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Lens help

Discussion in 'Adapted Lenses' started by jdcope, Jul 11, 2016.

  1. jdcope

    jdcope Mu-43 Regular

    92
    May 21, 2015
    Oregon
    I have a Sears M42 lens I picked up on Ebay for $10. (28mm f2.8). But I am having an issue with the highlighted part of the aperture mechanism in the picture below. First, I have tried to search various places, but I don't know what is the circled part called so I get the right answer.

    And second, how so I fix it so that part can move? It sticks out a bit, and interferes with the lens seating down all the way on my adapter, and it needs to move so the aperture can operate.

    Thanks

    lensJPG_dv4z3p87n7.
     
  2. PakkyT

    PakkyT Mu-43 Top Veteran

    764
    Jun 20, 2015
    New England
    Auto Aperture Pin.

    I have read of some people simply moving it all the way to the side you want it on and applying a drop of superglue to hold it. However that wouldn't address the pin sticking out. Maybe you can drill a hole in the adapter for the pin to sit in?
     
  3. jdcope

    jdcope Mu-43 Regular

    92
    May 21, 2015
    Oregon
    OK, that's what I thought the spring loaded pin was called. Thanks!
     
  4. jdcope

    jdcope Mu-43 Regular

    92
    May 21, 2015
    Oregon
    Sorry, I hit send before I finished the reply. Gluing isn't really an option. That pin moves in the slot when you change the aperture, so it would need a slot in the adapter as well.
     
  5. Turbofrog

    Turbofrog Mu-43 Hall of Famer

    Mar 21, 2014
    Easiest answer would be use a file or a Dremel and simply grind down the pin so that it rests flush with the lens flange. Just make sure that none of the material "mushrooms" out so that it can no longer move freely in the slot.
     
  6. barry13

    barry13 Super Moderator; Photon Wrangler

    Mar 7, 2014
    Southern California
    Barry
    Make sure you clean up any metal shavings very well, you don't want them getting into your shutter etc.
     
    • Agree Agree x 1
  7. dwig

    dwig Mu-43 Top Veteran

    621
    Jun 26, 2010
    Key West FL
    This pin was unique to a few Sears models and their manufacturer's own branded version. It relays the set aperture to the body. It was never used on an Asahi Pentax model and therefore is not accounted for in most (all?) adapters.

    I would recommend modifying the adapter unless you are skilled in disassembling lenses. If I were to be tasked with modifying the lens, I would disassemble the mount (3 screws) and removing the pin instead of grinding/filing/milling off the pin and having issues with the filings getting into the lens. There's not much risk with a $10 lens, but filings in the lens will likely migrate into the body when it's mounted and could cause significant damage there.
     
    • Like Like x 1
  8. jdcope

    jdcope Mu-43 Regular

    92
    May 21, 2015
    Oregon
    Thanks. Removing the pin was going to be my plan. I don't want to file anything. Too scary.
    I have already taken my Helios 44 apart to clean it, so I think I can do this too.
     
  9. dwig

    dwig Mu-43 Top Veteran

    621
    Jun 26, 2010
    Key West FL
    Keep in mind that Japanese lenses often use a "lock-tight" like substance on the mount screws. Acetone (e.g. cheap rot gut nail polish remover without any skin softening additives) will usually release it. Also, they don't use Phillips screws despite the look. They use a JIS standard cross point screw which has different angles, different sized flattened "point", and different widths to the 4 vanes. It's hard to find a Phillips or Phillips-like driver in the US that fits well without out tracking down drivers that a specifically JIS spec.
     
    • Like Like x 2
  10. jdcope

    jdcope Mu-43 Regular

    92
    May 21, 2015
    Oregon
    Interesting, I had no idea.

    As it turns out, one of the screws is super tight and I stripped the head. However, it appears the pin is pretty weak metal. I was trying to see how far I could tighten it on the adapter, and it bent over pretty easily. So I gave it a light tap and over it went into the slot, far enough to clear the adapter flange. It didn't mess with anything else.

    The lens is seated completely on the adapter, and the aperture works fine now.

    Thanks for all the input!
     
    • Like Like x 2