GB875566A - Improvements in or relating to grinding apparatus - Google Patents

Abstract

875,566. Grinding tools. CATT, F. A., and CATT, J. A. April 3, 1959 [Jan. 3, 1958; June 24, 1958; Oct. 20, 1958], Nos. 340/58, 20274/58 and 33486/58. Class 60. Apparatus for grinding tools comprises a structure 115, Figs. 1 and 2, mounted for movement in a direction substantially parallel to the axis of a grinding wheel 112, a carrier 123 mounted on the structure to swing about an axis parallel to and spaced from such axis, and a tool table 125 pivoted on the carrier for movement about an axis at right angles to the axis of the grinding wheel ; the carrier is extensible radially from its axis of swing to permit variation of the radius of the arcuate path of swing of the table, such path being movable to and from the grinding wheel by reason of the mounting of the structure. The grinding wheel is mounted on the shaft of a motor 111 on a base from which two pairs of spring blades 114 arranged in X-formation depend for the support of two double-cranked members 115. Radius arms 119 carried by a tube 118 rotatable in the members 115 support a tube 120 providing a pivotal bearing for a shaft 121 which at its outer end has aT-socket 122 receiving the shank 123a of the carrier 123. The upper yoke part 123b of the carrier provides a pivotal mounting for the table 125 and a tool rest 126 is pivoted on the upper face of the latter. The position of the carrier 123 is adjustable in the socket 122 and also by varying the position of the tube 120 by means either of a cable 131 or a linkage associated with a ratchet and detent. A bracket 138 projecting from the shaft 121 co-operates with stops 137 to limit the arc of swing of the carrier with the shaft. The inclination of the table 125 about its pivotal mounting is adjustable by a screw 129 and is indicated by a pointer 135 connected by a cable 134 with the table and movable over a scale 136. In the modification shown in Fig. 1 of the second Provisional Specification, the shaft 24 providing the pivotal axis of the carrier is mounted in a tube 22 carried directly by X-shaped springs 15. The shank 54 of the yoke-shaped carrier 56 is secured to a member 40 which is adjustable vertically by a lever 45 on a tubular member 34 arranged to be clamped in desired position in a T-socket 26 at the end of the shaft 24. The tool table 60 is pivoted by screws 57 in the yoke 56 and tiltable by a screw 61, the degree of tilt being indicated by a pointer 79 which is operated by either a cable 67, rack-and-pinion gearing with or without a cable, or an hydraulic drive. The table is fitted with a tool holder 104 and a pivoted tool rest 82 which can be set in desired position by adjustable stops on the periphery of the table. The tubular member 34 is provided with a cam follower 109 for cooperating with a cam track 110 in order to grind a desired profile on the tool ; in this case, the grinding wheel has a narrow annular rib for tracing out the shape of the cam on the tool. An alternative form of grinding wheel consists of an aluminium back plate 98, Fig. 4 (second Provisional Specification), with three nested annular grinding discs 100, 101, 102, of which the intermediate disc has the coarsest grain ; the discs 100, 101 are bonded to the plate 98 and the disc 102 only to the other discs. If desired, the X-shaped rings 15 may be omitted and the shaft is then merely mounted for rotation and axial movement in a fixed frame. A tool rest and holder suitable for grinding twist drills may be provided with means for engaging a flute of the drill in the required angular position, grinding being effected by swinging the carrier to bring the drill tip into contact with the inner cylindrical face of an annular grinding wheel. The apparatus shown in Fig. 1, may be utilized for sharpening boring tools so that correct clearance angles in accordance with the diameter to be bored are formed by the provision of a gauging device in the form of a bracket 139 rotatably mounting a snail cam 140 which is marked off around its periphery for different bore sizes. The cam having been set for the desired bore, a depth gauge is inserted between the top of the cam and a stop at the top of the bracket and then transferred to a position at the top 141 of the wheel guard ; the complete carrier structure is then adjusted to bring the top face of the tool in the tool carrier into contact with the lower edge of the gauge. In order to clean the grinding wheel, its back plate is provided with scoops for raising paraffin from a bath to a baffle provided with a gutter for discharging the paraffin on to the inner face of the wheel ; the paraffin is collected by a gutter surrounding the tool table, and pumped back to the bath. Alternatively, a felt pad fed by a wick from a bottle of paraffin can be brought into contact with the grinding wheel at intervals. The grinding wheel may be dressed by a diamond on the end of a lever which is pivoted to swing across the face of the grinding wheel. The first Provisional Specification describes also the grinding wheel as being formed of two nested portions of different grain sizes bonded on one side of a backing plate or of two wheels of different grain sizes which are either secured on opposite sides of a disc of soft material or moulded together.