Cutting bit, cutting tool and method for machining,...

Cutters – for shaping – Including tool having plural alternatively usable cutting edges – With integral chip breaker – guide or deflector

Reexamination Certificate

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C407S116000, C081S003440

Reexamination Certificate

active

06632051

ABSTRACT:

BACKGROUND OF THE INVENTION
The present invention relates to a cutting bit, a cutting tool and a method for machining.
Similar cutting bits, cutting tools and a machining method for use therewith are described in German Patent Application No. 41 35 681 and the corresponding European Patent Application No. 542 026.
That publication describes an apparatus and a method for machining rotationally symmetrical work piece surfaces, wherein various cutting bits are arranged along a disc-shaped tool carrier and are engaged successively with the work piece for machining. Therein, final machining is in the form of a roughing-down and smoothing operation during which a cutting bit with a substantially zigzag main cutting edge, i.e. formed by projecting and recoiling sections of the cutting bit, is advanced firstly in a radial direction, and then in a roughing-down operation a certain layer thickness is taken off the work piece surface for machining, whereupon the tool is then moved axially in order to perform a smoothing operation by means of which fine machining is effected.
U.S. Pat. No. 4,867,616 discloses a cutting bit which has the basic form of a prism, comprising two substantially parallel top and bottom surfaces and four lateral surfaces substantially perpendicular to the top and bottom surfaces, wherein cutting edges are formed at the transition of the lateral surfaces to the top and bottom surfaces, and wherein those lateral surfaces are not even, and, in the plan view onto the top surface or bottom surface, has alternate projecting and recoiling sections, wherein effective sections of main cutting edges are formed in the region of the projecting sections, and wherein secondary cutting edges extend from the relatively projecting sections of the main cutting edges rearwardly along the recoiling sections at least by a predetermined insertion depth.
With that cutting bit, the secondary cutting edges are bent relative to the main cutting edges partially by 60° and in the corner regions by 45° Furthermore, the machining surfaces are formed by recesses which are associated individually with each section of main cutting edge, wherein in the central region of a main cutting edge an angle of between 62° and 72° results between the machining surface and the main free surface.
Corresponding cutting bits are mounted on a milling cutter in such a way that their main cutting edges slightly overlap, and the main cutting edges of a cutting bit alternatingly cover over the recoiling regions of a successive cutting bit, so that the secondary cutting edges only engage with the tool by way of their regions which are directly adjacent to the main cuts. A corresponding tool is provided exclusively for feed in a radial direction, for the purpose of milling grooves, or the like, in a tool, for example.
OBJECTS AND SUMMARY OF THE INVENTION
In the face of this prior art, the aim of the present invention is to create a cutting bit, a cutting tool, and a corresponding method for machining work pieces, wherein the cutting bit is intended to be fed not only radially but also axially during machining the work pieces, and wherein the corresponding work piece surfaces should be of good quality and efficiently produced, i.e. within strict tolerances.
The selection of special angles firstly permits a positive cutting geometry both during radial and axial feed to the work piece, and, additionally, the reaction forces occurring are kept relatively low, so that neatly defined work piece surfaces can be produced within strict tolerances.
The design of the cutting bit according to the invention enables the cutting bit to be inclined somewhat downwardly relative to the feed direction, wherein a free surface is prepared for improved radial feed of the cutting bit to the work tool or to the work piece surface for machining, on the one hand, whilst it is still possible to maintain a positive cutting edge geometry whereby the cutting forces occurring are reduced.
With respect to a corresponding tool, the problem forming the basis of the invention is solved in that in the tool a corresponding cutting bit is used, and in that the tool seat has a supporting surface for the top or bottom surface of the cutting bit, which is inclined such that it falls away at an angle of between 8° and 12° relative to the radial feed direction.
The corresponding method uses a cutting bit and a cutting tool of the afore-mentioned kind, wherein the radial feed of the cutting bit towards the work piece surface is such that the top and bottom surfaces are inclined such that they fall away to the front relative to that feed direction.
The terms, “radial feed direction” and “axial direction” refer herein, first and foremostly, to a work piece which is rotating about an axis, so that during machining a rotationally symmetrical surface is produced on that work piece. Therein, the feed generally takes place in such a way that the cutting edge and the axis of rotation of the rotating work piece lie in a common plane, and feed of the cutting bit also takes place exactly in that plane, initially in a radial direction. After the desired diameter of the rotationally symmetrical work piece has essentially been obtained, the cutting bit moves axially relative to the work piece for fine machining to ensue, and, in particular, the regions which initially were still remaining between the interrupted main cutting edges are removed by axial rotation.
However, the invention can be extended thoroughly to machining methods in which non-rotationally symmetrical surfaces, e.g. even surfaces, are machined, and the cutting bit is accordingly arranged on a rotating tool. In such a case, the terms, “radial feed” and “axial feed” are defined in relation to the axis of rotation of the tool.
According to the invention, the complementary angle cc between the machining surface and a plane which is perpendicular to the plane of the free surfaces of the main cutting edges is between 14 and 18°, and, with a preferred embodiment, it is 16°.
This means, for example, that in the case of the preferred embodiment mentioned latterly, the seating for the cutting bit, or the top and bottom surfaces of the cutting bit can be inclined at an angle of approximately 10° relative to the feed direction, wherein a positive machining angle of approximately 6° nonetheless remains in the region of the main cutting edge. The inclination of the top and bottom surfaces by approximately 10° relative to the feed direction means at the same time that the plane of the free surfaces, which, due to the prismatic basic form of the cutting bit, extends substantially perpendicularly to the top and bottom surfaces, is likewise inclined by 10° relative to a tangent on the work piece surface in the region of the active main cutting edge, so that an effective free angle of about 10° is formed. It will be appreciated that in the case of a rotating work piece surface because of the curvature of the surface generated the free angle becomes increasingly larger directly behind the cutting edge.
This cutting geometry and arrangement of the cutting bit produce very small cutting forces so that harmful vibration of the work piece, such as can occur with different cutting edge geometries, is largely avoided. At the same time, wear to the cutting edge is reduced.
In addition, the geometry of the cutting bit which is actually selected enables main cutting edges
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to be formed both at the transition of the respective lateral surface to the top surface as well as at the transition of that lateral surface to the bottom surface of the cutting bit. Therefore, after one of the main cutting edges of the cutting bit has become worn, the cutting bit can be turned and used again. This effect is rendered two-fold in a preferred embodiment of the invention wherein the cutting bit has the basic form of a cuboid with two shorter lateral surfaces and two longer lateral surfaces, wherein cutting edges are formed on each of two oppositely disposed lateral surfaces, and, to be more exact, at the transition to the top and bottom surface res

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