Patent GB-353470-A (GB)
Title: Improvements in or relating to double thread screw cutting machines
IPC: B23G1/06
Filed: 1930-04-22
Abstract: 353,470. Cutting screw threads. ARENZ, J. A., 60, Broad Street, Mount Vernon, New York, U.S.A. April 22, 1930, No. 12476. [Class 83 (iii).] Lathes; tools.-In a machine for cutting doublethreaded screws, the tool is fed longitudinally of the work and is moved transverselv at the end d of the travel, to point the screw, the longitudinal feeding means being adjusted between successive traverses so that the tool follows the two threads alternately. The driving shaft 4 is driven from a pulley 6 through a clutch 5 and rotates a chuck 8 to which the blanks 9 may be fed automatically. The tool 11 is mounted on a holder 12 secured on a longitudinal shaft 13 which may be fed by means of a helical cam 15 and is also rocked to move the tools transversely of the blank by means of an arm 17 engaging a profile cam 18 carried by a saddle 20 pivoted coaxially with the shaft 13. The saddle carries an arm 22, Fig. 3, engaging projections on a depth cam 23 mounted on a cam shaft 25, the cam projections 24 being of progressively increasing height and being separated by spaces 26 so that the tool takes a slightly deeper cut at each successive working stroke and is withdrawn from the work during the return strokes. A collar 31 loose on the shaft 27 is provided with teeth 32 coacting with similar teeth on a fixed member 34. An arm 37 carried by the collar 31 is connected to an arm 38 mounted on an eccentric connected to a disc 41 having pins 42 coacting with a block 43 on the feed cam. During the revolution of the feed cam the block 43 engages one of the pins 42 and rotates the eccentric half a turn thus turning the loose collar 31 and causing its teeth to override the teeth of the fixed member 34. When the loose collar is moved back the teeth are restored to the meshing position. Thus the feed cam is moved alternately backward and forward for each cutting stroke of the tool the movement being such that the tool cuts on alternate strokes the two threads in the blank. In order to start the threads at diametrically opposite points on the blank the notches on the depth feed cam are arranged so that when the traverse feed cam is in its rearward position the tool is not moved into the work until the feed has commenced and the blank has made half a revolution. In a modification of the device for imparting axial movement to the traverse feed cam, the pins 42 may be carried on a pinion 44.engaging a gear 45 on a rotatable sleeve carrying a recessed collar 47 coacting with a fixed member 49. Thus when the pins are rotated by the cam projection 43 the gear 45 is rotated and the projections 50 are alternately engaged in the recesses 48 and on the surface of the collar 47. The shaft 4 carries a pinion 51 driving through gears 52, 53, 54 a gear 55 on the cam shaft 27 which is connected through further gearing, Fig. 2, with a cam shaft 58 and the depth feed cam shaft 25. The machine is provided with a sliding pointing-die 64 operated by a cam 68 on the cam shaft 58. A holder 70 carrying a single tool 72 may be clamped to the shaft 13 by a bolt 71, the tool being secured by a bolt 74 and being chamfered at 75 to form the cutting point. In some cases two tools 80 mounted on tool holders 84, 85, Fig. 11, may be employed.