Patent GB-565119-A (GB)
Title: Method of shave-milling steel and cutters therefor
IPC: B23C5/24
Filed: 1942-12-17
Abstract: 565,119. Millig-cutters. O.K. TOOL CO.; Inc. Dec. 17, 1942, Nos. 17966 and 17967. Convention dates, April 25, 1942, and May 7, 1942. [Class 83 (iii)] A milling-cutter, particularly for milling steel, has carbide tipped cutting-blades which are arranged so that the end cutting-edges come progressively into action from inner to outer portions of the edges while the parts of the peripheral edges located away from the end face come into action before the edges adjacent the end face. By this setting the chip-engaging face of each blade leans forward and overlies the chip in both radial and axial directions. The cutter element 10 seen in an axial view in Fig. 1 is inclined forwardly at the angle a so that the outer corner f of the end cutting-edge j trails more inwardly located points on the edge. Thus in taking a cut with this edge, Fig. 7, a point spaced from the corner of the blade is the first to strike the work at point e. The blades are also given a second tilt at an angle b, Fig. 3, so that a peripheral edge g is helically disposed with respect to the cutter axis, the hand of the helix being so disposed in relation to the direction of rotation that the corner e of the work is first engaged by a point on the peripheral edge spaced from the end face of the cutter. In this way the shock normally produced when the corner of the cutter strikes-the work is borne by wellsupported parts of the blades: The position of both the end edge and peripheral edge g is shown in Fig. 2. The extreme point f may in some cases be bevelled off. In practice the peripheral cutting-edge y is helically arranged (angle b), the direction of the helix being such that the end point f is circumferentially behind points spaced axially inwards from the point f. Since the cuts of both peripheral and end edges are started away from the point f and proceed towards such point, the chips are in effect pushed away from the cutter and do not build up on the edges or cause clogging and a mirror finish is produced on the work. In one example, a 6 inch diameter cutter may be driven at 247 r.p.m. with a feed of 5# inches per minute. Fig. 10 shows a face and side milling- cutter with blade slots 13 receiving blades having tungsten carbide tips 20. The slot wall 15 which locates the cutting edge has a helical inclination of 10 degrees. The slot wall is also inclined at 10 degrees to a diametral plane so as to give the required lean to the end cutting- edge 25, Fig. 14. These angles may be varied. Preferably, part of the edge is in front of and part is behind a diametral plane so that the tool exerts a downward pressure on the work piece. The cutting-edges have a wider cutting- angle than the normal, since the tilt of the blade, Fig. 12, provides clearance of the same angle as the tilt if the cutting-angle is 90 degrees. In some cases this cutting-angle may be exceeded. In addition to the relief for the cutting-edges (shown in dotted lines in Fig. 14), the parts of the blade outside the carbide tip 20 have a relief of 1-2 degrees on the side edges and 5 degrees. on the end edges so as to prevent these parts from dragging on the work. The clamping of the blades may be effected by wedges, screws, &c. As shown, the blades have longitudinal taper and the rear surface is serrated at 30, the blades being inserted from the face of the cutter and tapped into position. The blades may be stepped outwardly to compensate for wear. The invention is applicable to face cutters and peripheral cutters or to slotting cutters which cut on both faces.