Contax MM lenses to Nikon mount instructions :

These instructions are valid for the MM lenses with narrow mount only.

First, I would take a picture of the bayonet, so it will be easy to rebuild later

Some lenses have this curved piece here, we have to remove it. This one is the Sonnar 135mm.

Now, unscrew the three upper bayonet screws. Use a good screwdriver, not those cheap ones from hobby shops, these screws are glued to the threads and it is necessary to apply a very strong pressure and turn them carefully.

And remove it.

Now, unscrew the bayonet.

Same warning here: you have to press strongly with the screwdriver to remove the cemented screws.

And lift the diaphragm ring together with the bayonet.

Caution!
Have the aperture ring in a middle position before lifting it, and lift it vertically without twisting it while lifting it, to avoid moving to the extreme side the internal iris mechanism, which could be difficult to put again in its place.

Ok, it's better to cover the lens meanwhile we are working on the ring.

Now, we have to put the bayonet apart from the ring.

When they are apart, look for the bearing ball, it should be near its place, over the small spring.

This lever will interfere with the Leitax bayonet, we have to remove it.
This lever is attached with two screws on almost all lenses.

Please look here at the other type of lever's attachment.
This is a rear view of the lever.
To be able to rebuild the lens exactly as it was, let's mark with a needle around the rear of this lever.
An now we can unscrew it.
The lever and screws are out, please save them in the provided small plastic bag
Here you can see the mark I did with the needle, now we can replace the lever exactly at the same place if ever needed.
Put the diaphragm ring on the lens, you will see a lever inside that commands the blades, which goes inside this u shaped piece of clear metal.
Now you must be able to open and close the diaphragm rotating the ring.
Put a little bit of the special grease on this small spring, so the bearing ball will get sticked to it.
Bring the small ball to its place , better don't use tweezers , the tip of your screwdriver with some  grease will not lose it,
And the ball is on the spring, leave an small amount of grease on the ball.
And this is the trick, we are not going to use the perforated steel ring , this  combined with the thinner bayonet allows the Contax lenses to focus to infinity on Nikon cameras.
So we can use several Zeiss/ Contax lenses on our Nikon and Fujifilm cameras.

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