Switch to English Language Passer en langue française Omschakelen naar Nederlandse Taal Wechseln Sie zu deutschen Sprache Passa alla lingua italiana
Members: 70,960   Posts: 1,558,252   Online: 1016
      
Results 1 to 9 of 9
  1. #1
    zsas's Avatar
    Join Date
    May 2011
    Location
    Chicago, IL
    Shooter
    35mm RF
    Posts
    1,962
    Images
    74

    Need advice reassembeling Mamiya M645 80mm 1.9 lens

    Hi - New folk around here, but long time reader. I got myself in a situation that I need you all to weigh in. Well my lens' focus ring began to move and not actually move the lens mechanism under it. I believe the screws came loose and it was turning with nothing happening. So I turned it a bit by grasping it and the lens proceeded to unseat itself (I entered uncharted territory). I now realize that under the focus ring is the part that goes up and down and below that is the aperture settings, see below.

    I see there are three screws that need to lock the focus ring into the mechanism (it is some kind of threaded riser) and one screw to make it throw from min to infinity, and I have no idea how high it needs to be (since it goes up and down and I moved it far from where it should be) and where the three pins need to be centered at and if the spot with the two screws needs to be set - at the near or infinity? I do see three spots on the riser that look like the three screws should align to but not sure.

    Does anyone know how to put Humpty Dumpty back together again? I have tried for a few hours for no luck and now turn to my trusty friend, the internet to help. I am pretty technical so I think I can do it, but if you wish, tell me to take it in to a pro, it wont hurt my feelings. Thankfully I live in the Chicago area and International Camera is near but I think I can do it myself (maybe not??).

    I love this lens so very much and really want to get it back to life, as I love to shoot low speed film and wide open, black and white or slide usually. Stopped shooting digital and went back to my roots and have been so happy developing and scanning em myself.

    Thanks in advance for any advice. Forgive my unscientific terms, as I said before, I am not in charted territory (fixing lenses) but am one who can solder, etc, so I am pretty handy and technical, just not too sure of the names of all these parts and if you think a mortal shold attempt this?? I dont seem to be able to find a manual online for free anywhere either which doesnt help the cause...

    Lens


    Side by side:


    Focus ring left and part it sits upon


    Part focus ring sits upon


    Score mark on part focus ring sits upon - what is that?


    Part focus ring sits upon, lip with a indention where I think one of the screws goes? The score mark is a little to the left.

  2. #2
    Curt's Avatar
    Join Date
    Sep 2005
    Location
    Pacific Northwest
    Shooter
    Multi Format
    Posts
    4,553
    Images
    15
    I did this a long time back and spent hours getting it lined back up. It was hard that's all I remember about it. If you don't get it look for a camera repair shop. The 80mm on my Mamiya 645 is the sharpest of the lot, I like mine too.

    If you use a screw driver on the lens be sure not to drop it onto an element. After a while a person gets tired and anything can happen. Take your time. It screws together at the same time the connection goes together as I remember. It's tricky to do.

    Good luck,
    Curt
    Everytime I find a film or paper that I like, they discontinue it. - Paul Strand - Aperture monograph on Strand

  3. #3
    zsas's Avatar
    Join Date
    May 2011
    Location
    Chicago, IL
    Shooter
    35mm RF
    Posts
    1,962
    Images
    74
    Thanks Curt! I took another 2 hours today and just felt all the parts and such and after a bunch of adjusting, it is back together! It is not 1:1 to what the focus ring says and what reality shows (e.g., when I measure out 3 feet and lock focus on an item at 3 feet and then look at the focus ring, it says something like 5 feet - but I am OK with that, so long as the pictures come out). I figure if it is in focus in the viewfinder, then it will be in focus on the film plane - which would not be the case if rangefinder. So I think I am going to just leave it as is - run some film through it, and call it a day if it works. If it doesnt, I will have it serviced. The aperture cant stop down anymore because I missed aligning that pin up (oh well), but that is no bother to me as I shoot 99% of my shots wide open and it is locked wide open now. I have no plans on selling this rig and find my new issues *charm*, so I guess I shrug my shoulders and just move on, maybe save the money and get some chromes run through the camera & savor the fun of it and not dwell on getting this thing back to perfect state since it took me so long to just get it here at 80% state. If it gets in my way I will have to drop the cash to get it serviced. In the meantime, got my eye on an old expired lot of tungsten 160T calling my name. Wishing you happy photos too and thanks for the advice.

  4. #4
    Curt's Avatar
    Join Date
    Sep 2005
    Location
    Pacific Northwest
    Shooter
    Multi Format
    Posts
    4,553
    Images
    15
    I know they are hard to do if you aren't a lens tech., I found out once by accident and had to reassemble a Mamiya 150mm C, it took some time to get it lined up and then it slid into place. I suppose there is an easier way to do it but it's like a puzzle the first time. And I hope it's the last time I have to do it.

