Silver soldering stainless steel

Anonymous-0

Well-known Member
In rebuilding some small engine carbs., I've machined replacement throttle shafts of 303 SS and would like to silver solder the linkage to the end of the shaft. I have not been sucessful at this using a Prestolite torch, any suggestions?

Thanks in advance.
 
we always use a small oxy/acetylene flame for silver solder, I don't think a fuel only flame will get hot enough. Silver solder is good stuff though, for certain jobs. 2cents..

Garry
 
Randy and Garry, I understand MAPP gas is quite a bit hotter than propane. Would this work? I understand what you are saying about the oxygen though. Just curious.
 
A Presto-lite torch is air/acetylene and the hottest flame of any fuel gas with either straight air or oxygen. Commonly used by plumbers cause it heats faster than propane. Might need an oxy/acet. set up to get a little more heat but I think you use a reducing flame(excess acetylene with a longer feather) for silver soldering. It's not the hottest flame but still hotter than with air/acet. Maybe you just need a bigger tip for your Presto-lite torch?
 
(quoted from post at 19:30:48 02/24/13) In rebuilding some small engine carbs., I've machined replacement throttle shafts of 303 SS and would like to silver solder the linkage to the end of the shaft. I have not been sucessful at this using a Prestolite torch, any suggestions?

Thanks in advance.
Oxy acetylene is preferable for this particular job for two reasons, 1) it is the hottest and quickest heat available. 2) the heat can be concentrated in a smaller area. Your Mapp or Propane has such a wide soft flame that the sheer force of the flame makes it difficult to perform your task on such a small item.

If you are fortunate to own or can borrow the small carry around oxy/acet torch set that HVAC service techs use the small sized mixer and torch tip makes it a remarkable tool for this purpose...Got any friends in air conditioning repair?

Next google LLOYD's stainless steel flux and see if you can find a local supplier. This flux is specifically for use with stainless steel connections and is much superior to the other fluxes that are used for normal soldering work. You may only have the need for it once every ten years, but it is worth it when you need it.

Sorry for the length of the reply. Good luck.
 
There are several grades of silver solder also. Depending on the silver content.Make sure you get one that is forulated for stainless and the right flux is imperative.
 
(quoted from post at 05:31:51 02/25/13) There are several grades of silver solder also. Depending on the silver content.Make sure you get one that is forulated for stainless and the right flux is imperative.
Whoops, I forgot about the different solders:
Staybrite 8 is an 8% silverbearing soft solder whose melting point is really low, low enough for Mapp or Propane or Acetylene only (Prestolite), but not a good choice for this application. It comes in a roll.

Stay-silv makes a 6% or 15% silver solder, but it will be difficult to make a steel bond, but if you try it, make sure you use the Harris white paste flux only. These come in sticks, one pound to the pack.

What I use for this application is 45% or 56% silver that is sold by the troy ounce and should be available at the local air conditioning supply house. Locally, 45% currently costs $31.60 per troy ounce. This comes in a coil, usually in a hard plastic case. The Harris white paste flux would be the one to use with this product. Good Luck.
 
We used silver solder that had the flux attached to eack stick. You had to watch so the flux didn't get on any threads. We also tested foreign vehicles and we used silver solder to weld our pipe fittings to their fittings. You need an acetylene torch and make sure you clean the surfaces of each piece. We used a wire buffing wheel to clean them. Hal
 

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