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Thread: 61 Springfield lock plate threads

  1. 61 Springfield lock plate threads

    The item at issue is an original 1861 Springfield ( Springfield Armory) lockplate that needs the bridle screw hole rethreaded( I bored out the the original broken off screw on a milling machine( no PB blaster/ gentle heat/screw extractor was moving that thing) so the threads are still in there and the dia of the hole is OK to rethread for an original screw).

    The original screws are .182" major diameter and 26 tpi thread pitch; it's not really a true v form thread, more rounded, at least on the screws.

    If I was a clod, I suppose one could do it with a 10-24 tap and force the screw in but that's not going to happen. Before I make a custon tap, I was wondering if anyone knows of a source of such a tap or has other ideas.

    Note that it's a "fine" lockplate, not to be boogered

    Thanks

    AB

  2. #2
    rachbobo is offline Banned
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    Re: 61 Springfield lock plate threads

    If the original threads are fine but slightly rounded I'd leave the lock plate as it is to keep the lock original.
    I have rethreaded many a european metric lock to american threads but they were run of the mill hunting rifles so it was no loss.
    I searched for non standard taps and dies but found them very pricy for a one time job.
    I'd suggest finding a machinist to custom make new screws with the original thread.
    Another option is to take a screw blank and get it red hot to soften it.
    Then slowly carefully work it into the original hole letting the lock plate act as a die. I have found that many lockplates are tempered or hardened like the metric ones I worked on before.
    I have used a Vee diamond " Swiss File" to cut a shallow Vee into the hardened lockplate threads. That turned the lockplate into a threading die for me.
    Be careful and work slowly with plenty of oil.
    Once done you can harden the screw if needed.

    Bill Cheek

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    Southron Sr. is offline
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    Re: 61 Springfield lock plate threads

    According to my 2005 Dixie Gun Works catalog,(page 661) the thread on the M1855 sear screw is very close to the 5mm x 1.0 pitch.

    As the sear screw and bridle screws have the same thread and of course, the M1861 and M1855 have many parts that are interchangeable (like the sear screws)I would suggest that you check out the 5mm x 1.0 tap and see IF it will fill your needs.

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    GPM is offline
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    Re: 61 Springfield lock plate threads

    S&S firearms list in their catalog the tap you need, for the 61 springfield internal screws. If you don't have a catalog let me know and I'll look up the item #.

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    GPM is offline
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    Re: 61 Springfield lock plate threads

    I may have spoke to soon. The item # is SA183, but I think it's for the sidelock screws.

  6. #6
    Blair is offline
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    Re: 61 Springfield lock plate threads

    The original screws in the lock plate are 10- 26, M-1855 through M-1864.
    S&S Firearms does offer taps for this thread dia. and pitch.
    Internal and side lock screws are the same on Springfield made guns of this period.
    Hope this helps,

  7. #7
    Jack C., 69th NY is offline
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    Re: 61 Springfield lock plate threads

    S&S Firearms can be reached at 718-497-1100 or through their web site at http://www.ssfirearms.com/ They have what you are looking for.
    Jack Conway
    69th NY

  8. Re: 61 Springfield lock plate threads

    Thanks to all for the info etc. Just FYI here's what I found/did:

    The tap mentioned by some is not on the current online S&S catalog (although I did not call them), but more to the point as discussed in a post on the BB about 5 yrs ago the major thread dia of the lock retaining bolts are very slightly larger than the bridle/sear screws (.192" vs .182") The bridle screws will go into the lock retaining bolt holes but the retaining bolts will not go into the bridle holes. TheS&S tap was/is evidently ( based on the old post)sized for the retaining bolt holes. Holes threaded with it wouldprobably still work OK for the bridle screws, but assuming the plate is as hard as most of them are you would very likely bust the tap.

    In any case, wanting to avoid all that, I made a proper sized tap from O-1 tool steel and...carefully...ran it into the hole I had drilled thru the center of the busted screw. As I hoped it picked up the threads in the plate and took out the "sleeve" that was what was left of the old screw. Problem solved and now have a perfect original GI screw hole.

    Thanks

    AB

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    GPM is offline
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    Re: 61 Springfield lock plate threads

    Doesn't matter now that your problem is fixed, but the part # for the above tap was from their on-line catalog. pg 66 under shooting acessories.

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