| Author |
Message |
    
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 15, 2004 - 05:03 am: | 
|
I finally found a replacement for the Petri Racer 1.8 which hit the ground after I finished repair. The new one arrived with a mess of aperture blades. After removal of the aperture module I found that one corner of one blade was broken off together with the guide pin.
I had soldered a new pin (made from a tiny screw) to an aperture blade earlier. The blade material is solderable after grinding off the black coating. This time it was more difficult, I had to add a patch for the broken off corner AND a pin.
First, I soldered a patch of very thin brass sheet to the corner of the blade. Then I took a very tiny countersunk screw (approx. 1.5mm diam.) and filed down the head almost completely to obtain a solderable socket. Holding the screw with tweezers I managed to solder it to the patch of brass sheet applied earlier. Of course there was a lot of solder flowing around. I carefully filed either surface of the blade so that the new corner was almost flush with the rest of the blade. Finally I cut the screw and filed down the rest to proper length (which must not exceed the thickness of the slotted disk guiding these pins).
The area around the pins will not be visible in the opening of the shutter. After reassembly of the aperture module (which was not VERY difficult, just 8 blades... the 10 blades of an old Retina were a real pain) it seems to work properly now.
It is essential that the patch (and/or the solder point of the new pin) are carefully smoothed in order not to jam the other blades. The solder point of the pin seems to be strong enough to bear the force applied by the aperture mechanism. It obviously will be different with shutter blades with broken pins, much more force is applied to the shutter blades, and a merely soldered pin probably won't stand this. |
David Nebenzahl
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 15, 2004 - 11:01 am: |
|
All I can say is, wow ...
I'm amazed you were able to patch a shutter blade with solder; aren't the blades made of tempered steel? doesn't heat ruin their temper? isn't it difficult soldering anything to steel? what kind of solder did you use?
In any case, I'd love to see some pictures of your repairs in progress. Sounds like this is the very definition of tender loving care applied to old cameras. |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, April 15, 2004 - 01:19 pm: |
|
I don't know what kind of steel aperture (or shutter) blades are made of. It seems to be some kind of 'springy steel'. The surface of many types of that kind of sheet is black or dark blueish due to oxydation during heat treatment. If this layer is scraped off I found most types of steel can be soldered. Plain steel can be soldered quite easily.
In this case I used electronic solder wire but I found that plumbers' soldering paste has a flux better suitable for metal-to-metal soldering.
I would have made a shot of the repaired aperture blade but I did not want the disassembled iris to lay around for too long. BTW there seem to be quite a few old cameras (6x9 folders etc) of which some of the aperture blades are disintegrated. It is not easy (and takes a bit of time, mostly for reassembly) to fix that but it seems far from impossible in many cases. |
Peter Wallage
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, April 16, 2004 - 01:18 pm: |
|
Congatulations, Winfried , on the success of a delicate precision piece of soldering and filing. I once hard-soldered the broken cocking lever of a Compur, but that wasn't as delicate as an iris blade. Well done!
Peter |
Winfried
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, April 17, 2004 - 03:22 am: |
|
Of course this was not the first attempt but the most successful so far. I repaired two other aperture blades but in these cases there was still a hole for the pin (in most cases they are riveted, and even if they are welded they usually leave a hole when breaking off). First time I did it I 'riveted' a countersunk screw into the hole, filed down the head and secured the new pin with superglue. On the second one I simply put in a matching screw and soldered it on the side where the pin should protrude.
Filing precisely is not so difficult. I passed one year of apprenticeship before entering engineering college, in a rather conservative company where you were supposed to be able to do everything manually they now do with mills and machines. Once you ruined a part you have been filing on for several days you learn how to do it right just the first time... |
