Patent GB-945577-A (GB)
Title: Method and apparatus for grinding twist drills
IPC: B24B3/26
Filed: 1962-06-20
Abstract: 945,577. Sharpening twist drills. OLIVER INSTRUMENT CO. June 20, 1962 [June 27, 1961], No. 23785/62. Heading B3D. Apparatus for grinding twist drills comprises a support 11, Fig. 3, a rotatable sleeve 54 journalled on the support, an abrasive wheel 36, a wheel spindle 34 rotatable in the sleeve, the axis of the wheel being eccentric relative to that of the sleeve so that the wheel moves orbitally when the sleeve is rotated, a cam 104 for reciprocating the wheel in the direction of its axis, a drill chuck 230, means synchronized with the reciprocatory and orbital movements of the wheel for rotating the chuck to grind relief regions on the drill, adjusting means for the cam including a second rotatable shaft 318, gearing operated by the second shaft for adjusting the cam 104 and manual means 310 for advancing the rotating drill into engagement with the wheel. The belt-driven grinding wheel spindle 34 is freely rotatable within the sleeve 54, the sleeve itself being rotatable by a gear-wheel 72 through a reduction gear train driven by a pulley 40, Fig. 1. A second gear-wheel, 76, freely mounted on the sleeve 54 is driven by the gear train, 84, 86, 96 and may be coupled to the wheel 72 for driving the sleeve by a clutch mechanism, Fig. 6, comprising an axially movable pin 120 having a recess 128 engageable by a control member 155 operated by a hand wheel 136. A third gear-wheel 162 on the sleeve carries the face-cam 104 which is engaged by a rotary follower 118, Fig. 3, secured to the sleeve whereby it and the grinding wheel 36 are reciprocated axially; the phase relationship of the reciprocatory and orbital motions are adjustable through mechanism, whereby the cam 104 is rotatable by a handle about the sleeve 54 to vary the angular position of the cam faces relative to the sleeve; an indicator 184, Fig. 3, enables the adjustment to be observed through a glass panel 188 in the cover 48 of the wheel housing 46. The drill chuck 230 is rotatable in a fixed housing 236 secured to a swingable member 270 which is angularly adjustable about the axis of a vertical shaft 272 through which the drive to the drill is transmitted via bevel gear shafts 342, 378 and spur gear trains 72, 324, 328, 338, Fig. 3, and 404, 402, 406, Fig. 10. The housing 236 is secured in its angular setting by a T-headed bolt and eccentric clamping device 289, the forward end 414 of the chuck support member 270 being held in engagement with its pivot by a spring-loaded plunger 416. The chuck housing and pivoted support assembly as a whole are movable towards and away from the grinding wheel face for initial setting and feed in a direction parallel to the wheel axis by a hand wheel 310 which operates a screwed shaft rotatable in a nut 303, Fig. 3, fixed to a portion 278 of the machine frame, the driving bevel gear 362 being slidably keyed on the shaft 342 and journalled in a bearing block 370 secured to the movable member 276 on which the chuck support 270 is mounted. Means for rotating the chuck 230 at three different speeds relative to the grinding wheel to accommodate drills having two, three or four flutes comprises three spur gears 324, 328, 326, Fig. 3, which are selectively engageable, through a lever 450, Fig. 1, by a cluster of gears 334, 338 and 336 slidably mounted on and keyed to a sleeve 332 secured to the shaft 342. Coolant is supplied during grinding by a tube 466 and nozzle within the wheel shroud 464, and is collected in a tray portion 558. Also carried by the shroud is a wheel dressing device, Fig. 9, comprising a manually operated lever 474 and swinging member 476 which carries a dressing tool 480 and a drill gauge plate 482 having an angular edge against which the tip of the drill is brought into contact when positioning the drill preparatory to grinding. Dressing is effected before engaging the clutch coupling the spur wheels 72 and 76.