GB771967A - Improvements in or relating to devices for sharpening twist drills - Google Patents

Abstract

771,967. Sharpening twist drills. GUHRING. O., GUHRING, A., and GUHRING, M., [trading as GUHRING, G.]. Aug. 5, 1954 [Aug. 25, 1953], No. 22834/54. Addition to 720,976. Class 60 In apparatus for grinding twist drills as in the parent Specification, the pin 7, Fig. 1, about which the drill holder swivels is carried by a member 6 mounted on a pin 5 and having depending limbs 29, 28 alternatively contacting a surface 32 so as to give one or other of two predetermined inclinations of the pin 7 to the face of the grinding wheel 3, e.g. 13 degrees (giving a drill point angle of 116 degrees) and 20 degrees (giving a drill point angle of 130 degrees). In the first position, i.e. with .limb 29 operative, the front carrier 14 is adjustable on a plane parallel to the face of the grinding wheel 3; adjustment of the front and rear carriers 14, 19 is effected as in the prior Specification. The adjusting screws 14a, 19a may be replaced by quick adjustment devices comprising discs 53, 59, Fig. 6, supported by the carriers and having notches 54, 54 co-operating with pins 50, 57 on the member 11 and on block 56; the carriers are locked in adjusted position by wing nuts 55, 60; the discs are held in any desired position by frictional engagement but may easily be adjusted to different positions. The pin 5 projects for both sides of an extension 10 of a slide 4<SP>1</SP> mounted on bars 9, 9 carried by a slide 4 adjustable in a plane parallel to the face of the grinding wheel; the member 6 is placed on the projecting pin 5 on one side or the other of the extension 10 according to whether the drill is right-handed or lefthanded and is clamped thereon by a nut 34 or 35. For the second position the slide 4<SP>1</SP> is moved away from the grinding wheel against an adjusting device 33 and the member 6 tilted forwardly until the limb 28 is operative. The slide 4<SP>1</SP> is moved on the bars by a screw spindle 38 having a handwheel 39. A cross member 40. Fig. 5, slidable on the bars 9 and clamped in adjusted position thereon by screws 41 comprises a bar 42 freely movable in a bore 36 in the slide 4<SP>1</SP>; the bar carries three graduations 43. The cross member 40 also comprises a diagonal guide having a scale 45; a slider 46 is adjustably mounted on the cross member, and is secured in adjusted position by screw 48 engaging a slot 47. In use, the member 40 is adjusted until a desired mark 43 (corresponding to one of three ranges of drill sizes) on the bar 42 registers with the rear edge of the slide 4<SP>1</SP>; the slider 46 is then adjusted so that a mark 49 thereon registers with a graduation on the scale 45 corresponding to the drill diameter, and the slide 4<SP>1</SP> is retracted by operation of the handwheel 39 until its rear edge abuts the slider 46.