This invention relates to a face milling cutter for the simultaneous rough and finish machining of a workpiece using identical inserts in the roughing and finishing stations of the cutter body, and to the on-edge cutting insert whose unique configuration makes it possible to index the same individual insert to present four different cutting edges for finish machining and four different edges for rough machining, to permit the same insert to be used for finishing and then for roughing, or vice versa.

BACKGROUND OF THE INVENTION While combination roughing and finishing face milling cutters, as such, are known, the indexable inserts employed in the roughing and finishing stations of the cutter body have been entirely different from one another, and typically employed at a ratio of one finishing insert to from four or six roughing inserts. The maintenance of the cutting efficiency of such cutters requires that two kinds of inserts be inven¬ toried, and in very different quantities of roughing and finishing inserts, in order to maintain the service¬ ability of the cutter. This presents problems of inventory control and cutter management in production machining, which is the objective of the cutter and insert of this invention to eliminate while at the same time doubling the service life of each individual insert in the same cutter body, independent of the direction of rotation of the cutter.

SUMMARY OF THE INVENTION The foregoing objective is attained by the invention in the provision of a face milling cutter body with alternately occurring stations, on the cutter periphery for roughing and on the face of the cutter for finishing, respectively, both stations employing iden¬ tical inserts, which are of generally parallelepiped form having specially configured, oppositely facing

cutting faces. When emplaced in a roughing station, the insert is positioned generally vertically, or nearly so, and the same or an identical insert when emplaced in a finishing station is approximately horizontal, which is to say that it sweeps in a plane perpendicular to the cutter axis as the cutter rotates. The inserts of the two kinds of cutting stations sweep paths which overlap in part, allowing the finishing insert to share a portion of the rough cutting load. The configuration of the cutting faces of the insert provides an edge-sharpening chip groove about the periphery of the cutting face, which is generally rectangular with radiussed corners, leaving a central land to serve the load transfer function when the insert is indexed to exchange cutting faces. The longer cutting edges of each cutting face are preferably ground with a mild arc to aid their finish milling function, as will become apparent. The net result is that each insert can be used eight times, four for roughing and four for finishing, without any intermediate grinding.

DESCRIPTION OF THE DRAWINGS The invention is described in detail below with reference to one embodiment that is illustrated in the drawings, in which: FIGURE 1 is a facial elevation of the milling cutter according to the invention;

FIGURE 2 is a side view of the milling cutter according to FIG. 1;

FIGURE 3 is an enlarged perspective represen- tation of an indexable insert that essentially is rectangular on all sides and can be arranged on the face as well as the outer circumferential surface of a surface milling cutter according to FIGS. 1 and 2;

FIGURE 4 is a section through the indexable insert according to FIG. 3 along the line IV-IV;

FIGURE 5 is a view in the direction of the arrow V in FIG. 3;

FIGURE 6 is a view of the indexable insert according to FIG. 3 in the direction of the arrow VI;

FIGURE 7 is a simplified schematic representa¬ tion of the arrangement of an indexable insert on the outer circumferential surface of the cutter body for roughing;

FIG. 8 is a simplified schematic representa¬ tion of the arrangement of an indexable insert on the face of the cutter body for finishing; and FIG. 9 is a schematic representation of the indexable inserts, in both stations, one for roughing according to FIG. 7 and one for finishing according to FIG. 8, on the cutter body of a surface milling cutter according to FIGS. 1 and 2, in which inserts of adjacent roughing and finishing stations are shifted into a common radial plane.

