AIS Nikkor 50mm f1.4 Disassembly

AIS Nikkor 50mm f1.4 Dis-assembly

Before we start, this is one lens that will require A LOT of patience to put back together correctly.  I got this lens for free and it has a lot of fungus in it.  I’ll show you how to disassemble it and give you HINT about how to put it back together.  Once you get it disassembled, putting it back together can be VERY FRUSTRATING AND TIME CONSUMING.  I advise you not to tear the thing all the way down like I did if you don’t absolutely have to.

** If you’re creative and skip some steps from the guide below,
you can separate all the elements out without taking everything off.
If separating the elements is your only goal, it is much easier! **

  • You can see the mold through the rear elements. There is more in the front ones, but lets skip showing you all that.  Start with taking out the 3 screws at the mount and pull the mount off.
  • Now, locate the 2 small Philips screws on the SIDE on the aperture ring, take them out and pull the aperture ring out.
  • There will be 2 screws on the side circled RED, take those 2 screws out and you will free up the stopper between the barrel and the elements, then the stopper can come out.  There will be 3 screws that are circled in yellow.  Taking those off should help when taking the elements out of the barrel.  After the stoppers are gone, twist the elements off the barrel. You will have 2 pieces falling out with the elements, one will be the stopper piece, the other one will be the piece that you unscrew the aperture ring from.  You unscrew the aperture ring from the part that is located on the upper right of the yellow circle in the above photo.
  • Another view after the lens elements are out. Red circle will be where the stoppers should be located.  It will look just like the aperture linkage(circled in yellow) except without the Notch. The aperture linkage goes on a tab that’s in between the brass helical and the inner piece.  Be sure to look for the tab before you put it all back together and keep the aperture linkage and stoppers separate.  Remember, it slides sideways.
  • Loosen the screw in red circle, and you can twist the whole black piece off  located in the yellow circle.  Once you do that the brass piece will come off, showing the actual lens assembly with the aperture. The rear 2 elements will also twist out at this point.
  • Alternatively, You can use the step above as STEP ONE and continue forward from here.
  • I took the rear elements off first.  (Remember, I didn’t have a manual for it, I was just trying to figure it out as I went. So, do it whichever way you want).  Now you can separate the 2 rear elements with a spanner wrench.
  • I already told you how to take the brass helical out 2 steps before. The next step is using a spanner wrench to take the front 2 elements from the aperture housing.  After that, you have to figure out a way to twist off the black plastic ring that says Nikon etc, yes it is threaded but is glued on in one spot.  After that, the front elements will separate.
  • DO NOT TOUCH ANY SCREWS OUTSIDE THE APERTURE HOUSING. That can mess up your focus/infinity. Especially the large flat-head screw, to be exact. NOTE: if you find out that your lens will focus past infinity when it is fully re-assembled, go back to that specific screw.
  • The rear elements separated.
  • And the front elements.

Now, do whatever you have to do to get it completely clean.  Go back through the steps and re-assemble until you reach the point when the lens assembly is ready to insert back into the barrel.  The following will be the ‘not-so-fun’ part of this journey that can literally take HOURS, especially considering the fact that I do not know any special tricks for this.

  • First:  Look at the barrel, put the mount back, find out which way is upright.  Make sure the DOT for the focus and aperture scales on the silver part is back on the top.  Put one screw back in that silver ring to hold it there.
  • Now:  Insert the stopper piece (not the aperture linkage) back to where I said it is supposed to go previously. Set the focus to infinity and twist the lens assembly back into the barrel.  If this is done correctly, the lens assembly will go in almost all the way so that you can put the 2 Philips screws back on the stopper, from the side, (red circle, step 3). Next, check the focus movement. It should rotate from minimal to infinity smoothly, with no brass showing at minimal distance, on the side.  If you mess it up you will see what I’m saying.

Now, hours later, I assume you’ve gotten the previous step, or you’re crying, or you’ve thrown the lens out the window.

  • Now:  You have to twist the lens back to minimum focal distance with the lens extended out.  It is time to put the aperture linkage in, with that tab from the inside (aperture assembly) fitted into the slot on the linkage.  Then the whole thing has to go in the slot on the side of the barrel (on top) for you to screw the aperture ring back on.  You might have to loosen the 3 screws on the silver ring (with the dot for aperture and focus scale) to twist the lens assembly out further (don’t twist the whole assembly out or u will be back at square 1).  Slide that linkage in there , do not hammer it.  Test the linkage and check to see if the aperture will go all the way open and closed while moving the tab left and right (if it doesn’t, that means the tab is not fitted completely inside the slot).  Then you have to turn ALL the rings (particularly, the silver one) back to where they’re supposed to be located.  Then you tighten all the screws and check the movement of the focus.  It should still go either way smoothly and stop at the correct spots.
  • Finally:  You re-assemble the aperture ring and you put the mount back on and hope it focus to infinity.  If it focuses past infinity (optically, not according to the scale), that means you must have moved that flat-head screw outside of the aperture assembly that I told you not to touch.

I know its confusing, but that’s the best I can do for now.


9 thoughts on “AIS Nikkor 50mm f1.4 Disassembly

  1. Admire your courage to do such thing to your lens! I would only do it if I had lost every hope and had more time to spend working on it. Thanks for the info shared, they can come handy!

    • I had to clean that lens out due to fungus. I continued to use that lens for another 2 years before I had to throw it in my parts box. Thanks for stopping by!

  2. Thanks from Japan. There are many information of disassembling and cleaning the front elements part, but no useful information about the helicoids in Japanese web sites. Anyway thanks again.

  3. Great tutorial. How do you disassemble the rear group? There are 3 lens in it.
    I can remove the back one as it is held with a retaining ring. But how do you get into the first 2 elements? I can see another retaining ring inside the cylinder, but cannot get to it. It looks like it is sealed.

    • I don’t have that in hand. But as far as I remember you grab a hold of it and twist, the metal piece on the outside and closer to the rear element, that will thread off.

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