The tool page he reference was M42-5 not M42-1 JC O'Connell hifis...@gate.net
-----Original Message----- From: pdml-boun...@pdml.net [mailto:pdml-boun...@pdml.net] On Behalf Of Paul Ewins Sent: Wednesday, April 01, 2009 9:23 PM To: Pentax-Discuss Mail List Subject: Re: do any m42 adapters do auto stopdown? >> M42x1 would be the same regardless of whether it is photographic equipment or heavy machinery since it describes a thread with a 42mm diameter and a 1mm pitch. There is no guarantee that something (other than camera equipment) described just as M42 wouldn't be M42 x 0.75 or M42 x 1.25, but I would bet that any M42 lens would be M42x1. Accrording to wikipedia Leica thread mount is M39 x 26tpi (whitworth) which works out at M39x.977. Apparently early Zorki and early Canon RF cameras used M39x1. It gets really murky in the world of large format lenses and shutters where some of the metric sizes are very close to imperial sizes and you need to measure very carefully to work out exactly what you have. Prior to WWII there weren't any real standards and lots of oddball sizes exist. Paul >> On a related note, is what we call m42 the same as what machinists >> call M42? >> >> http://www.besly.com/catl/catl4124ps.htm#M42 > > Yes, I think so. Leica screw mount is M39. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions. -- PDML Pentax-Discuss Mail List PDML@pdml.net http://pdml.net/mailman/listinfo/pdml_pdml.net to UNSUBSCRIBE from the PDML, please visit the link directly above and follow the directions.