    Best,
    Curt
    Everytime I find a film or paper that I like, they discontinue it. - Paul Strand - Aperture monograph on Strand

  5. #5

    Join Date
    Apr 2004
    Location
    Montgomery, Il/USA
    Shooter
    Multi Format
    Posts
    5,160
    Setting focus at near distance is the wrong end to do it at. Check and set it at infinity.
    The focusing ring should be an empty tube with three screws to fix it in position, so put a ground glass at the film plane, focus at infinity and once you achieve that, set the focusing ring.

    The score mark should be aligned with the edge to it's left in the picture. That's the infinity stop and the focus ring may have a machined section that gives a "hard stop" at infinity.The fact that it's there says someone has been into the lens before, they don't come from the factory that way.

    The helical threads are called "interrupted threads" and they have as many start points as grooves. If, the focus is off by a significant amount, it's likely been assembled one thread off. If it's close enough, and works, leave it be, but at close distance it may just unscrew again.
    Heavily sedated for your protection.

  6. #6
    dehk's Avatar
    Join Date
    Aug 2010
    Location
    W Michigan
    Shooter
    Multi Format
    Posts
    887
    At infinity the lens assembly should recess all the way into the barrel, go from there.
    - Derek
    [ Insert meaningless camera listing here ]

  7. #7
    zsas's Avatar
    Join Date
    May 2011
    Location
    Chicago, IL
    Shooter
    35mm RF
    Posts
    1,962
    Images
    74
    To all the above who commented thanks so very much! I was photographing today and the focus ring slipped again (I mustn’t have tightened it enough last time I was in the lens) so I decided to have one more attempt at adjusting it before sending it to a technician. Four hours later I got it! I am so happy you all chimed in, I was given the confidence and advice to take this project on and it worked! I might blow through a full roll of film in the next 24 hours just to get it in the soup ASAP and see if I scored a 100%. Jury still out but think I got it - infinity looks spectacular and close focus was looking good - plus the lens didn’t fall off when close focused, which is key (gotta be safe)! I also was able to engage the aperture too and am now able to stop down if I ever wanted to! Gosh, I almost want to buy a beat up rangefinder now and try to bring it back to life?? I might have the bug now...it was really elegant inside that lens seeing all those gears, springs, etc...

  8. #8

    Join Date
    Apr 2004
    Location
    Montgomery, Il/USA
    Shooter
    Multi Format
    Posts
    5,160
    Don't forget the four pound machinists hammer for those stubborn screws =@)
    Heavily sedated for your protection.

  9. #9
    lxdude's Avatar
    Join Date
    Apr 2009
    Location
    Redlands, So. Calif.
    Shooter
    Multi Format
    Posts
    6,678
    Quote Originally Posted by John Koehrer View Post

    The helical threads are called "interrupted threads" and they have as many start points as grooves. If, the focus is off by a significant amount, it's likely been assembled one thread off. If it's close enough, and works, leave it be, but at close distance it may just unscrew again.
    Actually, the threads are multiple lead, multiple start threads. A regular screw thread is a single lead thread, with a single start at the end. In one revolution it advances the distance of its pitch-i.e., a screw of 1mm pitch will move 1mm for each full turn.
    In multiple lead/start threads, each start is an individual thread- e.g., in a triple lead/3 start thread viewed from the side, the fourth thread crest is part of the same start as the first. Multiple start refers to the multiple thread starting points visible when looking at the thread edge-on, while multiple lead refers to the lead distance, equal to the thread pitch of a single lead screw multiplied by the number of individual starts. A triple-lead thread of 1mm pitch will advance 3mm per revolution. It will usually have three starts and three individual threads. That's why so much linear movement can be produced by focusing helicoids of fine pitch-they have lots of starts, therefore each thread has the lead of a much coarser single-lead thread.

    It's possible for a multiple-lead thread to have fewer starts and individual threads than its lead; it will have blank area where the threads would normally be, will have less load-carrying ability, and will have to have clearance between the blank portions of mating parts. That makes possible a single thread which advances an uneven multiple; e.g., a 1.5X lead.

    An interrupted thread is something else. It is a thread which has been removed around part of its circumference, along its axis. Its mating part usually has a complementary axial segment removed, allowing them to be mated linearly to nearly full depth, then turned a portion of a turn to reach full depth.
    The late great Martin Forscher demonstrated that a screw thread camera and lens could be converted to a bayonet-action mount by interrupting the threads on a screw thread body and lens. The interrupted segments were lined up with the matching uninterrupted segments, the lens was then inserted as far as it would go, and a partial turn of the lens seated it fully. Both the body and lens had enough thread left to retain compatibility with unmodified lenses and bodies. It was particularly effective with screw thread cameras which had locks, like most Fujicas and later Mamiya/Sekors.
    Last edited by lxdude; 05-18-2011 at 01:56 AM. Click to view previous post history.
    I do use a digital device in my photographic pursuits when necessary.
    When someone rags on me for using film, I use a middle digit, upraised.



 

APUG PARTNERS EQUALLY FUNDING OUR COMMUNITY:



Contact Us  |  Support Us!  |  Advertise  |  Site Terms  |  Archive  —   Search  |  Mobile Device Access  |  RSS  |  Facebook  |  Linkedin