DETAILED DESCRIPTION OF THE INVENTION FIGS. 1 and 2 show a face milling cutter 1 in accordance with the invention. A number of cutting inserts in the form of an indexable insert 3 (FIG. 3) , are arranged on the periphery of the disk-shaped cutter body 2 and on the face 4 of the cutter body adjacent the periphery, such that they can be removed, exchanged, and/or transposed. The cutter body 2 is equipped with indexable inserts 3a at least within the circumferential region of its face 4. Each of these inserts 3a is oriented with its finishing edge essentially in a plane perpendicular to the rotational axis 5-5 of the milling cutter 1. The placement of the indexable inserts 3a on the face 4 of the cutter body 2 is such that their active cutting edges are able to remove metal radially as well as axially as the milling cutter 1 acts upon a workpiece. Each indexable insert 3a is accommodated in a pocket 6 arranged in the face 4 of the cutter body 2, as shown in FIG. 2. Each of these pockets 4 includes a

base seat 7, a rear seat 8, and a lateral seat 9. The relative arrangement of the base seat 7 and the longi¬ tudinal seat 8 of the pockets 6 is shown in FIG. 2. The relative arrangement of the rear seat 8 and the lateral seat 9 is shown in FIG. l.

The base seat of each pocket 5 in the face 4 of the cutter is inclined relative to the rotational plane 10-10 of the cutter face 4 being closer to the plane of the face in the advancing direction of rota- tion, with said incline defining the clearance angle of the indexable inserts 3a emplaced therein. The orientation and arrangement of the rear seat 8 and the lateral seat 9 relative to the base seat 7 is determined by the basic shape of the indexable inserts 3 used. FIG. 1 additionally shows that each indexable insert 3a is fixed in its pocket 6 on the face 4 of the cutter body 2 by means of a single retaining screw 11, preferably with countersink head that engages a counter¬ sunk hole centrally of said indexable insert, permitting the insert to be indexed or removed.

As the milling cutter 1 shown in FIGS. 1 and 2 is used as a face milling cutter for roughing as well as for finishing the residual workpiece surface left by roughing, the cutter body 2 is additionally equipped with indexable inserts 3b on its outer peripheral surface 12.

In contrast to the indexable inserts 3a arranged on the face 4 of the cutter carrier base 2, the indexable inserts 3b on the outer peripheral surface 12 of said cutter body are oriented essentially parallel to the rotational axis 5-5 of the cutter body, i.e., essentially vertically as shown in FIG. 2.

The indexable inserts 3b arranged on the outer periphery 12 of the cutter body 2 are uniformly distri- buted circumferentially, as are also the indexable inserts 3a on the face 4 of the cutter.

Each peripheral insert 3b also is mounted in a pocket 13 milled in the outer peripheral surface 12 of the cutter body 2, and defined by a base seat 14, a longitudinal rear seat 15 and an upper seat 16. In the pockets 13, the base seat 14 has a forwardly leaning inclination relative to the cutting direction, with said inclination defining the clearance angle behind the lower cutting, or "wiping", edge 31 (FIG. 3) of the indexable insert 3b. A prominent feature of the milling cutter 1 according to FIGS. 1 and 2 is the fact that the pockets 6 and 13 for accommodating the identical indexable inserts 3a and 3b are both disposed in the peripheral region of the cutter body 2, and are distributed uniformly and alternately on its face 4 and its outer peripheral surface 12. This means that each indexable insert 3b on the outer peripheral surface 12 of the cutter body occurs between two adjacent indexable inserts 3a on the face of said cutter carrier base 2, and vice versa. That is to say, one half of the cutting stations of the milling cutter 1 are arranged on the face 4 of the cutter body 2, with the other half of said cutting stations being arranged on the outer peripheral surface 12. This special arrangement is made possible by an insert of novel configuration which allows it to serve effectively either as insert 3a or 3b. Conse¬ quently, only one type of indexable insert 3 is required to service the cutter. One such indexable insert 3 is shown in FIGS. 3-6.

Each indexable insert 3 according to FIGS. 3-6 is essentially a rectangular parallelepiped in overall shape with two outwardly facing major lateral surfaces 21 and 22 that are parallel to one another, a bottom surface 23 and a top surface 24 that are also parallel to one another, as well as two outwardly facing,

parallel end surfaces 25 and 26, as shown in detail in FIGS. 4-6.

To adapt the insert for the sharing of the radial, rough-cutting load, the corners at which the respective lateral surfaces 21 and 22 converge with the end surfaces 25 and 26 of the insert 3, are rounded off at 27, as shown in FIGS. 3-6. A hole 28 that extends perpendicularly through the center of the lateral surfaces 21 and 22 is arranged in each indexable insert 3, and is countersunk at 29 to receive the previously mentioned countersink head retaining screws ll for fastening the indexable inserts 3 in their respective pockets.

