GB299640A - Improvements in drill grinding machine - Google Patents

Abstract

299,640. Jackson, T. A., and Skelly, W. J. Dec. 23, 1927. Twist drills, sharpening; guides and rests. - In a machine for grinding twist drills, the drill is mounted in fixed axial relation to a rotary grinding-wheel mounted in a head having a planetary movement around the drill which is fed axially towards the head. The cylindrical bed portion 11 carries a sliding sleeve 12 provided with a vertical post 16 to which is adjustably clamped a chuck sleeve having a channelled extension 20. A slotted cam plate 22 sliding on the portion 20 is provided with a lug 24 connected by a link 25 to a pivoted lever 26 moving over a toothed quadrant 30. The slots in the cam plate are engaged by blocks 36 carried on the chuck members 32 which slide between guides 31 and which have jaws to grip the drill 35 to be ground. The jaws are thus closed to grip the work by means of the lever 26 and the clamping pressure may be further regulated by an eccentric 37 acting on the link 25. The grinding-head is operated from a shaft 40 which is connected through spur gearing 43, bevel-gearing 45, and worm gearing 48, to a low-speed sleeve 50 which terminates in a yoke 51 and imparts the planetary movement to the grinding wheel 70. A two-part shaft 53 passes through the parallel arms 52 of the yoke into a rocking block 55 which is provided with an arm 72 accommodating the upper end of the grinding-spindle. The latter is driven from the shaft 40 through friction bevel gearing 81, friction gears 84, 85, 62, spur gears 61, 63 and bevel gearing 67. The arm 72 is adjustably connected to an arm 77 carrying a roller running on a stationary cam 74. In operation, for grinding a two-lip drill, the cam is provided with two raised portions 75 so that the arm 77 is lifted to rock the grinding wheel towards the drill axis twice during a revolution of the grinder head to give the proper clearance to the cutting edges. The cam 74 may be composed of two parts connected as shown in Fig. 10. The point of the drill is supported opposite the grinding-wheel by an arm 86 adjustably secured to the yoke arm 52. Axial feed of the drill is effected from a cam 96 mounted on the sleeve 50 and coacting with a block 98 on a bolt 101 connected to a pawl 104 coacting with a ratchet wheel 113 which is connected by gearing 114 to a feed screw 117. An adjustable shield plate 105 serves to control the amount of feed imparted at each stroke by the pawl 104. On completion of the operation the feed screw may be rotated from a hand wheel 120 to withdraw the drill.