At the time it didn't occur to me to try silver soldering -- I suppose because I thought it would give me a silver-colored joint. Also because the metal involved was rather massive, compated to what I have handled before with silver solder, which had been focused on a small point. I have successfully silver-soldered only small things like jewelry, but also a metal eye-glass frame and a broken clarinet-key. I used a boric acid solution for flux.
I have a question on your secrets, however.. I always thought the main problem was to get a high enough temperature. I have, sitting in my garage, a gadget that I have only used a couple of times -- a sort of cheap poor-man's torch they now sell in the US consisting of a small bottle of mapp gas and a small bottle of oxygen. How can I get a flame that is both hot and carbon rich? Can I use a flame with oxygen added? At 12:31 AM 12/27/98 +0000, you wrote: > >I would suggest you use jewellers' silver solder instead of brazing. This is basically silver with copper added to vary the melting point. The 'Easy' grade has the lowest melting point at between 605° and 723° Centigrade. When soldering brass some copper from the parent metal will migrate into the silver solder colouring it to a nearly invisible joint. > >Secrets of success > >1. The metal must be cleaned with an abrasive and no finger marks added to contaminate the joint. > >2. Build a 'nest' of firebrick around the job to contain and reflect the heat. > >3. Apply the appropriate flux (obtainable from the solder source - or I can give more detail) and place small pieces of solder in the flux ready to flow into the joint. > >4. Heat evenly and gently to drive off the water in the flux. If the boiling action pushes the solder pieces (pallets) away from the joint push them back into place with a steel wire. > The gas flame should contain extra carbon if possible to 'reduce' oxides formed in the joint. Instead of combining with the metal to form copper oxides it will combine with the carbon in the flame and pass off as carbon monoxide i.e. the flame will actively 'clean' the joint. A carburising/reducing flame is obtained by reducing the air or increasing the gas. > >5. Heat as quickly as possible keeping the direct flame off the solder if possible. > Prolonged heating will oxidise the joint and prevent the solder flowing. > >6. The heat of the workpiece should melt the solder which will then flow quickly into the hottest part. It can be 'pulled' into place with the flame. > >7. Once flowed do not 'cook' the joint with further heating. > >Your local library ought to have a book on beaten/hammered metalwork or silversmithing which will give more information. > >Hope this is some use. > >Tony Moss. > >
