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Thread: Rethreading screws (the search for replacement screws)

  1. #11

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    Re: Rethreading screws (the search for replacement screws)

    Quote Originally Posted by Drew Wiley View Post
    oddballs like Whitworth, "British metric", or custom wholly nonstandard., willy-nilly wholly nonstandard screws are more apt to be current Chinese or Indian junk screws,.
    Drew,
    I think you are showing an unfortunate bias.
    The ‘oldballs’ are in fact standardized thread forms that have or had a specific purpose. For instance, pipe, gas, cycle, microscope and instrument threads. Also there are left hand threads, multi-start threads, tapered threads, as well as industry- specific threads.
    There are also differences in thread forms - for instance acme – and similar threads but with various pitch angles.
    Your ‘ willy-nilly wholly nonstandard screws are more apt to be current Chinese or Indian junk screws’ tend to be cast– hence they do not [cannot] have the precision of machined screws.

    Regards
    Tony

  2. #12

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    Re: Rethreading screws (the search for replacement screws)

    Quote Originally Posted by Jimi View Post
    I bought some tools to get a more exact measure, since a loupe and a ruler is too rudimentary in this case. I am going to see if I can make a photo of the screw too, just to show the damage.
    For pitch measurement a ruler can be sufficient if you measure over 'N' pitches the more the better, then divide that measurement by [N-1]. For diameter use a micrometer [without inferring anything 25.4mm = 1 inch so multiply or divide as appropriate].

    Alternatively, if there is a second identical but undamaged screw take that to a hardware store and see if you can find a nut that fits.

    regards

    Tony

  3. #13
    Between here and there
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    Re: Rethreading screws (the search for replacement screws)

    Thanks Tony,

    I took one of the undamaged ones to the local store but no luck there, since they only have standard m5 nuts, which jams almost immediately - "sir, the threads on this screw must be damaged, I think". I'll go downstairs and see if I can measure it a bit better with the ruler again, otherwise the thread gauge will arrive tomorrow.

    Somewhat unrelated, I happened upon a treatise about the finer details of JIS threads, and it amazes me how much there is to see and know.
    "Be still and allow the mud to settle."

  4. #14

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    Re: Rethreading screws (the search for replacement screws)

    Quote Originally Posted by Jimi View Post
    otherwise the thread gauge will arrive tomorrow. .
    if I remember right, thread gauges are specific to thread forms - so a metric thread gauge will do metric threads, but will not fully identify the pitch of other thread forms.

    Anyway have fun

    regards
    Tony

  5. #15
    Tracy Storer's Avatar
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    Re: Rethreading screws (the search for replacement screws)

    I still don't see anywhere where you tell us what the screw goes to (ie: what camera?)
    Tracy Storer
    Mammoth Camera Company tm
    www.mammothcamera.com

  6. #16
    Drew Wiley
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    Re: Rethreading screws (the search for replacement screws)

    Hi Tony. I once worked at a specialty supplier to machinists and mechanics that had an amazing selection of bolts, screws, taps and dies, etc. - all kinds of special applications almost impossible to find anywhere today - special antique lock threads, gunsmithing taps different from anything else, and yes, totally unique threads deliberately designed to prevent people from repairing their own import cars - even corkscrew left-hand pitches that no thread gauge will read. We did business with over fifty different car importers, and all but one had crooked repair departments; and many of the auto models themselves had all kinds of deliberately engineered flaws to keep dealers successful - repairs have always been more profitable than actual auto sales. That's still the case today. But the fellow in charge of that particular department back then was an ex-NASA optical machinist, so really knew his stuff. I guess you could say all of those things were somehow "standardized"; but my "standard" response to Brit machinists is that if Napoleon had won at Waterloo, everything would be a lot simpler today.

  7. #17

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    Re: Rethreading screws (the search for replacement screws)

    Quote Originally Posted by Drew Wiley View Post
    but my "standard" response to Brit machinists is that if Napoleon had won at Waterloo, everything would be a lot simpler today.
    Hi Drew, in terms of what if
    How about if the lower 48 and Hawaii were still part of the British Empire and Alaska still belonged to Russia

    regards
    Tony

  8. #18
    Between here and there
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    Re: Rethreading screws (the search for replacement screws)

    I updated the first post to be a bit clearer - with a photo of the screw and where it is going (swing mechanism of a Sinar Norma). I am putting it here too, in case someone can't be bothered to read again.

    As for the thread size, I have now tested it against my thread gauge, and it does not seem to be metric. The closest I get is Whitworth (24 G it says) but it still not correct, since there is space between the threads and the gauge. It is unlikely that I get any sort of answer from Sinar, so I may be stuck, unless someone else actually knows.

    I once had a similar problem with missing screws on an Oschwald era Arca Swiss. It turned out that it was a JIS thread on that screw, even though the first assumption would be a DIN metric thread.

    This is just leftover parts, so I can leave as it is, but it would still be nice to be able to return the standard to a functioning state. I could wrangle past this issue, by putting the screw on the swing lever side and get some thicker flanges to cover the bad part of the thread.
    Attached Thumbnails Attached Thumbnails Screw Sinar.jpg  
    "Be still and allow the mud to settle."

  9. #19
    Tin Can's Avatar
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    Re: Replacement screw for Sinar Norma

    Now we know

    Many here including me have Sinar Norma

    That kind of damage may be 'fixable' to 'good enough' with a thread file, or even just a tiny triangular file

    Thank you for a picture and description
    sin eater

  10. #20
    Drew Wiley
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    Re: Rethreading screws (the search for replacement screws)

    It will be metric of some sort. Everything on my Norma is. A bit of slop can be taken up by Teflon tape if necessary. The Swiss hypothetically ever adopting Whitworth would be equivalent to them giving up chocolate and drinking tea with milk in it instead. The whole Brit system of 1/12 of a cubit-furlong-squiggle was originally based on how far a Druid priest drunken on mead could throw the head of an ox.

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