The indexable inserts 3 shown in FIGS. 3-6 have a configuration such that each insert can be mounted on a milling cutter 1 of the type described in eight different positions before the cutting edges of said indexable insert must be resharpened, or the insert discarded. Each insert 3 in accordance with FIGS. 3-6 can be arranged on the face 4 of the cutter body 2 in four different installation positions as a finishing insert 3a, or arranged on the outer circumferential surface 12 of the cutter carrier base 2 in four different installation positions as a roughing insert 3b. Consequently, a milling cutter l according to

FIGS. 1 and 2, which is provided with indexable inserts 3 according to FIGS. 3-6, has a significantly increased service life and value.

The indexable inserts 3 according to FIGS. 3-6 have four long cutting edges 30, two of which extend along the longitudinal edges of the major surfaces 21, and the other two of which extend along the longitudinal edges of the opposite major surface 22. In this case, each of the long cutting edges 30 does not have an absolutely linear shape, but rather a slightly arcuate contour as shown in FIG. 3.

Four additional short cutting edges 31 of linear shape extend, respectively, along the two end surfaces 25 and 26, perpendicular to the cutting edges

30, and occur in pairs as the edges of the end surfaces 25 and 26.

In addition, each indexable insert 30 is eguipped with eight cutting edges 32 that extend in the shape of a quarter circle, with each of said cutting edges extending along a transition radius 27 from one of the lateral surfaces 21 or 22 to one of the end surfaces 25 and 26.

Two long cutting edges 30 with the arc-shaped contour and two short linear cutting edges 31, as well as the four connecting, rounded, corner cutting edges 32, frame the bottom surface 23 and the top surface 24 of the insert.

All of the cutting edges 30, 31, and 32 have positive rake angles, resulting from chip grooves 33 that are arranged in the bottom surface 23 and the top surface 24, inwardly of the cutting edges. Identical chip grooves 34 are also arranged in the bottom surface 23 and the top surface 24 along the end cutting edges

31. Within the region of the transition radii 27, the chip grooves 33 and 34 run together to ensure that the cutting edges 32 at this location, in the shape of a quarter circle, also have a positive rake angle.

FIG. 7 shows that the indexable inserts 3b are arranged on the outer circumferential surface 12 of the cutter body 2 to position circular cutting edge 32 either as the main roughing edge, or as the lower extremity of the main roughing edge, depending on the depth of cut. In either case, the adjacent short cutting edge 31 forms a secondary bottom cutting edge because the indexable insert 3b is mounted essentially vertically on the cutter body 2.

FIG. 8 shows a cutting edge 32 that is curved in the shape of a circular arc and acts as a

supplemental roughing edge on the indexable inserts 3a arranged on the face 4 of the cutter body 2, i.e., the finishing inserts that are essentially parallel to the rotational plane 10-10 of the milling cutter 1. In this case, a linear cutting edge 30 contiguous with the radially outermost circular cutting edge 32 is active on the workpiece surface, making a finishing cut.

As each indexable insert 3 according to FIGS. 3-6 provides four sets of cutting edges 30, 31, and 32 when installed as an indexable insert 3a according to FIGS. 1, 2, and 8, and four different sets of cutting edges 30, 31, 32 when installed as an indexable insert 3b according to FIGS. 1, 2, and 7, one can appreciate that each indexable insert 3 of the type shown in FIGS. 3-6 can be used in eight different installation positions on one and the same cutter body 2 without requiring resharpening, resulting in a distinct increase of the entire service life of the insert.

That is to say, irrespective of the direction of rotation of the cutter, each insert can be used in eight different indexes, four in the 3b peripheral roughing position and four in the 3a face or finishing position.

More specifically, in the 3b peripheral position, referring to FIG. 7, the lower right and the upper left corners of the cutting face presented in that view are interchangeable in that position to provide two roughing cutting edges. Moreover, if the active cutting face shown in FIG. 7 is interchanged with its rearwardly-facing opposite face, two additional diagonally opposite corners of the latter face are available for roughing, making a total of four.

