aperture blade reinstall.

[jamaeolus]

I bought a barrel mount Xenotar 135mm 4.5 dirt cheap. turns out there was reasons. The coating is so degraded that it looks foggy. A problem for a different thread though. While taking apart to try to polish the optical elements the aperture blades got disrupted in their housing. Is there a good way to put them back in place? sneaky trick of some kind?

[Oldhand]

[RokkorDoctor]

Depends on the construction and to what extent they have been dislodged, but generally no easy way other than to remove the aperture assembly, realign all the blades, and re-insert the whole aperture assembly.

Difficult the first time you do it. But as with all things: practice makes it easier, eventually it won't be much of a bother at all.

Few hints:

- don't touch the aperture blades with your fingers; skin oils and acids makes them rust
- wooden sticks (toothpicks, cocktail-sticks) are good tools for manipulation
- some aperture blade pins are hollow (small hole in the middle). A sharp-pointed cocktail-stick can be lightly pressed in there to assist handling them
- re-inserting a complete assembly into the lens can be tricky, as they are sometimes deeply recessed. Hold the assembly up on a tall cylinder whilst lowering the lens barrel down over it. Rubber name ring removal tools are useful here.
- if the aperture needs re-adjusting, you can use the f/# stop ratio and full open aperture diameter to work out required diameters. e.g f/8 aperture diameter is half the f/4 aperture diameter.
- no lubrication is needed for the blades, they are run dry. Any oil/grease-based lubrication will make them stick. If lubrication is really required, it is likely only the edges of the rotating ring that holds the aperture blades, and then only a very small amount of dry-lube such as graphite powder or molybdenum disulfide powder.

Oldhand is correct: the blades are laid down overlapping one on top the other, the last one needs to be manipulated back underneath the first one.

Good luck!

EDIT: corrected a few minor typos

[Himself]

Very difficult as a level. And I'm handy. At least I like to think that way
I put a dowel through the barrel where the blades sit. If it's smaller shim it with some gaffer's tape. But it doesn't have to wobble. It has to stick out around 1/2" give or take. I used dental picks and a long thin screwdriver with a magnetized tip. It was a long barrel. 135mm lens.
Blades are to be installed, given that I put the dowel through the barrel, wide open.
Second blade goes UNDER the first one, 3rd UNDER the 2nd, etc.

[jamaeolus]

Yeah I'm aware of the last blades going under. It has lots of blades. I am in for a serious challenge as I am cursed with poor dexterity compounded with an age tremor.

[Mir]

[Ernst Dinkla]

Bought a Petri 7 compact camera with a Petri 4.5cm 1.8. Dead on more aspects. It was the lens I was interested in, but its 8 blades diaphragm was damaged, not just blades loose. Bended some to their original shape, with scissors cut away corners that could not be reshaped but did not affect the opening itself, reassembled with the blades in a different order that could work. Then soaked the assembly in lighter fluid to get rid of any fat that might have gathered during the job. Works perfectly now. Its blades are not too shiny either.

[jamaeolus]

Well I did it! It took 4 tries before I came up with a technique that worked. I was having a really hard time getting the pegs of the last 3 or 4 blades to find their holes, which were hidden under the first few blades . I would get to the last one or two and it would dislodge one of the earliest. Grrrr! I needed some way to hold the initial blades pegs in their proper holes while I shifted the last few from side to side in search of their holes. Desperate, I tried magnets....don't! My wife suggested thread. Yeah yeah! After installing all the easy ones I wrapped thead tightly around the ring leaving open the portion of the blades I would need to slide under. A little finagling with a sharp pencil and or toothpicks I got all the pegs in their holes. Then using sharp pointy scissors i clipped all the thread. Then i mounted the sliding gear thingy with a bit of back and forth and the top pegs dropped in. Inserted the hold down ring and mounted it back in the housing. Now for the lenses.....

[jamaeolus]

[Oldhand]

Well done -
you seem to be missing two aperture blades

[Lloydy]

All good tips so far, I often use a tube to sit the lens on, usually a bit of plastic waste pipe fixed to a block of wood to keep it upright. I use pointed bamboo kebab , bbq sticks about 6 inches long - giant cocktail sticks - which are excellent for releasing the blade from the end of a magnetised screwdriver - and those cheap magnetizers are so good as they demagnatize as well.
A home made device I made when doing the multi bladed Pentacon's is this simple thing made with an rubber band, two bits of plastic ( cotton buds ) and some kind of washer thing for the bottom, mine has a rubber thing I had lying about but a bit of stiff cardboard would do the job. I use the slight tension of the rubber band and the plastic stick to hold the blades down as I place them. It works remarkably well and is easy enough to work around. Once the blades are in place I carefully lift the plastic stick with tweezers and cut the rubber band. It's important to have the least tension on the band as you can get away with.





https://www.amazon.co.uk/Silverline-245116-Magnetiser-Demagnetiser-50/dp/B000WTLOBI/ref=asc_df_B000WTLOBI/?tag=googshopuk-21&linkCode=df0&hvadid=208026936151&hvpos=&hvnetw=g&hvrand=16030588487740704726&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy=1006575&hvtargid=pla-450712522724&psc=1

[Himself]

Excellent job!
How many blades? I lost count after first 10

[jamaeolus]

It seems one maybe 2? Blades disappeared somehow. Which is truly puzzling as the whole lens has never left my desk during process.

[visualopsins]

[Dejan]

[KEO]

Congrats on getting that together. I know what a tricky job that is.

FWIW, I bought a beater Steinheil Quinar 135 a couple years ago, and the 10 aperture blades were constantly threatening to buckle when I stopped it down. I used a tiny, tiny amount of teflon grease (typically used for firearm actions) and it worked like a charm. It's been about two-and-a-half years and there's no sticking at all. They're smooth like butter.