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
