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Fitting a new thumb safety for a 1911

Discussion in 'Gunsmithing and Repairs' started by IrvJr, Dec 18, 2007.

  1. IrvJr

    IrvJr Well-Known Member

    Hi All,

    I have a Kimber 1911 that I bought used. The previous owner installed an ambi safety. I would like to switch out the existing ambi safety for an Ed Brown non-ambi safety.

    I've looked at some online resources (M1911.org / brownells, a gunsmithing book by Patrick Sweeney, and Kunhausen's book 1) and have read about the thumb safety and how to fit a new safety to a gun.

    I've also removed the grip safety and spring plunger from the frame of my 1911 and I've been looking at how the thumb safety installs and interacts with the sear. I have some questions regarding the existing safety and installing a new one:

    1. I've done a safety check, and if I use the existing ambi safety, the hammer will NOT fall if the slide is installed, the hammer is fully cocked, and the thumb safety is up. However, if the slide is removed, and I push the safety a little higher than its normal "SAFE" position, the safety does not fully block the sear and if I press the trigger, the hammer will fall to half-cock position.

    Is this condition with the existing thumb safety OK or was it improperly fitted by the previous owner?

    2. I've replaced the original safety with the new safety and have tried to see where on the new safety I need to file down in order to have the safety properly fit within the frame. However, it's kind of difficult to see exactly where the new safety is interfering with the sear.

    What is a good way to determine what areas of the new safety need to be filed/dressed in order to make clearance for the sear?

    I've tried scoring the new safety with a pin or a carbide scribe, but I really can't get the tip of the scribe into the channel to accurately trace the edge of the sear against the safety. I've also tried using smoke from a candle (recommended by Pat Sweeney) to cover the new piece and then pressed the piece against the sear to see where they contact, but this didn't work well either.

    3. I've looked at some reference documents/sites (including the very nice Adobe animation on the M1911.org site) to try and see how the safety interacts with the sear. However, I haven't found one that clearly shows how the safety interacts in its on and off positions with the sear.

    Can someone explain/point me to a diagram/or show me how the safety interacts with the sear?

    I understand that the safety blocks rearward motion of the sear when the hammer is cocked, but I am having a hard time seeing how the geometry of the thumb safety's lug interacts with the sear in on and off positions. Ideally, if I could cutout or make translucent the right side of my gun's frame, I could see more clearly how this works.

    4. The safety that came with my gun has the safety lugs filed on both sides of the "L" shaped notch on the lug.

    Am I supposed to file both sides of the notch on the lug or only one side (the rearmost side when the safety is installed in the gun)?

    5. Can someone post some pictures of what their safety's fitted lug looks like? I realize mine will need to be different, but I'd like to see where other people's safeties have been relieved and compare it with my existing and my new safeties.
    Thanks for your help. I can always take the gun to a local smith to have the safety installed, but I would like to try and fit one myself to learn more about my gun. I've installed other things (like a match trigger and an extractor) and can do basic maintenance (tune extractor, fully disassemble the gun, etc.). If possible, I'd love to be able to fit my own safety. I don't mind wrecking a couple of safeties to learn how to do this - and of course, I will always do a thorough safety inspection before firing the gun and only load one or two factory rounds when I do test fire it at the range.

    Thanks in advance.
  2. 1911Tuner

    1911Tuner Moderator Emeritus

    Normal. When the slide is off, the safety lug moves up far enough to fail to completely block the sear.

    Copying the cut onto your new safety is not a guarantee that it'll work like the old one.

    Assemble the gun without the grip safety to better see how the parts interact...and to better see exactly where and how much of the point on the new safety needs to be cut.

    Don't be surprised if you kill the new safety on the first try. It's part of the learning curve.

    Luck to ya!
  3. HomerSimpson

    HomerSimpson Active Member

    Chuck Rogers has a sticky on another forum discussing safety fitting and includes some good photos.

    I hope posting a LINK is OK here.
  4. IrvJr

    IrvJr Well-Known Member

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