How to assemble Canon FD 24mm 2.8 (breech-lock)?

Discussion in 'Canon FD' started by marklee, May 11, 2019.

  1. Hi guys,

    I had the rear cap stuck to the lens. Then, I removed two screws on the silver ring---biggest mistake.

    After the screw is removed, a metal stopper fall off. So I unscrewed three screws at the rear to take off the next layer to get the stopper out. Now I ended up with a lens that I can't put together.

    1) The location and the direction of the metal stopper is uncertain.
    2) The relative location of the aperture ring stopper is uncertain

    How should I put them back?

    Helps are really appreciated!
  2. cmuseum

    cmuseum cmuseum

    I don't have that exact type of lens at hand currently. But from my general experience with breech lock lenses my procedure would be like this:
    1. Remove the silver stopper and unscrew the breech lock ring from the mount assembly.
    2. Set aperture ring to "A" (or the green circle, resp).
    3. Lock the aperture control lever.
    4. Reinstall the mount assembly. Move the aperture signal lever while positioning it so that it matches the claw in the lens.
    5. Insert the three screws but don't fully tighten them yet.
    6. Unlock the aperture control lever and check proper function of the aperture levers and ring. If anything is wrong remove the mount assembly and try again.
    7. Insert the silver stopper in the slot at about the same position as the black stopper. You should be able to tell the correct orientation by matching the holes with the breech lock ring. (I think in your first picture it has the wrong orientation, but I am not entirely sure about this).
    8. Screw on the breech lock ring. Turn it all the way to the end of the thread, then turn it back until the holes match the holes of the silver stopper.
    9. Insert the stopper screws. This may be tricky. I always use a longer screw of the same size for "catching" and holding the stopper. If you don't have one a magnet may come in handy. If you cannot get the screws in remember the stopper position, disassemble again and start over with the stopper already installed.
    10. Tighten all screws.
    Don't loose the EE pin (3 o'clock position in second picture)!
    marklee likes this.
  3. Thank you very much for the detailed instruction, cmuseum.

    How about the focus during the whole operation? Should it be infinity or closest?
  4. cmuseum

    cmuseum cmuseum

    Focus position does not really matter. But setting it to infinity moves everything closer to the back and that may make installing the mount assembly a tad easier.
    marklee likes this.
  5. Thanks again, I will try on Monday!
  6. Picture1.jpg
    Thanks to the instruction, it was successfully installed. However, the metal pin (red arrow) is stopping me from installing an adapter.

    I wonder if I did any thing wrong during the assembly?
  7. cmuseum

    cmuseum cmuseum

    That's the positioning pin that ensures proper alignment of the lens with the mount. The mount has a slot matching this pin at the 12'o clock position.This pin has always been there since the early days of Canon R lenses and an adapter not having the slot is not a regular R/FLFD adapter.
  8. On You Tube mikeno62 takes an FD 24mm lens apart to service a stiff breech ring. I think if you can follow his procedure you might be able to fix your lens.

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