Not really, Jon, all the metric/Whitworth-conversion is done within the feed gear box. I can select between 60 metric and imperial feed rates each. I switch metric to imperial with the flic of one lever. This is done, however, by a combination of gear wheels (34/26*79/41) to avoid the use of a giant 127 teeth wheel. This gives a slight error of 0.8% in case of metric screw cutting which, however, has never led to difficulties. This means, the machine has been actually designed for Whitworth threads. There is no problem in disengaging the half nuts, re-arranging things and closing again. Multiple pass cuts are, of course, always done by retracting the tool und reversing the drive. For each pass, I give the tip a tenth mm additional feed with the top slide screw to make sure it will cut mainly in forward direction.
The screw itself is, as I said before, 4 threads to the inch (6.35 mm pitch) although inches were never used in Italy. My machine is a Graziano SAG 12 (italian brand), very convenient for automation because of the magnetic clutch speed selection. Best regards Peter Am 01.04.2014 18:43, schrieb Jon Elson: > On 04/01/2014 10:32 AM, Peter Blodow wrote: >> Until the early 1990ies, many lathes were produced in Germany with inch >> screws and a 127 teeth gear wheel to drive them in order to end up with >> metric threads. >> > But that means you can't disengage the half nuts and > re-engage them > for the next threading pass. Seems like a very hard way to go > for production, although perfectly acceptable for rare cases > where > you need a thread the lathe can't provide. > > Jon > > ------------------------------------------------------------------------------ > _______________________________________________ > Emc-users mailing list > [email protected] > https://lists.sourceforge.net/lists/listinfo/emc-users > ------------------------------------------------------------------------------ _______________________________________________ Emc-users mailing list [email protected] https://lists.sourceforge.net/lists/listinfo/emc-users
