STIFF BREECH LOCK RING

Discussion in 'Canon FD' started by NLsafari, Nov 26, 2020.

  1. I have a number of FD lenses and recently noticed that one of them has a stiff BREECH LOCK ring. With my other lenses when the red dots in the lens and camera are lined up and the lens engages the camera the BREECH LOCK ring moves automatically. This is important to me because I once was in a hurry and did not notice that the lens and camera were misaligned and I tightened the ring with normal pressure and I caused damage to both camera and lens mounts. So with the lens in question when the dots are lined up and it engages the camera there is ZERO movement of the ring. This is why I say the BREECH LOCK ring is stiff. However, the lens diaphragm works perfectly so I know the linkage is good. So is this a lubrication issue or is something mechanical in the lens mount misaligned or broken and how can I fix it?
     
  2. I've had a number of breech lock lenses on different bodies and to be honest, I've never relied on or even noticed the ring moving on its own. I've always assumed that you have to turn them manually to lock. Actually I wouldn't be happy with just relying on their own movement, I would always look to manually tighten them sufficiently to be confident they won't come loose.
     
  3. Yes of course you have to tighten the ring after it moves. I like the movement as an indicator that things are aligned properly before snugging things up.
     
  4. cmuseum

    cmuseum cmuseum

    Please note that the lower the aperture number is set the smaller is the movement of the ring. The movement is smallest at 1.2 or 1.4 and it is greatest at “A” (or green ring).

    The force that turns the breech-lock ring comes from a small spring inside the lens that also actuates the aperture signal lever. It's not a very strong spring as the camera has to overcome its force for transmitting the selected aperture number.

    The breech-lock rings are mildly lubricated and dirt can accumulate or the grease can get stiff. Cleaning and re-lubricating might help. Use very light grease.

    Theoretically, a mechnical issue with the aperture signal lever could also be the cause. But you already mentioned that the aperture is working well and hence this should be less likely.
     
    NLsafari likes this.
  5. Is the spring that activates the breech-lock ring lens specific or did Canon design a "FITS ALL" spring?
     
  6. Note that the earlier versions of the FD breech lock lenses do not have a spring inside the breech lock and must be closed by hand. Perhaps yours is an early version and is working as it should.
     
  7. I know that the breech ring use to move when the rear cap was put on the lens. So I think it is either the spring or the grease on the ring that is causing the problem.
     
  8. cmuseum

    cmuseum cmuseum

    According to part numbers, for the very early line-up of chrome nose lenses there have been at least 2 different springs. I don't know for later S.C. and S.S.C. lenses. If I had to make a guess I'd say that more variants of the spring were added with the broadening lens line-up.
     
  9. I saw a YOU TUBE video of a repair of a Canon FD 100/2.8 with a stiff breech collar and it looked easy. But the lens I am having a problem with is the FD 300mm F/2.8 SSC FLUORITE and I think I will pick up a cheap CANON FD lens on E-BAY and experiment on that first.
     
  10. Does anyone know if the Canon FD 2X-B extender have a spring in the breech lock mechanism?
     

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