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  1. #11

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    Isn't the 39mm thread a standard metric one ? Any metal shop can put a hole is some steel and thread it for you, though it would be more convenient (and probably cheaper) to find one ready made. The idea of packing epoxy round a greased thread can work too - I have tried that succesfully for ventilation system parts with good results.

  2. #12
    ic-racer's Avatar
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    Quote Originally Posted by MartinP View Post
    I Any metal shop can put a hole is some steel and thread it for you, though it would be more convenient (and probably cheaper) to find one ready made. The idea of packing epoxy round a greased thread can work too - I have tried that succesfully for ventilation system parts with good results.
    Yes, any shop that is making 39mm Whitworth threads So, on this continent that would probably be SK Grimes....

  3. #13
    Jim Jones's Avatar
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    Quote Originally Posted by MartinP View Post
    Isn't the 39mm thread a standard metric one ? . . .
    The LTM is 39mm in diameter, but a 26TPI Whitworth thread See http://en.wikipedia.org/wiki/M39_lens_mount for one explanation.

  4. #14

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    A 39x1 mm ring will jam.

  5. #15

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    Quote Originally Posted by Jim Jones View Post
    The LTM is 39mm in diameter, but a 26TPI Whitworth thread See http://en.wikipedia.org/wiki/M39_lens_mount for one explanation.
    Ooooo, it seems that the Leica thread is indeed not a Metric one. I vaguely recall reading about the FSU pre-war thread vs. Leica difference, but didn't appreciate the reason.

    Strangely the Wiki article is a bit wrong too, or at least misleading. The Leica thread seems to be British Standard Fine (BSF), which is one of the Whitworth family but not the 'standard' thread pattern. The normal Whitworth thread is very robust (a relatively heavy coarse pitch/profile) and can withstand a lot of corrosion before jamming unuseably.

    Quarter-inch Whitworth bolts used to be used for all sorts of garden and farm tasks in UK. I'm English (though I don't live there anymore) and recall when the vendors started selling 6mm Metric bolts to replace the 1/4" W it was quickly found that Metric Coarse was a better match for the functionality of the Whitworth design, though arguably not quite as robust.

    You could say that the standard Whitworth thread was more like Metric Coarse, while the standard Metric thread was somewhat similar in design to B.S.F. It stretches my memory a bit, but I think I recall that there was a very fine instrumentation-purposes thread as well. Luckily Leica didn't borrow that one, else we'd never get an over-tightened lens off - clearly they knew what they were doing!

  6. #16

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    nut(s)

    pm your address & I'll throw a Leica/Nikon/Minolta 39mm nut in the mail for you.
    Postage should run about a buck.
    Heavily sedated for your protection.

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