iris pins missing

[Tim Deming]

I've fixed a few irises with this problem. Mostly large barrel lenses, where finding a replacement iris or blade would be impossible.

If you have the pins that fell out, this makes things much easier. I sanded these down a bit on the bottom, and tried to sand the iris blade a little too. then it was just some 2-ton epoxy to glue the pins back on. I've found that using extra epoxy, pooled around the pin, top and bottom, helps a lot in terms of making sure the pin is not knocked off again. In the lenses I've worked with, i.e. old ones, I've found there is a reasonable amount of play/free space where the pins slide -so the extra epoxy does not cause a problem.

If you dont have the pins, I've successfully used small metal screws, or even threaded bolts that closely fit the hole diameter. These have been left over parts from other shutters/cameras, etc. If you are lucky, you can find a small metal bolt with a head the size of the pin, with a few threads on it (cut off the rest of the bolt with a dremel) you can use to screw into the hole. I would epoxy these on as well.

as mentioned above, solder wont stick to the iris blades. Many are ceramic or plastic or paper. Steel/metal ones are treated or hardened in a way that solder wont stick. Be careful also as the iris blades are usually very brittle. I dont have equipment to press pins back into the iris blade hole and so havent tried this, but usually the hole is cracked or enlarged, so this wont work in that case, unless you use a bigger pin. Epoxy adheres well and holds up under normal use.

cheers

Tim

p.s. in case you need to, it's not too difficult to make new iris blades from thin sheet spring steel. check mcmaster-carr for this. it can be difficult to drill holes in this without special equipment.

[Michael Carter]

Two other lenses arrived in perfect shape; I think I'll sell the ones that do not function properly instead of trying to fix them myself or send them away.