Help needed to access aperture blades

zahncup · Jun 19, 2015

I have a Takumar 1:3.5 200mm lens (M42 mount) that I am fond of. A couple of the aperture blades have come loose. Does anyone have any experience taking one of these apart?

David A. Goldfarb · Jun 19, 2015

Thread moved. The "Feedback" forum is just for discussion of how the APUG forum itself works, problems with the software, etc.

gone · Jun 19, 2015

I would consider buying another lens. My experience w/ putting aperture blades back on their pins has not been great (as in, it has never worked). They are very thin and flimsy, and the pins are tiny. What usually happened w/ me is that I started out w/ maybe one blade off, but ended up w/ a lot more off in trying to reattach the loose one. Opening a lens to clean or cleaning the blades on a shutter is a piece of cake. But a loose blade I don't attempt anymore.

BrianShaw · Jun 19, 2015

I don't intend to be negative, but I did that once to an enlarging lens and took a solemn oath to never do it again. I used so many curse words that I was practically forced to join the navy and may have been damned to hell.

One thing to consider is that there may be a good reason for loose blades... and it may be that the blades or pins are broken and not easily repaired.

I remember one thing, though... it is easier to replace the blades in either the open or closed position. Unfortunately I don't recall which it is.

Gerald C Koch · Jun 19, 2015

The blades are rather thin and fragile. Taking the aperture assembly apart is easy getting it back together rather difficult. You cannot handle the blades with your bare hands as the oil on the skin will screw them even more. This means working with tweezers like a watch repairman. Bend one blade even the smallest amount and the lens belongs to the dustbin. Not an easy task

The blades probably came loose because their pins were worn out. Just buy a new lens.

paul_c5x4 · Jun 19, 2015

BrianShaw said:
it may be that the blades or pins are broken and not easily repaired.

I remember one thing, though... it is easier to replace the blades in either the open or closed position. Unfortunately I don't recall which it is.

Fixing a blade or a broken pin is indeed a real pain - I have managed it with a slightly more robust lens (see: (there was a url link here which no longer exists)), but even with a half decent workshop, it is difficult.

Getting the blades seated is slightly easier in the wide open position, but you do have to be oh so careful to get all the pins located first time. Don't know how many blades the Takumar has, but the more blades it has, the progressively more difficult the job becomes.

John Koehrer · Jun 19, 2015

Wowee Zowee, Bunch of negative nellies right off the bat.

Truth:
1)It's not worth $$ to repair.
2)the blades are delicate
3)tweezers and a steady hand works.

Using x-ray vision to evaluate why they're loose doesn't work too well. The pins aren't broken. It's the left handed nut on the veeblefister.

I used to set the blade housing on a film canister and install them in the wide open position. If you sneeze, start again.
Oh! Don't install them with the blade operating ring upside down, it doesn't work.

Help needed to access aperture blades

zahncup

David A. Goldfarb

Moderator

gone

BrianShaw

Gerald C Koch

paul_c5x4

John Koehrer

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