MXPA01008476A - Cutting insert with chip control - Google Patents

Abstract

The cutting insert (10) disclosed is a block of hard metal configured on at least one of its major faces (12, 18) to provide peripheral cutting edges (14) successively indexable about a central fastener (21) location to position each edge seriatim for cutting. The major face slopes downwardly and inwardly from the cutting edges to provide rake surfaces (16) of positive rake behind the cutting edges, and then rises as a sloping ledge (34) to a central boss (24). A series of depressions (32) disposed along the rake surface produce a ribbed chip which breaks more readily, and into smaller chips, easier to flush or otherwise remove from the cutting site.

Description

CUTTING INSERT WITH REBOUND CONTROL Field of the Invention The disclosed and claimed invention relates generally to hard, indexable metal cutting inserts for ductile metals. In particular, it concerns the configuration of the insert harrow face to cut a burr from a work piece of ductile material in such a way as to cause it to break into a short loop over a practical range of feeding rate work, i.e. burrs both thin and thick, to facilitate easy removal of the cutting site. BACKGROUND OF THE INVENTION In general, the interruption of the cutting face of cutting inserts with depressions spaced laterally in the path of the burr from the cutting edge has been appreciated for its ability to make burrs removed from ductile work material. become more susceptible to being broken. The effect of properly positioned depressions is to produce longitudinal ridges in the flash while remaining in a somewhat plastic state due to the high temperature produced by the speed of the forced shear stress of the flash from the work piece. In turn, the spines stiffle the flash against bending and accelerate the achievement of a sufficiently high level of bending or tension stress at a point in the remote burr of the cutting site to cause it to break. The effect varies with the properties of flow of the material, and with the speed of cut and the rate of feeding, that exert influence on the rate of effort and the heat generated in the burr as well as determine its thickness. The aim of this invention is the provision of an insert, suitable for use in drills and other applications, which will break the ductile material burrs into shorter lengths in a practical range of working feed rates and burr thicknesses. SUMMARY OF THE INVENTION The cutting insert of the invention provides a positive tilt harrow surface when mounted on a drill body. The harrow surface moves away from the cutting edge to an inclined spine of considerable height, while the harrow surface itself between the cutting edge and the spine is interrupted by a series of depressions spaced along and adjacent to the edge. Cutting in the burr flow path. The depressions serve to corrugate and curl a sufficiently thin burr to follow its contour as it exits the cutting edge, while the spine behind them serves to curl thicker burrs that are rigid enough to overcome the depressions. BRIEF DESCRIPTION OF THE DRAWINGS The invention is explained in the following description of a preferred embodiment, shown in the following drawings, in which: Figure 1 is an elevational view of a drill using the cutting insert of the invention.; Figure 2 is a bottom end view thereof; Figure 3 is an enlarged isometric view of the insert; Figure 4 is a plan view thereof; Figures 5 and 6 are fragmentary views in sections of the insert, taken in lines 5-5 and 6-6 of Figure 4, respectively; and Figure 7 is a fragmentary, amplified elevation of the bore of Figure 1, in the process of generating the corrugated form of flash produced by the insert of the invention. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT Referring initially to Figures 3 to 6 of the drawings, the cutting insert 10 of the invention, in the preferred form, is a block in the form of a modified parallelepiped, namely a square block, having two main faces, an upper or front face 12 configured to provide the peripheral cutting edges 14 and the associated harrow surfaces 16, and a flat, parallel seating face 18, both limited with smaller lateral surfaces, of identical inclination. The insert is pierced by a central hole 22 in an axis perpendicular to the main faces 12 and 18. The upper or front face 12 of the insert moves away from the peripheral cutting edges 14 as the downward inclining harrow surfaces 16., and then it rises as a surface inclined at approximately forty-five degrees (45 ') with the plane of an elevated central male 24 from which the central hole 22 is counter-driven to seat the customary screw 21 to secure the insert in a suitable cavity in a fluted bore body 23. The downward and inward