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Cmaeda
Tinkerer
Username: Cmaeda
Post Number: 2
Registered: 11-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 21, 2007 - 04:53 am: | 
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I tried unsucessfully to epoxy a broken part back together, but the part cannot withstand the stress on it. The part is holding the main drive spring back, so there is a lot of stress on it. I did some research and found a silver solder paste that is supposed to be very strong. The solder is made by a company called Solder-It. Has anyone tried this? Would this work?
Thanks,
Charles |
Steve_s
Tinkerer
Username: Steve_s
Post Number: 87
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 21, 2007 - 05:59 am: |
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Silver solder can make a fairly strong joint, but it will not be as strong as the original component. What material is the part? If it is tempered steel, the heat of silver soldering will destroy its temper, and turn it into scrap anyway!
If the component is brass or mild steel, and there is room around the part for you to silver solder a reinforcing strip over one or both sides of the join, you may be able to make a good strong repair. |
Cmaeda
Tinkerer
Username: Cmaeda
Post Number: 3
Registered: 11-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 21, 2007 - 02:55 pm: |
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Thanks Steve. I am not sure what material the part is. Is there a way to tell? It is part of the shutter from a Super Ikonta IV. The Solder-It website says that the silver solder paste requires only a low temperature to use (They said the heat from a lighter is enough). |
Glenn
Tinkerer
Username: Glenn
Post Number: 221
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, November 21, 2007 - 03:34 pm: |
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Sorry to disagree with Steve, but silver solder will make a joint/repair that will be almost as strong as the original component - in most cases. I have built over 40 model locomotive and traction engine boilers over the years, all silver soldered and still passing their hydraulic pressure tests.I have also fabricated many steel components using silver solders. These comments refer to 'hard' solders - melting at 500/800 deg C and above, not the various silver containing soft solders that have become available.
The silver solder pastes that are available work very well, if you remember the basic requirements-
1, All pieces must be completely clean and degreased
2, Silver solder does not have good gap filling properties. The thinner the joint line, the stronger the repair will be.
3, Always use plenty of heat, so that the base metal gets hot quickly. A quick heating cycle will prevent the flux degrading.
For the best results you should try and hold the pieces together in a metal jig or by binding with iron wire.
Silver solder in rod/wire/ribbon form is available in various grades - the grades have different melting points. Here in the UK, the paste that is readily available is made from the lowest temperature grade solder. The paste is formulated for small, delicate soldering jobs/repairs.
Just remember to properly clean - remember that some 'plated' finishes can absorb oil, soak in very hot washing soda, and use enough heat for the job. You should be able to join the two pieces without the need for any strengthening pieces. |
Lucas
Tinkerer
Username: Lucas
Post Number: 44
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 22, 2007 - 06:44 am: |
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Glenn is on the money. About ten years ago I did some testing on silver soldered joints and in most cases the construction, the steel, would fail before the silver soldered joint would.
The size of the seam must not be more than 0,05mm max,or the joint will be very weak. Castolin specifies a seam between 0.02 and 0.05 mm. The failures of the soldering joints we encountered were mainly due to too large a seam or a "cold" joint, when properly soldered the steel would shear off where the construction was at its weakest. |
Glenn
Tinkerer
Username: Glenn
Post Number: 222
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, November 22, 2007 - 07:52 pm: |
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From the description given, the Solder-It paste is not a true silver solder of the 'hard' type. If it can be melted by a lighter flame, it is one of the many soft solders that contain a percentage of silver. Whilst producing stronger joints than the common tin-man's or cored solders, the product will be absolutely useless for a repair of this nature. |
Steve_s
Tinkerer
Username: Steve_s
Post Number: 88
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 23, 2007 - 05:08 am: |
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I'll admit I've never done any tests on a silver-soldered repair but I would have thought that although a repair might be adequately strong if stresses are not too high, by definition it will be quite a bit weaker than an unbroken part, particularly if bending forces are involved, unless there is some reinforcement, even if it is only a bridge of silver-solder across the join.
The only silver-solder I have used is the wire type with a separate flux. It requires heating to a bright red to run. My pop-up toaster is a 1970s Morphy-Richards model, and whenever an element fails I simply repair it with silver-solder! Anyone interested in a Classic Toaster Repair Forum?
