GB633060A - Method and apparatus for manufacturing twist drills - Google Patents

Abstract

633,060. Making twist drills. DELANEY, H. W. Oct. 26, 1945, No. 28268. [Classes 83 (ii), 83 (iii) and 83 (iv)] Rolling helical grooves; twisting; working at specified temperatures.-In a method of manufacturing twist drills, stock of multiple drill length is heated and fluted with beads formed along alternate edges of said flutes, thereafter the fluted stock is twisted into drill form. Drills are then finished by cutting to length, grinding and pointing. The stock smaller in cross-section than the finished drill is raised to a temperature between 1800‹ and 2100‹ F. and flattened between a pair of rolls 9, 11, Fig. 2, one, 9, of which has flanges 10 in which the rim of the coacting roll locates. The flattened stock emerges at the correct angle for entry to a pair of rough fluting rollers 12, 13, Fig. 3, relatively adjustable in a horizontal or vertical plane, and is then finished by a further pair of rolls, identical in form, but arranged in closer relation to one another in order further to impress the flutes and the beads. The various roll pairs are mounted in separate housings slidably mounted on ways on a base so that varying lengths of stock can be rolled by altering the relative positions of the housings. The work is then subjected to an air stream to equalize the temperature throughout its length and is twisted in a machine having a pair of relatively adjustable twisting heads 22, Fig. 10, slidable on a base 23. The heads comprise a housing 34, Fig. 14, with a member 43, slidably mounted on two bars 44 extending from the housing. Springs 48 are interposed between the housing and member 43. Secured to member 43 is a self-locking and unlocking driver having an inner member 39 secured to the member 43 by a split ring 40 and a brake lining 41. The outer body 38 has a hollow shaft 37 integral therewith which is splined on its outer surface and enters above in housing 34 where the splines engage in a gear 35. The work is received in the hollow shaft 37 and is driven by pins 47 pivoted on fingers 45, Fig. 16, whose ends engage recesses 46 in the body 38, when the latter is rotated in the direction of the arrow, and move the pins apart to free the work. Opposite rotation of the body causes the fingers to pivot inwardly and close the pins to grip the work. The direction of rotation of the outer chuck housing is transmitted through the gears 35 by splined shafts 26, 27, Fig. 10, which are oppositely rotated through further gears by racks 24, 25, carried by a cross-head 20, on the piston of a hydraulic cylinder 21. Limit switches 28a, 29a are provided to stop the movement of the head when engaged by the adjustable stops 30<SP>1</SP> or 31<SP>1</SP>, and a scale 32 and pointer 33 indicate the degree of twist imparted to the work 5, which shortens on twisting and automatically moves members 43 inwards against the action of springs 48. The rotation of the head is then reversed allowing springs 48 to return members 43 to their normal position and fingers 45 to free the work. In the next stage the outer diameter of the work is trued by rolling between platens 50, 51, Figs. 18 and 19, supported in a rectangular housing 52 and having bevelled edges 58 to ensure smooth engagement of the drill bit 5. The platen 50 is cut away at 57 to release the work which falls on to an indirect delivery track 55. The platen 50 is adjusted by means of screwoperated wedges 60 acting in conjunction with bolt 63 and spring 62. The rolling deforms the lands at 65, Fig. 22, so that when the metal indicated by the unhatched portion of the Figure is ground away after heat treatment, a hard and sharp edge 66 is produced.