Patent GB-1008097-A (GB)
Title: Attachment for use on grinding machines
IPC: B24B41/06
Filed: 1964-03-13
Abstract: 1,008,097. Grinding gun drills; drills. ELDORADO TOOL & MANUFACTURING CORPORATION. March 13, 1964 [March 13, 1963], No. 10629/64. Headings B3C and B3D. An attachment for use on a grinding machine for grinding tools such as gun drills comprises a protractor plate 29, Figs. 1 and 2, mounted for pivotal movement about an axis adjacent the edge of a base plate 12 adapted to be disposed parallel to the surface of a grinding wheel, means 22 for effecting angular adjustment of the plate about the axis, a workhead 46 mounted on the protractor plate for pivotal movement about a pivot 36 perpendicular to the pivotal axis of the plate, and means for selectively locking the work-head in angularly adjusted position, the work-head having means for releasably clamping a gun drill 116 in a spindle 84 for rotation and reciprocation relative to the workhead, and a plurality of cam means 174 interconnecting the workhead and spindle for effecting a selected distance of advance of the spindle during rotation thereof while pressure is exerted longitudinally of the spindle. The base plate is adapted to be secured by a key 22 to the table 12 of the grinding machine which includes a mechanism 16 for traversing the table past a grinding wheel. The protractor plate 29 is mounted on a pair of pivots 30 on lugs 24 upstanding from the base plate which has a recess 26 for receiving a sine gauge 27 engaged by a projection 32 depending from the protractor plate to determine the angle that the latter makes to horizontal and the clearance angle ground on the drill. The work-head is connected by the pivot 36 to the protractor plate which is formed with a segment 34 having a plurality of holes 40 selectively engageable by a detent ball 64, Fig. 3, carried by a lug 60 extending from the side of the work-head whereby the work-head is angularly adjustable relative to the pivot axis of the protractor plate. The work-head consists of a casting 48 having a liner 80, Fig. 2, which slidably receives the hollow spindle 84. The forward end of the spindle carries a master liner 96 retained in position by a set screw and having a radial projection 102, Fig. 6, extending inwardly. The liner is adapted to receive a bush 104 which has a bore 114 corresponding to the size of the gun drill to be ground and is slit to accommodate the projection 102, the bush being releasably retained in the liner by a screw 108 which also lightly clamps the drill so that it contacts the projection which extends through the slit. The near end of the spindle carries a hand wheel 88 and is formed with a threaded portion 180 carrying a micrometer nut 186 which has a cylindrical projection carrying a graduated dial 188 and a member 172 having a pin 196 extending into a longitudinal groove 198 in the spindle 84. The member 172 is formed with a plurality of steps forming cams 174 selectively engageable by a roller 156 carried by a screw 152 mounted in a bracket 146 secured to the casting 48; axial adjustment of the screw aligns the roller with a selected one of the cams to determine the axial movement of the spindle upon rotation thereof by means of the hand wheel 88 and the relief ground on the drill faces. The bracket 146 also has a recess 168, Fig. 3, for engagement by a pin 170 on the member 172 to position the cams at a zero position and in alignment with the liner at the front of the spindle 84. A plunger 158 is also carried by the bracket and can be moved to engage a recess in the cam member 172. The drill has a longitudinal notch 208, Fig. 12, and an oil passageway 206 and its end has a point 210 at the apex of an outer angle 212, which may be at 30 degrees to a line perpendicular to the axis of the drill, and an inner angle at 20 degrees to the line. A slight chamfer is also ground around the periphery of the drill from about 45 degrees below the outer cutting corner of the drill. In operation, the attachment is positioned relative to the grinding wheel of the machine by engagement of the point 130, Fig. 2, of a gauge 118 carried by the work-head with the surface of the wheel with the work-head set at its zero position on the protractor plate 29 and the desired sine gauge 27 in the recess 26. The gauge is then swung so that a projection 128 can be engaged by the drill tip to axially locate the drill in the lining 96, the rear end of the drill being supported by a bracket 138 on an extension 134. The work-head is then moved 20 degrees to one side of the zero position of the protractor plate and the spindle rotated by the handwheel 88 with the roller 156 engaging a selected cam to rotate and axially move the drill for grinding the inner angle 214, and is then moved 30 degrees to the other side of the zero position for grinding the outer angle 212, the depth of cut in each case being determined by rotation of the micrometer nut 184. Finally, the drill is removed from the attachment for grinding the chamfer on the edge of the drill.