Patent GB-1506543-A (GB)
Title: Machine for machining spiral cutting edges on cutting tools
IPC: B24B3/00
Filed: 1976-06-07
Abstract: 1506543 Grinding cutters; milling R HABIB 7 June 1976 [6 June 1975] 23383/76 Headings B3D and B3K A machine for grinding or milling a spiral cutting edge on a workpiece 20 having an elongate shank with an at least partially rounded head by relatively moving the workpiece and a rotating tool 19, comprises a support unit having a first support 2 and a second support 6 mounted for sliding movement relative to one another in a horizontal plane and rotation about a vertical axis 60, a headstock 4 having a workpiece carrying spindle 5 carried by the first support and being positionable so that the axis of the spindle intersects the vertical axis, a device 12 mounted on the second support for helically driving the spindle, means for mounting the support unit and tool for vertical translational movement relative to one another, and means for simultaneously imparting a relative vertical translatory movement to the support unit and tool and a rotation of the support unit about a vertical axis to provide a helicoidal relative movement of the support unit and tool. A longitudinal slide 1a is slidably mounted on a piece 1b which is fixed to the frame of the machine and through which is slidably mounted a transverse slide 1c earrying a column mounting a carrier for a grinding wheel as described in Specification 1,325,650. The headstock 4 is mounted by way of an intermediate piece 65 on the first support in the form of a table 2 and is adjustable transversely of the axis of the spindle 5 by pins 70, 71 and knurled nuts 63, 64. The table 2 is slidably mounted by needle bearings on the second support 6 which has a box-like part 9 carrying a device 12 for helicoidally driving the spindle 5, the device being as described in the above-mentioned Specification of of the sine-bus type. The support unit comprising the table 2 and support 6 is mounted on a third support consisting of a column 14 which is secured to abase 17 fixed to the longitudinal slide and engages a sleeve 52 in the support 6 by way of a ball race 54 whereby the support is axially and rotatably movable on the column. The third support also includes a plate 15 which is adjustable, by rotation of a cams 38, 39 fixed to a shaft mounted in the plate and rotated by knobs 40, 41, about a pivot 16 on the base 17, the plate having an arcuate track 27 engaged by a roller 21 mounted in bearings 49 on the part 9 of the support the inclination of the plate is adjusted by the cams so that as the support is moved about the axis of the column, the track imparts movement to the support along the axis of the column. The movement of the support about the column is limited by engagement of the bearings 49 with adjustable stops 47, 48 and an adjustable rod 25 engaging a limit switch 50. The movement of the table 2 on the support 6 is limited by engagement of abutments 29 adjustable along a groove 28 with a fixed stop 30 on the support. Each abutment also carries an adjustable rod 33 for actuating an end of path switch 36, 37. The upper end of the column 14 has an extension 55 on which is mounted an arm carrying a micrometer 58 for use in adjusting the position of the cutter to be ground. In operation, the end of the workpiece is initially brought into alignment with the axis 60 of the column by movement of slide la, the micrometer then being adjusted to the radius of the hemispherical end 20a and the workpiece advanced to position 20<SP>1</SP> so that the axis 60 passes through the centre of the end. Adjustment of the nuts 63, 64 effects a slight transverse adjustment of the headstock 4 which is a function of the diameter of the workpiece and the pitch of the helix 20b. Cams 38, 39 are actuated to adjust the plate 15 an amount corresponding to the difference in height at the end 61 of the hemisphere and the point 62 where the helix along the cylindrical part of the tool begins. A jack acting on an arm 51 moves the support about the column 14 wherein the roller 21 abuts stop 47 and wherein the grinding wheel contacts point 61 of the workpiece. As the roller runs down the track, the support moves around the column at a speed determined by braking by the jack and the support unit describes a helix, the slope of which is zero at the starting position 61 and progressively increases (20c) to the point 20b at which switch 48 actuates the helical drive device of the spindle 5. The grinding wheel may be adjusted to grind the cutting edge or to back-off the cutting edge. In another embodiment, a screw or helical ramp of constant slope replaces the inclined plate 15, and the spindle 5 may be advanced by a jack driving a sliding carriage having a roller fixed to a toothed belt driving a pinion which rotates the spindle. In a further embodiment the third support consists of a vertical column having a helicoidal shoulder or groove co-operating with a helicoidal shoulder or rib on the first support.