the best solder to use is called ( stayclean silver solder ) you can get it in a welding supply store or at a home improvement center it come in a little kit .. and there is a little bottle of acid that goes with it the acid cleans the base metal ive used on my giant scale control rods for years and landing gear just clean it real good when done .. the reason it works so good its alot stronger than acid core or rosin core solder it will say stay clean on the bottle of flux. but its called stay brite solder kit

what is normally called silver solder is a high temp brazing solder about 1100 degrees! you need a gas and oxygen set to get it that hot!!! this stuff you use a propane torch or a big iron will work. just remember to clean everthing before you start with fine sand paper or steel wool then wipe it down with a solvent

good luck Jim