Patent GB-840517-A (GB)
Title: Apparatus for grinding or sharpening rock drills, bits or like tools
Inventor: GREA JAMES WALLACE STEVEWELL M
IPC: B24B3/33
Filed: 1957-10-22
Abstract: 840,517. Grinding drills. HALIFAX TOOL CO. Ltd. Jan. 22, 1959 [Oct. 22, 1957], No. 32927/57. Class 60. An apparatus for grinding a rock drill or like tool generally of the kind shown in Fig. 9, having outwardlyextending V-shaped ridges 4 ground obliquely along lateral faces 5 to provide cutting edges 6 comprises a grinding wheel 16, Fig. 4, relativelymovable table 24, which has drill-holding means 30 for presenting the drill to the grinding wheel with its axis disposed in one or the other of two angularly-disposed alternative positions enabling one or the other of two opposite lateral surfaces 5 of a ridge to be ground, and means permitting indexing or adjustment of the drill about its axis in the holding means for the grinding of the lateral surfaces 5 to be performed successively. The table 24 is reciprocated in guides 23 in the machine shown in Fig. 4, and carries a turntable 30 which constitutes the drill-holding means and carries the actual drill holder 29. The grinding wheel 16, Fig. 1, is belt-driven by a motor 13, both the grinding wheel and motor being carried on a beam 12 pivoted on a pillar 13. The shank of the drill is inserted in the holder 29 in a sleeve 42 and may be adjusted axially by a screw 43, before the sleeve is secured by a clamp 40. The drill is held against rotation within the sleeve during grinding by a fork 44, Fig. 1, which is spring- loaded to engage an arm of the bit, and is carried by a plate 48 angularly adjustable about the axis of the bit to enable the latter to be set in correct position in relation to the grinding wheel for the grinding of the faces 5 or relief surfaces 7, Fig. 9. The turntable 30, which has graduations 35, is adjustable between the limits of an arcuate slot to provide a 90 degrees swing for the normal four-armed drill of Fig. 9, but it may be secured by a clamping bolt in intermediate position for drills having smaller angles between cutting edges. The worktable 24 is operated during grinding by a hand-wheel 27, Fig. 1, so as to traverse the face of the drill across the periphery of the grinding wheel, and adjustment of grinding pressure is obtained by a hand-operated screw-threaded shaft 17, having a spring 22 located on one side or the other of the beam 12. With the turntable 30 in one extreme position, the lateral faces 5 on one side of the four cutting edges 6 are successively ground, the drill being indexed through 90 degrees in its holder after each grinding operation ; the relief surfaces 7 on the same lateral faces are then similarly successively ground after appropriate adjustment of the plate 48. The other four lateral faces 5 and relief surfaces 7 are then similarly ground with the turntable in its other extreme position. Alternatively, the turntable may be swung from one position to the other between the grinding of successive cutting edges. After all the surfaces 5, 7 have been ground, the drill and sleeve 42 are removed from the holder 29 and placed in another holder 57, Fig. 4, which positions the drill for peripheral relief grinding. In the modification shown in Fig. 12, the turntable 30 and single holder 29 are replaced by two fixed supports 291 spaced apart at the requisite angle on a slidable base 241 movable by a lever 73. A drill-holding sleeve is clamped in the respective holder by a bar 76, the sleeve being provided with a square projection at its lower end to engage with a square recess 79 at the base of each support to locate the drill for grinding successively the inclined faces 5 of the four cutting edges. A clamping screw secures the drill within the sleeve and may be used to hold it at intermediate angular positions for relief grinding. Fig. 17 shows a fixture for use with this embodiment for peripheral grinding which allows the angle of inclination of the axis of the bit to the grinding wheel axis to be adjusted by means of a bolt 102 securing the sleeve-holding socket 100 within the limits of a slotted hole in the base of the socket. The drill is rotated by a hand-wheel 108 and is movable axially by a lever-operated rack and pinion. The beam 12<SP>1</SP>, Fig. 13, supporting the grinding wheel is also movable in the direction of the wheel axis in this embodiment by means of a handwheel 92 and a screw-and-nut arrangement. The motor 13 is carried on a downward extension 81 of the beam 121, the extension abutting against the head of a pressure-regulating screw 82 engaging a spring-pressed bush 83 slidable within a tube 84 ; the bush 83 may be locked in position by a set screw 90 to hold the beam and the grinding wheel unyieldingly against the bit during peripheral grinding. Liquid may be supplied by a jet to the grinding wheel. A grinding wheel truing device may also be incorporated in the apparatus.