Minolta MC W. Rokkor-HG 35/2.8: Removing and cleaning the aperture blades

Since I couldn't completely remove oil from the aperture blades of my MC 35/2.8 when installed, I tackled it thoroughly.

The aperture register with the aperture blades is removed and cleaned of oil using Zippo lighter fluid.



The candidate




Removing the optical components and removing the rear cover plate.




The filter ring is removed.




Loosen the aperture unit.




The aperture unit is off board.




The rear optical component is unscrewed.




Traces of oil on the aperture unit.






The aperture unit goes into one of the rubber cylinders for releasing decorative rings.

This means it is flat and stable.






The retaining ring for the aperture register is dismantled.




The upper holding plate for the aperture blades.




After removing the retaining plate, the aperture blades are exposed.




One slat after the other is removed.




All aperture blades are out.

The lower holding plate follows.




All parts of the aperture unit have been removed.




The remaining dismantled components in the overview.






The aperture unit is cleaned of oil in lighter fluid.

The room windows are open to let the gasoline vapors escape.




Bath in Zippo lighter fluid






Drying with the Dremel Versatip butane gas burner.

I use the hot air nozzle so that the drying does not take place directly with the flame. Otherwise there is a risk that the Zippo lighter fluid still present on the parts will burn.

It is important that there is good ventilation so that the gasoline fumes are not ignited by the Versatip.

Zippo is highly combustible and flammable, you should never forget that.




These precision tweezers are ideal for safely manipulating the aperture blades.






There is still oil hidden under the lever here.

It is removed with a cotton swab dipped in lighter fluid.




All parts, now oil-free, are ready for assembly.




This is where the pin of the lower retaining plate engages.




The aperture blades are inserted.

The pins on the lower retaining plate go through the recesses in the blades.




The last slat is inserted under the first.

All blades are inserted and aligned.






The upper holding plate comes into position ...






... and the pins on the aperture blades are aligned and fixed by the holding plate.






The control cam is responsible for opening and closing the aperture blades.




The tube into which the aperture unit is lifted.






The aperture unit is back in place and engaged.

The retaining ring for the upper retaining plate is also reinserted and screwed on.








Assembly of the optical components and the rear cover plate.

The decorative ring is the last element to be screwed in.






The cleaned aperture blades - snappy again

Only one question remains unanswered:

Where is this spring attached? And what is its function?

I couldn't find a stopping point within their radius.

The spring was also not stretched before dismantling.




A friend gave me the right clue.

Whatever the spring has to do there, it does it again. There is a recess all around the pin, the upper holding point.

I could have discovered that myself

After a not too long struggle - carried out with tweezers and probe - the spring was tamed.

I took off again the rear optical unit to have more space for this final fight


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All information provided without guarantee and use at your own risk.

There is also an easier solution to clean oil from the aperture blades. Although it is less sustainable, it requires less effort:

Nice work! I am impressed by three things here:

1. Your meticulous workmanship.
2. Your careful documentation.
3. The precision machining and metallurgy of these beautiful mid-century lenses and their mounts.

Kodachromeguy said:

Nice work! I am impressed by three things here:

1. Your meticulous workmanship.
2. Your careful documentation.
3. The precision machining and metallurgy of these beautiful mid-century lenses and their mounts.

Click to expand...

Thank you, also in the name of the Rokkor