The fitting Helios-81М 2/53 on Nikon cameras
Helios-81М 2/53 is the kit lens for cameras Kiev-19.
The lens has mount Nikon F but in spite of this, I could not put on camera my copy produced at 1981 Nikon D80. The problem is in small differences in construction. The aperture ring of Helios-84 has a skirt of 1 mm wide and this does not allow to mount the lens on Nikon. The solution is simple - to cut the skirt out.
The same problem is with lenses Helios-81Н which have a partial skirt. You can put the lens on camera but aperture ring cannot rotate. The way to solve this is the same - to cut out parts of the skirt.
Let's look at the mount of original lens Nikon Nikkor 35mm 1:2.8 Ai/s. As you can see there is no such a skirt as in Helios-81, just small lugs.
Loosen three screws and take out the back part of out Helios-81. Now we can reach the aperture ring, so we have to take it out.
Now it is easy. Take a file and grind down the skirt. The ring is made of duralumin and easily handled. It took me about 5 minutes.
At the left - the initial aperture control ring, at the right - the grind skirt.
At first, I kept tabs as on the native Nikon lens, but as it turned out the remaining part is still hampered, I grind skirt completely.
Then we set the ring into place while checking its position, checking the work of the diaphragm. If everything is well, spin the tail in place.
Now our Helios-81М 2/53 can be mounted at Nikon cameras. Auto aperture works.