Thanks, Jon, this was very illuminating after many decades of lathe turning practice! Peter
Am 02.04.2014 19:22, schrieb Jon Elson: > On 04/02/2014 08:39 AM, Peter Blodow wrote: >> I don't even know what threading dials are and where they are installed, >> sorry. I usually cut a thread up to a given length, then stop and >> retract the tool in one instance. It's a two hand job. I can put the >> drive directly in reverse for a fraction of a second instead of a brake. >> > OK, this apparently is big difference between US and metric > practice. US (and old British) lathes in the unified Imperial > system had standard threads that were all multiples of 8. > So, we had 20, 24, 32, 40 TPI. You could disengage the > half nuts and re-engage on any thread for most of the > standard thread pitches. For some odd pitches such as > pipe threads, you could only engage at one inch intervals. > The thread dial had various marks so you could be sure > to engage at the right multiple for the thread you are > cutting. It is much faster to open the half nuts, back > up the carriage with the handwheel and re-engage > at the right mark on the dial. I could usually do this > in about 2 seconds, including backing up the X and > feeding back in. I'm sure reversing the spindle and > then going back to forwards would have to take longer. > > But, with the various metric standard pitches, this > nice multiple relationship probably doesn't hold > for practical leadscrew pitches. > > Jon > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > Emc-users@lists.sourceforge.net > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list Emc-users@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/emc-users
