With soldering I have 3 rules I stick to =>

 

1-       All metal must be absolutely clean , not oxidized and must be clean and dry from oils to get the solder to stick . I use 400-600 wet and dry to get metals bare and clean .

2-       Enough heat from an iron that’s not too small or too big for the job .

3-       Flux , always use a good flux . I use Duzall ( acid flux ) for S/Steel , brg’s , arm shafts and pinions .

For steel wire , brass , copper , mild steel I use a paste flux made in England , plumbers use it , its called Fluxite soldering paste , comes in a green can and looks like grease but it's great , doesn’t cause rusting like Duzall so ya tools won’t go rusty over night .

 

Some metals just need a flux as strong as Duzall . After working with Duzall ya need to wash the work in the sink with lots of hot soapy water and a scrubbing brush as the Duzall flux keeps on “stinging” the metal even after it dries . It also causes alloy to oxidize real quick too . The Fluxite paste I mostly use is hard to get these days over here but it has some better properties than Duzall , Fluxite will stay on the joint till way after the heat has got to the hole joint where as the Duzall will all burn away before the whole joint is hot enough to allow the solder to level out so with Duzall ya need to keep applying it with a small brush until the whole joint is “set” how you want it to be and watch the fumes , they quarterize ya nose and dry out your eyes !! I hope you can find some as it really is great stuff . I’ve tried plumber supply merchants , welding supply shops and radiator shops but can’t find any . The local hardware stores used to sell it but not any more . I “tin” ( coat in solder ) the metals before I solder them together so that way all I have to do to get them to set is to apply fluxite and heat up the joint so that the solder flows , after a while ya get he knack of using gravity to help too . Tinned wire is also less likely to go rusty on ya .

 

The iron I use for most work is a temp controlled station like this one with a 1/8^th tip . 40 watts would not be warm enough , go for 50 watts minimum . 

1st I “tin” the clean metal and for big jobs where there is quite a bit of metal to heat up I use a 65watt iron similar to this old style Iron . This is the paste flux I have used for many years , very effective without any corrosion .

 

 

I use just plain lead/tin solder as used in the electronics industry .

 

To tin the wire I have a puddle of the flux paste on a plank of wood and with the big 65w iron I heat up the wire and solder in the middle of the flux puddle , turning the wire as I drag it below the iron tip with flux bubbling away all around it , that’s how the wire gets fully tinned .

I then put the same iron on a stand and once again I heat up the tinned wire and drag it through a rag to wipe off excess solder while it’s still hot , then I have wire that’s tinned to make chassis from . The same process works with stainless steel but a few drops of Duzall acid flux is required .

So it’s a combination of the 3 rules all working together - Dave