Getting back on topic, to find out if the material is steel, Cmaeda, just use a magnet. Any variety of steel which might have been used in your camera would be attracted by a magnet. It may not be so easy to say for sure whether it is tempered, though. What colour is the part?
Is it a complicated part? I am wondering if making a replacement might be a better option than repair. |
Cmaeda
Tinkerer
Username: Cmaeda
Post Number: 4
Registered: 11-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 23, 2007 - 01:37 pm: |
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Wow! Thanks for the great replies!
Glenn-Hmm, I will have to look for some other product besides Solder-It then.
Steve_s-I will try the magnet and see what it is. The part is a pretty small. It comes from the shutter of a Super Ikonta IV (It is a Synchro Compur shutter). The part is shiny and it broke by snapping in half. It was as if the part doesn't bend, but breaks when too much pressure is put on it.
How would you make a replacement part? Is there a tutorial somewhere? That sounds like a fun project! |
Glenn
Tinkerer
Username: Glenn
Post Number: 223
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, November 23, 2007 - 06:16 pm: |
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As Lucas confirms; a properly prepared silver soldered joint will be stronger than the base material - the proviso being that the base material is of small/thin section. On thicker materials, the overall strength of the joint is also very dependent on the actual area of the soldered joint.
Many small parts are made from steel stampings, any bends in the part being done in the stamping die. Whilst you can cut/file and bend a replacement from a suitable piece of steel sheet. The easiest and most successful way of producing a part that lasts, is to file it to shape from a piece of suitably sized silver steel bar. With a good set of files this can be done quite quickly, and the silver steel part can be then hardened and tempered.
Now I must admit making replacement parts is second nature to me - I have a well equipped workshop. To anybody not set up with the facilities, buying a 'parts/scrap camera' may well be the cheaper option. |
Steve_s
Tinkerer
Username: Steve_s
Post Number: 89
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, November 24, 2007 - 04:59 am: |
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I'm obviously outnumbered here, and I hate to disagree with people whose help I will probably need myself tomorrow, so perhaps we should agree to disagree on the silver-soldered repair versus unbroken strength issue! I wonder, though, if any of the tests you did, Lucas, were on this sort of repair job, which I am assuming is a butt join in a flat piece of metal with rough jagged edges at the break?
As Glenn says, Cmaeda, unless you have at least basic workshop facilities, making a part really isn't an option, though you might have to wait a long time for a suitable "spares" Super Ikonta to turn up. Is the broken part an internal part of the shutter which might be common to all Synchro Compur shutters? If so you might have better luck, though unfortunately Compurs tend to be on the more expensive cameras, which people are less inclined to scrap! |
Lucas
Tinkerer
Username: Lucas
Post Number: 46
Registered: 07-2006
Rating: N/A
Votes: 0 (Vote!) | | Posted on Saturday, November 24, 2007 - 09:10 am: |
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No, not repairs, testing was on production work.
Silver soldered joints are very good at resisting shear forces(as Glenn points out with boilers). The advantage over welding is that there is no diffusion zone where the steel loses its properties as it basicaly gets burnt as you weld it. It also enables you to join materials of different properties which can be difficult to do by welding.
When pulling at 90 degrees angle to the soldered joint failure happens fairly quickly, but when the force is in the direction of the seam it resists often better than the base material. Silversoldering is also very good for fusing ferro to non ferro metals.
For repair I usualy add a new piece to the broken part so I can make a Z or S form seam which withstands almost all forces in all directions and file/fit the least complicated part of the piece to be repaired.
Silversoldering/brazing is a technology for people familiar with it, good results come with experience and doing the work often. |
Cmaeda
Tinkerer
Username: Cmaeda
Post Number: 5
Registered: 11-2007
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, November 26, 2007 - 11:01 am: |
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It looks like quite a discussion here. Hmm, so making a part seems out of reach for me. I saw someone online selling these shutters for $40 each (www.in-fotech.com), but I have never heard of this retailer. I think I will give that a go.
Steve_s: From the pictures I've seen, this part does seem common to most of the synchro compur shutters. |
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