slope of the harrow surface 16 (Figures 5 and 6) provides a positive harrow with respect to the flattened core 24 and the parallel seating surface 18. smaller, identical lateral surfaces 20 of the block spindle inward from the periphery of the larger upper face of the insert to the lower seat layer 18. This spindle proceeds in two steps, a narrow upper band 26, at a smaller angle with one perpendicular to the lower face, and a wider band 28 at an angle somewhat greater than the perpendicular. The intersections of the lateral and lower surfaces of 1 insert are provided with relief by a slight bevel. The narrow band 26 and the widest band 28 respectively serve as primary and secondary free space surfaces for the cutting edges 14 of the insert at the periphery of its upper major face 12. In the preferred form illustrated, each cutting edge 14, formed at the intersection of the narrow band 26 of the lateral surface and the upper harrow surfaces 16 of the receding insert, is essentially linear, and can be slightly flattened by a cutting edge platform 30. Behind each cutting edge 14 is a series of depressions or "grains" 32 on the harrow surface 16, five behind each cutting edge in the illustrated case. These depressions, in the preferred form, are spherical, their spacing being derived as if an imaginary tangent making contact with spheres of equal size would have been printed on the harrow surface 16 at a depth of 40% of the spherical radius, sufficient to make a crater in the harrow surface of the cutting edge 14 to the base of the peripherally lowered surfaces, inclining upwards 34 of the raised central male 24 in the upper greater surface 12 of the insert. In terms of relative dimensions, the depressions 32 occupy approximately 40% of the area of each harrow surface 16. The height of said loin surfaces relative to the cutting edge is at least as large as the depth of the depressions relative to the cutting edge. to the cutting edges. The spaced-apart spherical depressions 32 of the peripheral dragging surface 16 which moves away from the uppermost major spacer 12, transform the peripheral surface into a variable harrow composite harrow surface along the cutting edge 14, at an angle of positive harrow in the depressions 32 (figure 5) than in the residual harrow surfaces 16 between them (figure 6). The result is the formation of a burr 40 (FIG. 7) which is corrugated or ribbed, with the ribs 42 between adjacent ribs 44 formed by the residual harrow surfaces between the depressions. At the four corners of the insert 10, the junctions of the various peripheral cutting edges 14 are rounded, and the immediately adjacent corner harrow surface 46, distinguished from the positive harrow surfaces 16 by its relatively neutral harrow angle, strengthens the cutting edge in the corner. That aspect of a conventional practice rather than a novel aspect of the invention. When used for drilling, the radially inner end insert particularly benefits, at which relatively lower cutting speeds result in a greater reaction to the cutting force. Typically, two such inserts are mounted in the bore body 28 (FIG. 1) in order to sweep cutting paths that overlap when feeding the bore to a workpiece 46 (FIG. 7). Figure 7 shows a burr 40 being formed by the insert closer to the center of rotation, where the cutting speed is zero at the center of rotation and increases linearly along the cutting edge, resulting in a distinctive conical burr 40. When the feed of the bore 23 in the workpiece 46 is light, say in the order of a cut depth of six thousandths of an inch, the burr tends to follow the curvature of the depressions 32 in the harrow surface 16, and easily curl by going through those depressions. Under conditions of higher feeding rates, say ten thousandths of an inch or greater, the thicker flash tends to pass over the depressions 32 of the harrow face with little conformation thereto. Such thicker burrs hit the sloping spine 34 of the central male which appears as a continuous barrier to the progress of the burr and deflects it from the dragging surface. The resulting bending effect on the burr, in its hot and relatively plastic state, when cut progressively from the workpiece, causes the thicker burr to also curl, although typically in a not-as-tight manner as the thinner burr of the lightest food. The ribbed effect of the composite harrow surface on the burr is produced in both thin and thick burrs, and promotes burst rupture sooner than would be the case with the continuous, uninterrupted end-to-end harrow surface of cut. The time required for a ribbed burr to reach the final stress of the material is less than for a non-ribbed burr, resulting in smaller burrs or turns of spar, ie fewer turns, than with a non-ribbed, non-ribbed burr.

