Patent GB-168634-A (GB)
Title: Improvements in twist drill point grinding machines
IPC: B24B3/24
Filed: 1920-05-08
Abstract: 168,634. Hunt, H., Hunt, H. W., and Hunt, P., (trading as Hunt & Sons, H.). May 8, 1920. Addition to 122,735. Twist drills, sharpening.-The drill point is ground by a grinding-wheel A journaled in bearings on a tray 2 carried by a stand 1 and the drill is rotated, moved axially, and oscillated in an horizontal plane about a pivot 13, and is reciprocated parallel to the axis of the grinding-wheel. On the tray is mounted a slide 8 movable towards and from the grinding-wheel by a screw 12 carrying the pivot stud 13 on which is mounted a plate 14; the plate is supported also by a roller 15 carried by an extension 12<a> of the slide 12. On the plate is mounted a head 16 slidably carrying a tube 19, in which fits a hollow spindle 17 having thereon a drill-holding chuck 18. The tube 19 is screwed to receive a hand-wheel 22 and has a coned and slit end. The spindle 17 is adjustable axially within the tube 19 by a pin 23, and is secured in adjusted position by screwing-up the hand-wheel. The drill is rotated through a spur-wheel 28 on the tube 19 by a spurwheel 26 slidably keyed on a lay shaft 25, which is 'driven, through bevel-gears 27, 29, 31 carried by the plate 14, either by a handle 36, for adjustment, or through a bevel-wheel 37 and a clutch 40, 41 by a shaft 38 for grinding. The shaft 25 is slidable in the head and is rotatably connected to a plate 21 mounted on the tube 19. The shaft also carries a cam 43 engaging a pin 46 carried by the plate 14, rotation of the cam causing axial movement of the shaft, the plate 21, the tube 19, and the drill, there being two axial reciprocations in every revolution of the drill. The cam is pressed against the pin by springs 44 acting on plungers 45a carried by the plate 21. The plate 14 is oscillated about the pivot 13 by a link 48 connected eccentrically at one end to the bevel-wheel 31 and pivoted at the other end to a bracket 47 secured to the slide 12. The shaft 38 is driven, through bevelgearing and worm-gearing 50. 51 by the main shaft 49. In order to reciprocate the drill parallel to the axis of the grinding-wheel, the worm-wheel 51 has an eccentric block 55 thereon, which engages the grooved arm of the bell-crank lever 56, the other arm of the lever being connected by a link 57 to the slide 12. The slide may be adjusted relatively to the slide 8 by rotating a pinion 62 by means of a lever, the pinion being in engagement with a rack 60, to which the link is connected. The spindle 17 is set for correctly placing the drill by a latch 59 pivoted to the head 16 and adapted to engage a notch in the boss 20 of the plate 21. The drill is supported near the point by an interchangeable bush 24, as described in the parent Specification. In order to grind the flutes of the drill to maintain a uniform width of flute as the drill is ground down towards the shank, a thin grinding-disc is mounted on the outer end of the shaft 49 and the drill is supported in an adjustable inclined V-holder 75, Fig. 5, formed integral with a slide 74. The slide is movable on a bar 73, which is supported on the machine, by a handle 76, the flute moving in the plane of the grinding-disc. A plate is provided on the slide to engage the flute to position the drill.