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Thread: Restoration screw thread issue - Old unidentified pistol late 1700

  1. #1
    Associate Engineer
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    Jul 2018
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    Restoration screw thread issue - Old unidentified pistol late 1700

    Dear sirs,

    I recently came into possession of an old (end of 1700 circa), unidentified, cap lock handgun, 25cm long total, 12.7mm caliber (.50). It has an octagonal barrell, no decoration at all, the metal plate that fixes the mechanic is oval shaped, without any angles.
    The mechanic system is in perfect condition, the two main screws that fixes the metal plate supporting the mechanic and the barrel to the woods are...destroyed.

    The filetting of both the screws is elongated and twisted, like the entire screws, the screws are broken too, due to stress ( the wood gave away a bit and the screws alone had to support that kind of recoil). I wanted to brass wield the screws, with the oxy acetylenic flame, but i noticed so many creaks into the screws that it was impossible to fix them.

    And more is the issue about, what the hell was the right screw thread of both? I tried to measure it, and making them with lathe, then i had to cut the most deformed thread parts and retry again, it resulted as follow:

    Screw 1) 4.01mm diameter (precise), thread 1cm long of a W30 (closest to it)
    Screw 2) 3.36mm diameter (precise), thread 1cm long of a W32 or 0.75 metric (closest to it)

    Solution A)
    So, which one could be BSW or BSF type? There are the filetting files for these? Where can i found such stuff?
    The screws are 4cm long circa, the lathe would bend them, i need the filetting files.

    Obviously i dont want to remake the original plate's female threads, to adapt them, because these are perfectly fine and i want to keep the rest of the pieces as original as possible.

    Solution B)
    I live in EU, if somebody would have around some screws of that diameter (the length is not issue) and similar filettings (even more screws so to have a kinda of thread range maybe) i would gladly buy them and try them to identify the right ones.
    In central EU is impossible to get my hands on not metric thread screws.


    If somebody have any idea, my email is xxxxxxxxxxxxxxxxxxxx , contact me too if you wanna the pictures of the disassembled parts or more infos (measures and so on, maybe to identify that old gun)


    Thanks for the comprehension, best wishes.

  2. #2
    Principle Engineer Cragyon's Avatar
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    I doubt that the original screw thread was to any standard - just whatever the gunsmith preferred. I would just figure out what current industry minimum size you can open it up to using a tap/die or threaded insert.

  3. #3
    Associate Engineer
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    Jul 2018
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    That's what i feared, there isn't a way to get a "plaster" stamp out of the female threads and make both the screws thread with cnc or something?
    The things that is the best in a negative case, would be to fill the female thread with steel/iron and then make a new screw thread, just the issue is that filling it with wielding machine it would become too hard for the filettings files, mhhh.
    Last edited by zoichi_kanoe; 07-20-2018 at 02:36 AM. Reason: errors in typing

  4. #4
    Lead Engineer Cake of Doom's Avatar
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    Have you tried contacting any battle reenactment groups/forums? Going by the octagonal barrel, I'd suggest American groups. In time period you stated Europe was still using smooth bore flintlocks for mass use. My instincts are pointing towards a Naval officers pistol as it's too short for a duelling weapon. Can you post a picture?

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