Quote Originally Posted by Ole
A thread gauge can be a useful thing to own...

Back in the Rapid Rectilinear days there were no standards. Shutters were made in a bewildering number of sizes and threads - they were made to fit the lenses rather than opposite. Don't expect a lens from one maker to fit into a shutter for a lens from another maker!

If you have a couple of other lenses, you can estimate the focal length of the unknow one by using the technique described in this article: http://www.apug.org/forums/article.php?a=146 .

BTW, a Rapid Rectilinear almost certainly has "imperial" threads. If it were metric it would be an Anastigmat (same lens, different nationality).
Um, Ole, if I have it right threading for UK-made lenses was standardized -- RPS standard, described somewhere in the Vade Mecum -- by the time RR lenses came in. But Wayne's is US-made, by Ilex in Rochester, NY so if its threading conforms to a standard the standard probably isn't the RPS one.

Also, are you sure that RRs are anastigmatic? I ask because if I understand things correctly they were displaced by a variety of anastigmats. And in Lenses in Photography, Kingslake is explicit that the first anastigmats were invented long after the RR.

Wayne, from your many posts I've formed the impression that you're one of the cheapest people in existence -- I'm cheaper than you, so don't feel too proud -- but I think you've just outdone yourself. You have a suspect lens that you can't make right and you want to replace the elements from something else, required spacing unknown, and go forwards. This seems pretty, um, optimistic. You've just earned the Murray Leshner Extracting Expensive Lemons From Free Lemonade Award.

But if you're looking for lenses that will work on 6x9 and that don't cost much, anything from an old Kodak folder that uses film no smaller than 120 will do. These lenses' drawback is that the ones for films larger than 120 are longer than normal for 6x9. I have a couple of B&L Tessars, both longer than 4", that don't shoot badly on 6x9. Or look for a cheap 101/4.5 Ektar or Raptar.

Good luck, go on having fun,