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Canon_rf
Tinkerer
Username: Canon_rf
Post Number: 1
Registered: 07-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 20, 2012 - 11:27 am: | 
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I have a Canon Rangefinder 5cm f3.5 lens and while cleaning the glass the aperture blades fell out. Yes, I removed one too many locking rings. There are 12 blades and I know that there is some set order that I need to use when placing them back but I cannot figure it out. Help!! Thanks. |
Rick_oleson
Tinkerer
Username: Rick_oleson
Post Number: 1220
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, July 27, 2012 - 09:08 pm: |
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Each blade lies on top of the next one - this is fairly easy until you get near the end of the circle, when you have to slip each new blade under the stack of already-installed blades to get to its socket. You have to hold these down to keep them from disengaging while you slip the new one in. It's likely to take several tries to get it done.
There are 2 plates: one has a hole for each blade pivot pin, and the other has a slot that receives the pin on the opposite end of the blade. Usually, one end of the blade is flat and the other is rounded: the pin at the rounded end goes in the round hole, and the pin at the flat end goes in the slot. The easiest condition for reassembly is wide open, so that the blades nest like a donut around the opening. Make sure that the aperture ring is set to the wide open position, and that there is room for the plate to rotate to the stopped-down end of its travel. It is possible to get all of the pins into the slots, but have the plate rotated so that you don't have the full stroke of travel available. If this happens, you have to lift the plate off of the blades, rotate it to its proper position, and set it back into place again. |
Franciswhite
Tinkerer
Username: Franciswhite
Post Number: 8
Registered: 06-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, July 30, 2012 - 05:15 am: |
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I had a similar problem with my Voigtlander. I found this page to be of immense help: http://www.daniel.mitchell.name/cameras/index.php?page=diaphragm
In saying that, it took many, many times to get the blades to overlap, many more to get them into a nice shape, and surprisingly few to get the second plate on, and working correctly.
It is possible, and gets easier with every try. Good luck. |
Hollenbj
Tinkerer
Username: Hollenbj
Post Number: 74
Registered: 03-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, July 30, 2012 - 01:14 pm: |
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My sympathies go out to you. Don't drink coffee before attempting this. I know that one.
BTW, the LTM Canon 50 f3.5 is a pretty nice lens, even if it is a tad slow. At least, I think its sharper than my Canon 50f1.8. |
T6nn
Tinkerer
Username: T6nn
Post Number: 31
Registered: 06-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 31, 2012 - 04:43 am: |
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Sometimes it is useful to fix aperture blades to each other before the disassembly with a round piece of masking tape. For example in the scenario, described by Rick, where you only need to lift and reposition the moving plate. This trick works with oil-free blades only, of course. |
Marty
Tinkerer
Username: Marty
Post Number: 95
Registered: 11-2008
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, July 31, 2012 - 04:46 pm: |
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I just did this yesterday on an old 4A Folding Kodak. There were only 10 blades, and the parts were HUGE, but it was a very frustrating job. I finally hit on the "wide open" method that Rick Oleson describes, and after a number of tries, (I don't know HOW many times I dumped them all back out and started over,) I finally got it done. Once I got lucky and had the blades pretty close, I was able to hold the plates loosely together and tease the remaining loose pegs back into their holes.
I only mention this to point out that I agree with Rick, it IS easiest to position the blades in a wide open position, and to emphasize that it IS frustrating, but hang in there... You'll eventually get it back together. |
Hollenbj
Tinkerer
Username: Hollenbj
Post Number: 76
Registered: 03-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 01, 2012 - 09:24 am: |
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I'm serious about the coffee. I attempted to replace blades each morning for many days in a row (I think it was a Retina lens/shutter) and got very frustrated. I certainly tried the tape approach, and I don't recall what position (wide open or otherwise), but I think in the end I just got lucky on one attempt. Kind of like re-threading focusing helicals. The secret was doing this in the evening (no coffee). |
T6nn
Tinkerer
Username: T6nn
Post Number: 32
Registered: 06-2009
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, August 01, 2012 - 04:28 pm: |
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Hollenbj, I think the tape approach was only meant to work if you start before the disassembly. My typical procedure goes like this:
Remove the glass.
Rinse the lens barrel in lighter fluid while moving the aperture.
Dry it.
Close the aperture and tape the blades (from both sides if you will).
Remove the rotating plate (And the blades will come out as a single unit).
Clean the pivots.
Assemble.
Remove the tapes and check for any residue. |
Hollenbj
Tinkerer
Username: Hollenbj
Post Number: 77
Registered: 03-2012
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, August 02, 2012 - 11:42 am: |
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T6nn,
Brilliant. Thanks.
I'm certain I didn't tape before disassembly, but wish I had. It would have been easy enough. I think I was feeling a bit over-confident when I opened the retina shutter because my previous task (overhaul of my large format shutter with enormous aperture and shutter blades) went so well. Put me in my place.
Funny, but I'm looking at a lens disassembly right now and I'm definitely going to tape. I have an Avenon/Kobalux/?? 135/f3.2 in LTM that has a shift between the aperture ring indicator and the actual aperture closure. Might be easy, might be another epic. Stay tuned. |
Neuberger
Tinkerer
Username: Neuberger
Post Number: 69
Registered: 01-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, August 04, 2012 - 06:25 am: |
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The tape approach - tape used must not be too sticky - before and when reinstalling the blade set described here is very close to what I did (will do? you never know, you know) when I was more interested in cameras than nowadays, I am more into binos now. Usually no blades at all, but full of other quirks. |
Mareklew
Tinkerer
Username: Mareklew
Post Number: 278
Registered: 03-2010
Rating: N/A
Votes: 0 (Vote!) | | Posted on Sunday, August 12, 2012 - 08:40 am: |
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One more hint: using CLEAN white gas (test by smearing some over a mirror first and check for any oily residue after evaporation) you can make the blades sticky to help assembling them properly. Clean white gas evaporates residue-free, so you have kind of a volatile temporary glue.
Pay attention to ventilation though! Vapors can give you a major headache ;-)
Marek |
