GB1103427A - An apparatus for grinding drills - Google Patents

Abstract

1,103,427. Grinding. A. E. AHLSTROM. 10 June, 1965 [4 March, 1965], No. 24524/65. Heading B3D. Apparatus for sharpening a twist drill while the drill is held in a chuck on the spindle of a drilling machine, the apparatus being held manually during the grinding operation, comprises means for driving a grinding disc 16 from the rotating drill, the shaft 17 of the grinding disc being adapted to be swung from a position, in which an edge of the drill is ground, in a lateral direction in a plane perpendicular to a plane containing the axis of the drill, and a coupling which, when the grinding disc is swung away from the drill, permits the drill to rotate in relation to a rotor 7 carrying the grinding disc a part of a revolution corresponding to the number of cutting edges on the drill, the disc then being swung back to its initial position to grind the next cutting edge. The rotor 7 is supported at its lower end by a pivot 8 engaging a bearing 9 in a casing 6 which, at its upper end rotatably supports a sleeve 12 of the rotor, the sleeve rotatably receiving a chuck 13 for engaging the drill. A stand 20 is journalled in the lower portion of the rotor and is provided with a pair of trunnions 19 carrying a housing 18 for the shaft 17 of the grinding disc 16, the shaft being connected by bevel gears 21, 22 to a shaft 23 having a gear 24 engaging a gear 25 fixed to the casing 6. The housing 18 is urged about the trunnions 19 in a direction to engage the grinding disc with the drill by a spring 28, the upward movement being controlled by a pin 29 secured to the housing engaging a cam 31 on the rotor whereby the clearance formed on the drill is controlled during swinging of the stand 20 in its journal. The swinging of the stand is effected by a pin 34 which engages a cam track 35 on the lower side of a cam disc 36 and is secured to the end of an arm 33 mounted on a pivot 43 on disc-shaped portion 42 of the rotor 7. The cam track and a gear 37 to which it is secured are rotatably supported on the sleeve 12, the gear 37 meshing with a small gear 39 which also meshes with a gear 38 secured to the sleeve 12; the gears 37, 38 have the same diameter but differing numbers of teeth so that as the rotor rotates in the casing, the cam disc 36 rotates relative to the rotor to cause the swinging of the stand 20 and hence the grinding disc. The pivot 43 also carries an arm 44 having an end 45, Fig. 10,. for engaging a flute of the drill during grinding, the arm being movable by a driver 46 on an arm 47 secured to the pivot 43, the arm 47 also acting to support the drill during the movement of the drill to present a fresh cutting edge to the grinding-wheel. The rotary movement of the drill relative to rotor to present the cutting edges to the grinding position is permitted when a lobe 57, Fig. 15, on a cam track 56 on the cam disc 36 rocks a lever 52 mounted on a pivot 48 on the sleeve 12 from a position abutting a projection 54 on a flange-shaped portion 55 of the sleeve 13. The portion 55 has two or more projections according to the number of cutting edges on the drill for successive engagement by the lever 52 to couple the rotor to the drill for the successive grinding of the cutting edges, the lever being urged into a position for abutting the projections by a spring 50 after passage of the lobe 57. A fan 59 secured to the grinding disc blows chippings through openings 5 in the casing 6.