Well, to add to the fun, the range of screws in the model shop that looked
like they might be the right size were called "0-80 x 1/4" and "0-72 x 1/4".
The ones for the Rolleiflex were a tiny bit smaller than the 0-72, but a lot
bigger than the 0-80.
The metric 2x... ones were sensibly named, but the screws in question were
about 1.5mm or so across, so I don't think that 0-72 = 1/72nd of an inch,
either
There are literally dozens of screw thread standards and designations,
though only a few relevant to photographic equipment. An ANSI list can be
found at:
http://www.simpsonenterprises.biz/tech_specs_ansi_thread.html
The examples you give are "Unified Inch Screw Threads" in ANSI terminology.
Some history at:
http://users.pipeline.com.au/aandb/expert/vee.html
The "0" is a code for the screw diameter (approximately 0.06"), with codes
beginning at 0 [there are also 00 and 000 sizes, as the scale was extended
in the other direction]. The "80" is threads per inch.
In household use, you're probably familiar with 6-32, 8-32, 10-24 and
similar sizes; same terminology.
There's another standard, from ASME, for even smaller screws (Unified
Miniature Screw Threads). Story at:
http://www.normas.com/ASME/pages/B1.10M.html
Michael
P.S. Mostly distilled from Google searches, I don't really know all of this
:-) .
< This message was delivered via the Olympus Mailing List >
< For questions, mailto:owner-olympus@xxxxxxxxxxxxxxx >
< Web Page: http://Zuiko.sls.bc.ca/swright/olympuslist.html >
|