Patent GB-997245-A (GB)
Title: An improved method for grinding drills and apparatus therefore
IPC: B24B3/24
Filed: 1963-01-21
Abstract: 997,245. Grinding. T. GROB, and D. H. TESKER. Jan. 21, 1963, No. 2540/63. Heading B3D. A method for grinding a drill point comprises the steps of rotating a grindwheel 11, Fig. 1, having a truncated conical peripheral configuration, oscillating the grinding-wheel on an axis 62 substantially parallel to the axis 63 of the grinding-wheel to generate a segment of a hollow cone having its apex on the axis of oscillation, and feeding a drill into the peripheral surface of the wheel to grind a portion of a conical surface on the point of the drill. The grinding-wheel and its motor 21 are adjustable by a hand wheel 32 and screw 31 along guides in a frame member 20 which is oscillatable by a crank 24, 25 driven by a motor 22 about pins 18 in a support 16. The grinding-wheel is adjustable by the hand wheel 32 to a position in which its surface is shaped with the conical configuration by a dressing tool 33 mounted on a shaft 58 axially movable by a hand wheel 60. The support 16 is mounted on a plate 13 adjacent a base 34 for a drill support which has a plate 36 movable along guideways 35 on the base by a screw 37. The plate 36 has a concave upper surface receiving an angularly-adjustable member 36<SP>1</SP>, Figs. 4 and 6, having a pair of blocks 40 formed with V-shaped notches 46 for supporting a drill 12; the member 36<SP>1</SP> is adjustable on the plate 36 about an axis through the apexes of the notches 46 in accordance with the desired relief angle to be ground on the drill. The notches are 7 degrees offset from the vertical to compensate for the different web thicknesses of differently sized drills. A drill to be sharpened is positioned in the V-notches with one of its cutting edges vertical and a parallel-sided dog 52 is clamped to the drill with one of its parallel sides abutting a pin 57 and its front face abutting the end of the member 36<SP>1</SP>. The drill is advanced towards the rotating and oscillating grinding-wheel by the hand wheel 38 to grind one of its lands, the reading on a micrometer 39 being noted before the plate 36 is retracted Thereafter the drill is rotated 180 degrees to bring the other side of the dog in contact with the pin and the plate 36 advanced to the same reading on the micrometer to grind the other land. In another embodiment, the drill 90, Fig. 18, is supported in V-shaped notches in blocks 70 adjustably mounted on a plate 71 secured to a block 81 adjustable in curved guides 84 to the desired relief angle to be ground. The drill is located during grinding by projections 96 which abut a pin 74 and are mounted on a ring clampable by a nut 94 against a shoulder on a member 91 having an internal taper corresponding to that on the shank 92 of the drill. A second abutment pin may be provided adjustably spaced from the pin 74 whereby when the drill is rocked to a position wherein the projection 96 abuts the second pin, the drill is ground with a centre point. In the second embodiment, the conical configuration is produced on the grinding-wheel by a dressing tool mounted on an arm 101 which is rockable about a pivot by rotating a hand wheel.