GB814599A - Automatic screw thread-cutting arrangement for a lathe - Google Patents

Abstract

814,599. Screw-cutting lathes. JEANNERET, J. L. Dec. 4, 1956 [March 21, 1956], No. 37091/56. Class 83 (3). A screw-thread cutting arrangement for a lathe comprises a support 5<SP>1</SP> clamped to the normal tool-rest, a tool-holding slide 1, Fig. 4, and an auxiliary slide 5, these slides being moved along the support perpendicular to the thread-cutting axis by a control handle 8 to space the slides apart by a toggle mechanism against the action of springs. The depth of cut of the tool 2 is determined by an abutment 17 on the slide 5 engaging an automatically indexible member 6 having a number of stop faces at varying distances from its axis. Threadcutting is performed with the parts in the position shown in Fig. 7. At the end of the cutting stroke a fixed stop 10, Fig. 4, strikes the end 37 of a bell crank 9 pivoted on the slide 5. The opposite end of this lever has a latch 30, Fig. 7, which releases another lever 26 connected to the spindle carrying the handle 9. The latter is rotated anticlockwise by a spring plunger 33, and a roller 25 on lever 26 is thus brought out of engagement with a ledge 27 on the slide 1. This slide is then free to be retracted by a spring 13 to relieve the tool from the work and bring the slide against an abutment 12 on the support. The slide 5 is also now free to move forwardly to the same abutment 12, impelled by a spring 15 which is weaker than the spring 13. To re-set the tool with an increased cut ready for a fresh cutting action, the handle 8 is first pulled back in an anticlockwise direction to index the stop 6 (see below) and then rotated to the full extent in a clockwise direction. The latter movement forces the slide 5 back against the stop 6 and then, with the roller 25 engaging the ledge 27 on the tool slide 1, this is forced forward to a new depth-of-cut position. The latch 30 finally engages the end of lever 26 to hold the parts in their set position. A lever 43, Fig. 10, on the lower end of the spindle 40 of lever 8, when the latter is moved anticlockwise, moves a ratchet mechanism 45, 46, 57 to index the stop 6. The ratchet may be released to return the stop to the " start by a push-button 54.