For example, at a feed of 0.006"per revolution of the bore, the ribbed burr produced by the composite or" grained "harrow surface broke after one and one-half revolutions, typically, of its conical helix configuration, while produced by an identical insert in the other aspects, of the same size, operated at the same speed and feed, but without having "grains", typically produced a burst of more than three turns of conical propeller before breaking. produced by the insert of the invention are more easily cleaned out of the hole by the cutting liquid coming out of the tip of the drill, greatly reducing the incidence of clogging of the drill by the inability to break the burr for easy removal. preferred embodiment, illustrated as an essentially square block, is preferred for its robustness in the drilling context, as well as for the multiple cutting edges provided, since insofar as the insert is successively indexed around the axis of its central hole 22 to present each of the cutting edges in the active position of its predecessor, it wears to an unacceptable degree, usually reflected by the excess in energy consumption. However, it is also feasible to press the insert in the double-sided configuration by providing eight cutting edges in a square block insert, and where the center male 24, duplicated on the reverse side of the insert, becomes the seat surface of the insert in the alternating position that presents the identical cutting edges of the opposite face for cutting service. The free space of the heel behind the cutting edges of both faces, in such cases, requires an attitude of cleaning more forward of the active face of the insert, which to a certain extent can be compensated by a positive harrow angle more large of the peripheral harrow surfaces 16 on both sides of the insert. Those skilled in the art will recognize that the principles illustrated and explained are capable of adapting also to other polygonal shapes and other cutting applications. The aspects of the invention that are believed to be new and patentable are indicated in the following claims.

Claims (6)

1. cutting to said spine by a greater portion of the harrow surface and each providing there an upward inclined surface, remote from said cutting edge and ending in front of said spine, said spine moving up and back from said surface dredging so as to deflect a burst of stiffness sufficient to overcome said depressions, the height of said spine relative to said cutting edge being at least as great as the depth of said depressions relative to said spine.
2. The cutting insert of claim 1, wherein said loosening back and said harrow surface between said depressions are flattened.
3. The cutting insert of claim 1, wherein said depressions are spherical sectors and occupy approximately forty percent of said harrow surface.
4. 4. The insert of claim 2, wherein said depressions are spherical sectors of imaginary spheres that touch, of equal radius, and have a depth to said drag surface of approximately forty percent of said radius. The cutting insert of claims 1, 2, 3 or 4, having multiple indivisible cutting edges, wherein said smaller face is one of the multiple smaller flat surfaces of equal size and shape having the same relative angle to said first larger face so as to provide multiple identical cutting edges of equal width having peripheral harrow surfaces, depressions and identical ridges associated with them, said ridges forming the perimeter of a polygonal core central to said first larger face, said male having there a depression central to receive a fastener for attaching the insert to the body of a drill, said multiple cutting edges being indexable in series towards the cutting position by rotation of the insert on an axis through the center of said central depression perpendicular to said seating surface , one or more of said minor surfaces, when they do not serve as faces of free space, constituting surfaces of placement for the insert in the body of the drill. The insert of claim 5, wherein the cutting edges are four in number, in a substantially parallelepiped shaped block. SUMMARY The disclosed cutting insert (10) is a hard metal block configured on at least one of its larger faces (12, 18) to provide peripheral cutting edges (14) indexable successively around a location of a central fastener (21) to place each edge in series for cutting. The larger face slopes down and in from the cutting edges to provide positive harrow harrow surfaces (16) behind the cutting edges, and then rises like a sloping spine (34) to a central stall ( 24). A series of depressions (32) disposed along the drag surface produce a ribbed burst that breaks more easily, and in smaller burrs, easier to clean or otherwise remove from the cutting site.