Patent GB-720976-A (GB)
Title: Improvements in or relating to devices for sharpening twist drills
IPC: B24B3/24
Filed: 1953-05-28
Abstract: 720,976. Sharpening twist drills. GUHRING, O., GUHRING, A., and GUHRING, M., [trading as GUHRING, G.]. May 28, 1953 [May 28, 1952], No. 14896/53. Class 60 A device for sharpening twist drills, comprising a drill-holding fixture adapted to swivel about an axis inclined and adjustable in relation to the grinding wheel, is characterized in that the drillholding fixture comprises two parts, one of the parts being slidable transversely to the drill axis, the other part being slidable in a direction parallel with the grinding wheel face. The grinding wheel 3 is carried by a shaft 2 supported in the frame 1. A carriage 4, adjustable as to height, and a laterally adjustable cross slide rest 4<SP>1</SP> are supported on the frame below the grinding wheel. A pivot 5 on the part 4' supports a member 6 on which is mounted a swivelling shaft 7 carrying pivotally an arm 8; by means of an adjusting screw 10, the axis of the shaft 7 can be set to the correct angle relative to the grinding wheel face. At the upper end of the arm 8 is a transverse beam 11 provided with a handle 12 for swivelling the arm 8 about the shaft 7. The end of the beam 11 nearest the grinding wheel carries a holder 14 adjustable, by screw 14a, in a direction parallel wi the grinding wheel face in a pin and slot guide, 13, 13a. The lower end of the holder carries a post 15 serving as a support for the front end of the drill, and a calibrated adjusting pin 15a is provided to enable setting of the device at the proper distance from the grinding wheel to be effected by means of the shiftable cross slide rest 4'. A member 18, provided with a pin 17 having flattened sides, is slidably mounted in a longitudinal slot 16 in the beam 11. The pin 17 constitutes a guide for a holder 19 which is adjustable, by a screw 19a, perpendicularly to the beam and which carries an adjusting spindle 20 which has a conical recess on one end to form a seat in which the end of the drill is inserted. To permit rapid setting of the device to the correct spacing x of the point of intersection of the axis of the shaft 7 with the axis of the drill for various diameters of drills, the holders 14, 19 are provided with calibrated scales 14b, 19b co-operating with fixed marks on the beam 11 and member 18 respectively. Because of the relative inclined positions of the holders 14, 19 the graduations of the scales are so inter-related that the correct setting is obtained by adjusting the two scales so that the same numeral on each scale registers with the fixed marks, this numeral indicating the diameter of the drill. To ensure that the lips of the drill are approximately vertical when entering into contact with the grinding wheel, a two-armed lever 22 is pivotally supported by a pin 21 on the beam 11, the shorter arm of the lever rotatably supporting a wheel 23 provided on,its periphery with pins 24 of gradually decreasing diameters. The pins are adapted to engage, under the effect of a spring, one of the spiral flutes of the drill; the indexing pin is retracted from the flute by depressing the longer arm of the lever 22 and inserted in the other flute after the drill has been rotated through 180 degrees. To secure the desired relief angle, the arm 8 is shifted on its hub part 8a longitudinally in a guideway 25.