Here's Dr. DISEMJG's guide to iris repair:
The Problem


The cells removed from the barrel


Note the hole for the missing pivot pin in the end of the middle blade:


The pivot plate is secured by lacquer on its threads; it proved to be something of a challenge to get it out. The denatured alcohol softened the lacquer, then a torch had to be used to heat the ring to get the lacquer to let go.


Once it is all apart the alcohol is used to clean off the old lacquer and lubricant:


The blade with the missing pivot pin, showing distortion. The blades are very soft, and respond well to gentle straightening with fingertips.


The cleaned parts; there are fifteen blades:


Measuring an existing pivot pin for duplication:


Cutting the replacement:


Measuring the major diameter of the replacement pin; the next step cuts a shoulder so the pin will fit the hole in the blade, leaving a tiny head to be peened over:


Cutting off the part:


The replacement pin and the blade that will receive it. Note the shoulder on the right end of the pin; that is the part that fits the hole, and will be peened over.


Checking the fit of the pin in the cam plate:




Preparing to peen the end of the pin; the ruler raises the other end of the blade so it is parallel with the anvil.


The replacement pin, riveted in place:


The pin, darkened with a touch of aluminum blackening solution so it will blend in:


Ready for reassembly. This is the part of repairing diaphragms that I detest. The first nine blades go in easy, the last six have to be slid under the growing stack. Everything wants to come apart at this stage; you can see some tools used to hold down the already installed blades. With most designs this step is done INSIDE the lens; the pivot plate does not come out, and the reassembly is done inside the lens barrel. That is really nasty, with hopeless access problems. This design, with both the pivot plate and the cam plate coming out of the lens, is actually quite easy.










The assembled diaphragm. Nothing is holding it together, and it has to be screwed into the back of the lens without allowing it to come apart.


The assembly held inside by two fingers, being screwed into the lens:


Seated into its channel in the barrel, mated to the aperture ring, and tested for its proper range of motion:


The pivot plate, lacquered in place once the adjustments are complete:


The repaired lens:


Makes you want to try it yourself, huh?

Now THAT is beautiful work. Congratulations on your skill and more particularly...your incredible patience!

Cheers,
Bruce

Brilliant stuff!!! I have a medium format lens that I need to overhaul the diaphragm on it. Plus... I am thinking of making a new diaphragm for the 5" f2 that I just received. With a metal lathe and abit of Yankee ingenuity, most anything can be fix or made.

Well done!

Thanks for the compliments. Barrel lenses like this are generally easy to work on; I've done identical repairs on old Zeiss Tessars. Note that while the original pins were brass, I chose aluminum. I could have made the replacement pin of either metal, but the aluminum is softer and responded better to the peening process. Wear is really not a factor in this instance.

On more complex lenses (such as that medium format lens Lynn has) getting to the diaphragm to fix it is commonly a significant problem. It all depends on the design of the lens, and some are beyond practical help.

Lynn, what kind of 5" f2 do you have? If you have one blade that can serve as a template, you can fabricate the other blades. Expect THAT to be a tedious process!

Thanks again to Les for posting my photos.

John

Good job! I've had to fix quite a few irises. Not quite as fiddly as having to machine a new backside for a Copal 1 shutter, though. I'm glad you were able to save that lens. The Kodak Anastigmat is still a fine lens, in it's own right.