Iris cleaning

Hi Guys,
I've been asked to clean an old lens for someone.

It's a Domiplan 2.8/50 automatic lens. (M42)

The glass is perfectly clear but the aperture iris sticks, and after a few "jiggles" i can get it to move - as if through treacle.

Inspection of the blades (though either front or back lens) shows what appears to be an oily film. Is this likely to be the cause. If so where's it suddenly come from?

If so what is the best course of action.

I can see how the lens comes apart and have the necessary tools (I spent many years in instrument engineering) but concerned that specialist devises night be needed to get the optics back in line if I remove these to get at the iris.

If it were my lens I'd probably bite the bullet as without cleaning it's as good as scrap anyway, but it's not and my elderly friend is not likely to change to digital and he's had the same old camera for as long as I've known him, certainly since the early 70's I think. I've never seen anything bigger than 6x4 when he's shown me what he's taken.

So any suggestions would be appreciated:-
1 Is it safe to dissemble
2 What is the best cleaning material (If I get that far) (I would normally use surgical spirits).
3 Is it likely to require re-alignment.

I think I've included everything that might be relevant

regards
Bernard

Firstly, as it's a Domiplan you have little to lose. These are commonplace on eBay, etc and rarely fetch more than £5-10 - if you were to completely destroy it then finding a replacement would be neither difficult nor expensive.

The most effective way I've found of cleaning oily blades is Fairy Liquid in warm water. Remove all the glass elements first and then hold the entire remaining assembly under water while opening and closing the diaphragm around 50-100 times - that should get everything squeaky clean. Dry with a hairdryer (you'll probably want oven gloves as the barrel will get very hot) - once dry the hot metal will have expanded making the blades stuck once more, don't worry as they'll free up again as it cools down. Once you're sure all moisture has gone replace the glass elements (give them a good clean while you're waiting).

If you re-assemble the lens in exactly the same way you took it apart then no re-alignment should be neccessary. Take photos of it as you take it apart so you have something to refer back to if that helps.

Domiplans are about as basic as camera lenses get so I'm sure it'll be a doddle.

As a quick addendum; do not attempt to take the iris blades out to clean. They are little more than foil and will bend when touched - once bent they are write offs. When these lenses were made the blades were assembled on a special jig and dropped in as a complete unit - without the special jig you have as much chance of making the iris whole again as you have rebuilding a cow from a hamburger. This is why you clean the whole aperture assembly as a complete unit.

Many of the Meyer lenses were designed intelligently; iow, a relative amateur can take them apart and put them back together again. I don't know the Domiplan but it may be that the iris will unscrew as a unit once you've unscrewed the rear cover. Once you've removed it, soak the unit in Ronsonol until clean - maybe 24 hours, but probably just a couple of hours.

The grease comes from the helical focusing which tends to leak over time. If the focus is at all stiff you could (remove the glass elements first) drop some Ronsonol between the tubes and work the focus till it becomes looser.

Ronsonol dissolves grease and oil but leaves no residue. It's perfect for old shutters (I use so much I should buy shares) just don't breathe it in (or smoke) while you are working.

One more: The blades are designed to run dry - the "oil" residue comes from the grease used on the helicoid which will deteriorate with age and run into the rest of the lens. Clean any remaining old grease from the helicoid with a tooth brush as you've got it in the bowl of soapy water - when you reassemble the lens just add a small amount of lithium grease (I use Halfords own brand) to the helicoid to give a smooth focussing action. No other lubricants are required within the lens.

So far I've managed to loosen the 3 small grub screws (Ithink its Locktite of maybe 40 years of muck) and the rear lens has dropped out. Not literally

I can now see the back of the blades - not touched them in view of previous comments.

I suspect the next stage is to separate the depth of field ring from the back secrion but I can't for the life of me see how. Is it sweated on or is it screwed-I can't shift it either way and I'm sure force isn't the way

:::

Bernard

I can't be specific as I've never tried dismantling a Domiplan, but you're right insofar as force is never the way.

As a general rule, when you get to a point where nothing else seems to come apart, turn the lens over and start from the other end. You'll probably find that once the front parts are removed you'll uncover further screws etc that will allow the rear to be disassembled.

This is another good reason to take notes and photos as you go along - it really helps avoid having any "spare parts" when you put it back together again.

Good advice - I have done it in the past and really wouldn't recommend it unless you have dexterity, patience and time in abundance! I did a Takumar 200/4 which failed to yield to being soaked in solvent. It took several hours and a couple of attempts at reassembly (the first time around they still stuck), but it did work in the end.

If you're interested in repairing lenses, I'd say that it's worth a go on a lens you can afford to write off if it doesn't work out (doesn't sound like it, in your case), otherwise it's best to leave the diaphragm mechanism intact if possible.