Guide to Silver Soldering.
Soldering as most know it when used for electrical connections etc is pretty straight forward, as long as you follow some basic rules. Make sure the wire is clean and that your soldering Iron is hot enough for the job. Also remember to heat the work….not the solder!
It can also be used as a sort of metal ‘glue’ on metal to metal joints, but most of the time this will require heat in the form of a gas gun to heat the work and let the solder run freely into the joins.
This sort of soldering is fine up to a point, but when you need something really strong, as in ‘tuber’ cages etc, then Silver Soldering is the way to go.
As in soft soldering there are rules, but they are more strict.
The work must be scrupulously clean, reasonably well fitting and you must have enough heat to bring the work almost to red hot. Even when marking the job out, use a metal scriber NOT a pencil, if there’s even a whiff of pencil there it wont work. You can silver solder steel, brass, copper or bronze, that should cover most materials for frames panels or bushings.
For tuber cages etc a standard B&Q gas gun will be fine, but things will be easier if you also have one of the smaller pencil type guns for spot heating. You can use the larger unit to bring the frame up to a good heat, then bring specific areas up to red for soldering anywhere else on the frames.
Lets say were going to join two pieces of brass rod, as in a frame or cross member of a frame:
• Dress the two edges for the best fit, rub with clean wire wool or fine emery till bright.
• Secure the pieces to be joined with wire or clamps and ensure they will not move when being worked. One of those cheap ‘Helping Hands’ type stands is ideal.
• Mix up some silver soldering paste with some clean water, this is available from where you bought your solder. Mix only a small amount, aim for a slightly thick, cream like consistency and apply to the joint with a cocktail stick, lolly stick…whatever.
• Heat the joint up gently, don’t blast it with full flame thrower mode or you will blow the paste all over the place, where the paste goes…so does the solder and you will have the nice job of rubbing back all the solder runs
• Watch for the past turning ‘glassy’, shortly after that dip the solder rod in your paste and touch the joint. It will run freely into the join….let it!
• Turn off the gas and let it all cool for a second and immerse the job on water.
• As it cools it will form a scale, this will be removed as you quench the job in the water, the remainder can be filed or rubbed off with emery.
• If you want you can ‘pickle’ the job for extra cleaning for painting etc, this is done by immersing the job a container of ‘Citric Acid’ available on request from a pharmacy. Follow the instructions and it will come out a funny pink colour, this rubs off with emery paper and leaves a good surface for primer etc.
Silver solder is available in different temperature settings, this lets you build up a structure in steps, the preceding job having used a higher heat solder than the next so it doesn’t fall off.
For a tube frame I would build the major elements using silver solder, clean it up and fill in supporting pieces with lower temperature solder.
Be aware though, that the heating of the metal affects them differently, steel will be fine and the cooling will perhaps harden it a little, copper and brass will go soft after heating, but will firm up when being worked. The vibrations of the vehicle may work harden the brass or copper but in tube frame sizes the effect should be minimal. Practice on some scrap first of course, but believe me, once learned you could pull off some amazing tube frames!
Discuss this artical here : http://www.ukrcrc.com/forum/viewtopic.php?t=4702