formation and through quiet chipping.
SUMMARY OF THE INVENTION
The basic idea of the invention is that through a division of the cutting edge into leading and trailing cutting edge portions, there is achieved a soft drilling start and a stable true-to-size boring operation without lateral deflection of the respective tool. To achieve this, it is suggested according to the invention that the raised shaped chipping element extend from the inside of the chipping face to the cutting edge, and thereat extend to form the roof-shaped tip partially over the two cutting edge sections.
A particularly favorable guiding behavior over the entire boring operation is achieved when the edge sections and the adjacent chipping face portions have a step defining the shaped chipping element, and when the cutting edge sections extend preferably continuously risingly from the bottom edge of the step toward the cutting corner. The cutting edge sections reach advantageously in their extent toward the cutting corners essentially the level of the cutting edges in the area of the shaped chipping element. It has proven to be particularly advantageous when the step edges extending over the chipping face form an angle of 90° to 110° with the associated cutting edge section on their sides facing the respective cutting corner, and thereby function as independent additional cutting edges of the shaped chipping element. In order to achieve a dividing of the chips in the area of the shaped chipping step, it can be advantageous when the step surfaces defining the additional cutting edges form an acute angle of 75° to 88° with the adjacent leading chipping face portions. The main and additional cutting edges of the shaped chipping element, which edges lead during the cutting operation, result, because of their supporting function, in a better guiding behavior and in a reduction of vibration creation in particular in the range of upper vibrations with high frequencies, and thus reducing the creation of noise. In order to improve the guiding behavior without a chip division in the area of the shaped chipping element, it is advantageous when the step surfaces defining the additional cutting edges form an obtuse angle of 70° to 88°, preferably 75° to 85°, with the adjacent leading chipping face portions. It has been proven to be particularly advantageous for this purpose when the length of the cutting edge in the area of the shaped chipping element is 15% to 40% of the entire cutting edge length.
To improve the force balance during the cutting operation, it is possible to design the shaped chipping element also asymmetrically with respect to the roof-shaped tip. In particular, it is possible for this purpose that the leading cutting edges and chipping face portions extend declined toward one cutting corner and inclined toward the other cutting corner.
In order to improve the guiding behavior of a boring tool equipped with the cutting elements of the invention, in particular during the start of drilling, it is suggested according to a preferred embodiment of the invention that the equation
h=a·f/
tan &dgr;
is applied to the step height of the shaped chipping element, wherein f is the tool feed per rotation of the machine tool, &dgr; is the clearance angle in the area of the leading cutting edge portion, and a is a factor=0.2 to 1.5, preferably 0.3 to 0.8.
In order to improve the chip formation and chip removal, the chipping faces extend concavely in the area of the shaped chipping element and outside of the shaped chipping element each from the cutting edge initially dropping and then rising up to a plateau remote from the edge. A further improvement in this respect is achieved by the chipping angle continuously decreasing from the step edges of the shaped chipping element toward the cutting corner.
The cutting inserts of the invention are preferably utilized in solid drills or in double cutters with at least two cutting inserts.


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