Patent GB-921630-A (GB)
Title: Twist drill grinder
IPC: B24B3/24
Filed: 1961-09-15
Abstract: 921,630. Grinding twist drills. HAMMOND MACHINERY BUILDERS Inc. Sept. 15, 1961 [Nov. 14, 1960], No. 33245/61. Class 60. A twist drill grinder comprises a driller-holder 89 mounted for arcuate movement about a first axis to adjust the point angle to be ground by a wheel 4, the holder also being capable of pivotal movement about a second axis transverse to the first to move a lip of the drill across the grinding surface in a support which is pivotally movable about a third axis, parallel to but offset from the second axis to adjust the relief angle to be ground, the support also being movable towards and away from the wheel. The drillholding unit is supported by a sector 9 whose rotational centre, forming the first axis, is intersected by the axis of a shaft 46, Fig. 4, the axis of the drill passing below the shaft axis by an amount determined by the amount of relief required. The sector 9 is carried in a housing 8 secured by a fixed pivot screw 63 (the third axis) and a bolt 74 to a swing-plate 48 rotatable with the shaft 46 which is itself journalled in a housing 7 having a base 37 bolted to a platform 6 pivotally attached to the base 1 of the grinder. An adjustable counterweight 106 enables the sector housing 8, sector 9 and carrier unit 11 to swing freely with the shaft 46. A lip-rest having a locating finger 105 is adjustably held by a clamp 102 in a groove formed on the outer surface of the housing 8. The holder 89 is manually movable on rods 87, 88 and is secured thereto by a clamp 92, the tailstock 91 being similarly adjustable by a clamp 93; a micrometer unit 90 determines the support point for the drill shank and effects feed during grinding. An adjustable ring 51 surrounding the housing 7 of the shaft 46 has a projection 53 which extends forwardly into a gap between stops 57, 58 formed on the periphery of a second ring 54, mounted on the housing 7 adjacent the ring 51. A set-screw 56, Fig. 2, secures the ring 54 against rotation after initial adjustment and a thumb-screw 55 clamps the ring 51 to the housing 7 at the required setting of the stop 53 between the stops 57 and 58, whereby the rotation of the drill holder about the axis of the shaft 46 is determined, the extent depending upon the number of lips on the drill. Angular adjustment of the sector 9 on its housing 8 is effected by a clamping screw 86, aperture 83 being provided opposite a scale on the sector so that the holder may be adjusted to the required point angle. The relief adjustment is effected by shifting the sector housing 8 about the pivot screw 63 by an eccentrically bored bush 67 carried by the swing plate 48. Rotation of the bush by a handle 77 causes the point of the drill to move in a direction substantially perpendicular to the plane of the housing 8 and to the axis of the shaft 46. The flange 68 of the bush 67 is preferably provided with a scale showing relief angles. The entire assembly is movable towards and away from the grinding wheel by a crank-handle 18 which rotates the screwed shaft 17, forming a fourth axis and a pivot for the platform 6, Fig. 7, which is itself adjustable vertically by a screw 25, this axis being parallel to the grinding wheel axis. A spring 34 inserted between the base 1 and the underside of a pivotal member 30 in contact with the screw 25 urges the platform 6 upwardly but to an inactive position; downward movement of the assembly, as by a treadle T and link L, Fig. 2, brings the work into grinding contact with the wheel 4. The drill may be clamped or held manually against its support during grinding.