Unusual problem with stuck rear lens cap

Discussion in 'Nikon' started by sjmurray, May 29, 2020.

  1. Untitled-1.jpg I had an unusual problem I’ve never experienced using Nikon cameras and lenses since the late 1960’s. I recently literally could not unscrew the Nikon rear lens cap from my Nikkor 28mm Ais f 2.8 lens! I even tried a large pliers. I finally removed it by carefully sawing it nearly in half with a hacksaw (fine tooth metal saw). See photos. It appears the lens cap I had used was a newer one which has a much wider outer rim than older lens caps. The width of the rim of the cap became jammed into the indented outer rim of the lens. See the photo of the two types of Nikon rear lens caps. I was able to do this without damaging the lens, thank goodness.
    steve_g|2 and mag_miksch like this.
  2. I'll remember this- and will also compare the LF-4 against my LF-1 caps using some calipers.
  3. ShunCheung

    ShunCheung Administrator

    I started using Nikon a few years after SJMurray but have never had this problem. I still have a couple of AI/AI-S lenses, and I just put a latest rear lens cap on my 43-86mm/f3.5 AI that I bought in 1977 and tightened it. I don't really see how it can get so stuck.

    It is over now, anyway, but I wonder whether one of those jar openers could have helped.

    _DSC1897.jpg _DSC1898.jpg
    mag_miksch likes this.
  4. I have a couple of LF-4 caps, and tried them on a bunch of lenses. They easily clear the skirts of pre-AI, AI, and AIS lenses from 1961 to current in my collection, but one I don't have is that particular 28 (mine is the oldest version of the oldest 28/3.5). I thought for a moment that perhaps this cap was shallower and bumped into the protrusions on the lens, but it doesn't seem to

    ABout the only thing I can think of is that the cap was over-rotated and caught. It occurs to me that you should check that the tiny screw in the mount (underneath the flange, about 90 degrees clockwise of the aperture stop-down lever as you face the rear of the lens) has not fallen out. That is the only thing preventing the lens from over-rotating or being removed backwards in the camera, and if it's gone it will hang up on the aperture lever and bend things badly. It's happened twice to me over the years, fortunately both times on a Nikon F whose back could be opened up, and whose brass lever could be re-bent.
  5. Sandy Vongries

    Sandy Vongries Administrator Staff Member

    There is a significant variation in sizes from pre AI to current lenses. I have yet to find one too tight, but quite a few lens changes where the cap was less secure than I would like. I suspect that two elements with enough mismatch came together. Nothing in my old Nikon references address the issue. Good and thoughtful approach and skill got the OP out a winner.
  6. Well, I went back and re-attached another LF 4 lens cap to the same lens, cautiously, and tightened pretty fimly. No problem this time. The fit was OK. I really don't know what caused it to be so impossibly tight that one time. I generally don't really "crank" the lens caps on anyway. Shun, I actually tried a large Channelock pliers designed for plumbing fixtures and that didn't loosen it!
  7. Matthew, I located the little screw you were referring to and it is there.
  8. V. strange. The wider rim should actually present less pressure against the lens-mount and not stick so easily.

    BTW, the cap on the left of the above picture isn't the genuine Nikon article. No Nikon-made cap has a letter N stamped inside it, and Nikon's outer serrations aren't that style. Having said that, I would rather use Tamron caps on the rear of all my lenses; they tend to lock and seal better than Nikon's own, and the larger diameter gives you a better grip on the cap.

    I've never had a jammed rear cap. It's usually the opposite problem - getting a cap to stay put after a bit of wear has taken its toll. Tamron's caps seem to hold up better over time as well. I always look in 'rummage bins' for Tamron caps, but they only rarely get left to scavenge.

    P.S. You were turning the cap the right way I presume? It's effectively a left-hand 'thread', and the righty-tighty, lefty-loosey rule doesn't apply.
    Last edited: May 31, 2020
  9. A few years ago i had the same problem with the same lens, i could happely solve it by cooling it by usiage of "Cold spray" wich i also use for finding defects in electronic devices.

    On inspection the cap showed to have an imperfection at the edge, since then i check every new lens and bodycap, and treat it with a fine a key maker file to ensure it is smooth ..
    sjmurray likes this.
  10. FWIW, here's a quick snap of an Ai-S era genuine Nikon LF-1.
    It doesn't look that much different from an LF-4 to me.
  11. ShunCheung

    ShunCheung Administrator

    I wonder why an BF-1 wouldn't fit AF bodies, which may have an additional "screwdriver" AF mechanism, but that should not affect the mount. Clearly AF/MF lenses can fit both types of bodies.

    I bought an FT3 in 1977 at the very beginning of the AF era and then an FE the following year (1978). But I recall those bodies didn't come with BF-1 type black plastic body caps. All I got was a white, translucent body cap that fits over the mount like a plastic cap for a can, without any prongs that locks itself onto the body.
  12. ShunCheung

    ShunCheung Administrator

    Strange. There is no moving part on the rear lens cap. I wonder why that particular cap got so stuck on your lens.
  13. I have had rear Nikon caps that wouldn't tighten at all on some lenses, practically fell off.
  14. Yup, me too.

    Genuine cap on genuine lens...no friction grip at all.
    Sanford likes this.
  15. c.p.m. probably hit it: a lens cap with an imperfection on the edge. By the time I got it off it was pretty destroyed to analyze. I have a LF 1 which is slightly thinner on the edge compared to the LF 4 20200531_5886.jpg See image.
  16. And likewise - hence my acquisition of a solution which clips on. I've not taped the cap up and filled the hole yet, though. I don't really know why Nikon never made a lens cap with at least a bendy plastic anti-rotation clip - it can't have been hard to do. (I also don't know why the body caps don't clamp in, although to be fair it's only my F5's push-on one that ever comes off.)

    If a manufacturing defect can cause it to wedge, that's still a design flaw...
  17. sjmurray,
    Sorry for your troubles. Have never had a rear cap stuck but have had problems with front caps to teleconverters sticking.
    You have to visually confirm that the dot on the cap matches with the telconverter. It’s can’t be done by feel.
    Just was checking a lens yesterday and discovered a Zeiss cap for my 15mm on a Tokina 10-17 zoom fish eye.
    I just could not let that set, elsewise the magnet poles of the earth would reverse, so I quickly changed them.
    Good Hunting
  18. Body caps are easily modified to lock into place. They just need a 2.5 ~ 3mm hole drilling in the inner rim to coincide with the locking pin on the camera mount. All you have to do then is remember to push the lens release before twisting the cap off.... and, OK, I've forgotten the mod on a few occasions, and then wondered why I couldn't get the body cap off. That's until my memory came back to me.
    Andrew Garrard likes this.

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