That same insert remains available to present two pristine diagonally opposite cutting edges 32, 30 in the 3a position of FIG. 8, namely those which were the upper outermost and lower innermost in FIG. 7, and two

additional pristine edges of the same kind by turning the insert front for back in the FIG. 8 position.

Moreover, the symmetry of each cutting face 23 and 24 of the insert about mutually perpendicular axes, assures the availability of that versatility in either direction of rotation for which a given cutter body may be designed, making this cutter-insert combination particularly desirable for use in transfer line machining where opposite rotation of cutters for the simultaneous milling of surfaces on opposite sides of a workpiece are encountered.

The insert of the invention, being identical in its opposite cutting faces 23 and 24, is well adapted for opposed-plunger molding to form the somewhat intricate cutting faces 23 and 24, as well as the exterior shape, in the "green" carbide hard metal before sintering. After sintering, the insert may be chucked by its cutting faces for any form grinding of the major surfaces, end surfaces, and radiussed corners that may be desired, as well as for the arc-grinding of the linear cutting edges 30, earlier referred to.

The purpose of such arc-grinding of the linear edges 30 is to equip them to better serve their finish¬ ing function in the 3a insert position of FIG. 8. That is, when the insert in a 3a inclined pcoket is viewed head on, the convex curvature imparted to the cutting edge 30 by the arc-grind projects as a shallow ellipse when viewed from the front. The curvature is slight and not shown as such in FIG. 8 (but see FIGS. 3 and 5) and serves to feather the chip taken by finishing edge 30, as disclosed in U.S. Patent 3,762,005-Erkfritz for the advantageous purpose disclosed therein.

Not previously mentioned is the central, plane-surface land in the cutting faces 23 and 24, defined therein by the chip grooves 33 and 34. The plane land, of course, serves to transfer the cutting

loads from the insert in either the 3a or 3b position to the rear pocket surface.

FIG. 9 shows greatly magnified the detail of the milling cutter 1 which is encircled and identified by the reference symbol IX in FIG. 2. This drawing shows that the cutting edges 30 of the indexable finishing inserts 3a arranged on the face 4 of the cutter body 2 protrude axially slightly beyond the secondary cutting edges 31 of the indexable roughing insert 3b arranged on the outer peripheral surface 12 of the cutter body 2, e.g., by approximately 0.05 mm or 0.002 inches. However, this drawing also shows that the cutting edges 30 of the indexable inserts 3b arranged on the outer circumferential surface 12 of the cutter body 2 protrude radially slightly beyond the secondary cutting edges 31 of the indexable insert 3a arranged on the face 4 of the cutter carrier base 2, e.g., also by about 0.05 mm or 0.002 inches. It was established that this relative arrangement of these two groups of indexable inserts 3a and 3b on the cutter body 2 makes it possible to attain an optimal function of a milling cutter 1 that is utilized as a face milling cutter.

This relationship of the inserts in the 3a and 3b insert positions, respectively, automatically sets the depth of the finishing cut taken by insert 3a following after the roughing cut by the axially-oriented insert 3b. Moreover, in combination with the slight, radially outward offset of the peripheral insert 3b, the axial offset of the insert 3a permits it to share the roughing load along the lower portion of its rounded corner cutting edge 32 at all feed rates, and along progressively more of that edge 32 at moderate to heavy feed rates which increase the chip load per insert at the same cutting speed. It will be understood that the feeding direction of the cutter 1 is radial, with a slight forward tilt of the cutter rotational axis in the feeding direction to lift the cutting edges above the

finished surface on the trailing side of the rotating cutter.

The ability to use the same insert configur¬ ation for roughing and finishing by the same cutter, and to use the same individual insert in four orientations with four cutting edges both as a roughing and a finish¬ ing insert, greatly increases the cutting efficiency and the cost efficiency of the cutting operation, as well as eliminating the necessity of stocking multiple forms of cutting inserts, as the single insert of the invention form serves all stations of the cutter.

The features of the invention believed new and patentable are set forth in the claims.