GB575529A - Novel or improved machine for use in forming a radius or radii on the outer end of a drill or like tool - Google Patents

Abstract

575,529. Sharpening drills. SEARCHLIGHT, Ltd., and DARBY, A. March 22, 1944, No. 5301. [Class 60] An appliance for use with a grinding machine for grinding radii on the cutting end of a drill comprises a cradle in which the drill is clamped, and which can be rocked about a horizontal axis, and is mounted in a carriage which can be swung about a vertical axis coincident with the centre of the desired radius. The appliance comprises a bed 10 which can be clamped to the cross slide of a grinding-machine and is furnished with a stud 11 engaging a bush 12 in the carriage 13. A pillar 14 extends from one side of the bed having an arm 15 in which is a sleeve 16 on which is a bush 19 on a pillar 17 on the carriage; by these means the carriage can be swung about the axis of the stud 11 and sleeve 16. The cradle 20, of half round section, is mounted on the carriage in bearings 19 and is formed with a recess to receive a bar 46 having a groove 21 in which the tool 22 is clamped by a pivoted screw-operated bearing piece 25, an arm 27 carrying the screw being provided with a lug 28 engaging a tooth 30 on an arm 31 pivoted to the cradle ; the arm 31 can be disengaged by means of a finger 31b. The drill is rocked about its axis as the radius is being formed to preserve the cutting angle at the tool edge, by means of a bar 34 bearing down on one side of the cradle against a spring 35 attached to a lever 37, the bar being pivoted to a lever 38 pivoted to a fixed pillar 39 and having a pin 40 engaging a fixed cam slot 41. The cradle is connected at its ends to links 43 pivoted to arms 44 on a rod 45 movable endwise through the bearings 19. The inner end of the lever 37 turns on the rod 45 and has an upward extension which engages in a slot 20a on the underside of the cradle and moves therewith. The lever engages a notch 47 in a plate 48 supported from the carriage at one end by a pin 49 engaging a slot 50, and at the other by an eccentric 51 by means of which the cradle can be adjusted endwise. The tool -is adjusted lengthwise by a poppet 54 operated by a screw 55 passing through a screwed sleeve 55a clamped by a screw 58. The swinging movement of the carriage is limited by a screwed rod 65, with an adjustable stop 67, pivoted to the pillar 14 and passing through a post 66 on the pillar 17. In order to form radial portions at the two sides of a flat portion, the front of the carriage is offset in relation to the pivot axis. For this purpose the carriage is divided and the upper part 13a has two screwed studs the rear stud 68a passing through a clearance hole in the lower part 13b while the forward stud 68 passes through a transverse slot whereby the parts may be swung relatively to one another about the stud 68a. The wheel is trued by a diamond 58 carried by a cranked member 60 mounted in the sleeve 16 and retained in an inoperative position by a handle 61 engaging a lateral projection 62.