MTFCA Forum

I have always had trouble soldering, making a rough, lumpy mess of it, if I can get it to stick at all. Maybe I am not the only one. Can we have a discussion by folks who have mastered this art, on the types of solder, what sticks to what types of metal and how to successfully solder with soldering guns, soldering irons, flux and resin core solder? Thank you. Jim Patrick

For many years I was disgusted as one soldering gun after another reached the point of Not Enough Heat, no matter how tight I turned the screws. Then I learned about the butane micro-torch. Much better, and I can use it to melt the butter on my oatmeal.

Absolute cleanliness is essential. Tinning surfaces to be joined prior to joining helps. Then you need a heat source capable of reaching and maintaining enough heat to heat the components as well as the solder. It is a great help if you can tilt the job so that the solder will run the way you want it to.
Others will have additional tips.

Allan from down under.

Hi James,
Acid core is for radiators and sheet metal. Solid will need acid or flux. Resin core is for electrical. Cleanliness is next to Godliness. You
can over heat but most of the time the issue is not enough heat. Good solder joints are shiny bad are not. Practice makes perfect.
Honey comb radiators should be taken to a professional if you can find one. A Weller soldering gun will probably not do starter &
generator connections with out luck & practice. You cant have to many soldering irons or small torch tips.
Craig.

Work should be spotless, clean from grease, oxidation , fit between parts should be as tight as you can get it. Use the apropriate acid or flux for the materials to be soldered. Use a solering iron of enough size or a big enough flame to supply the needed heat. Not enough heat will not flow the solder properly and draw it into the seam leading to a weak bond. Too much heat wil lead to oxidation of the materials before the solder can cover the surfaces to be joined.
There are several kinds of solder with differing melting temperatures which can be used to prevent older work from coming apart when making a repair,
The Ford workshop manual (the Ford bible) has a good chapter on soldering.

In addition to the above advice, always remember, heat the workpiece to be soldered and let the workpiece heat the solder. Do not heat the solder directly. That will only drop globs of solder on a joint that's too cool, leading to a "cold joint".

Thank you. I learned a alot and am looking forward to hearing more. I intend to type up all of the suggestions and memorize them. Is there a way of testing the temperature of a soldering gun or soldering iron to determine if it is providing the proper amount of heat. What is the proper Fahrenheit temperature? Jim Patrick

Jim

There are different fluxes for different work; steel being one of the more "difficult" metals to solder relative to brass or copper. If you are soldering steel, you will benefit greatly from "tinning butter" sold by body shop supply outlets. After tinning the part(s) with tinning butter, you need to really CLEAN the parts to remove every trace of that material as it is corrosive. Once clean, an RMA flux (Rosin, Mildly Activated) will work just fine and has no deleterious material in it to cause future corrosion. Do not buy RA flux (Rosin, Activated) as that will require cleaning...seek out RMA flux

There are different solders for different work; 60/40 solid solder being the most common and the hardest to work with. There is no flux in it, and if you want lumps, bumps, and general ugliness, this is your first choice. Why is that? It is because it takes the highest temperature to flow, and importantly has a very long (wide temperature range) plastic state before it goes liquid. This plastic state fools amateures into thinking it has "flowed" and it has in fact neither flowed nor stuck to the work in any meaningful way. For the easiest and most reliable joint while learning you want to be dealing with a eutectic solder. This means that it goes from solid to liquid almost instantly with no discernable plastic state and has the lowest melting point of all tin/lead solders at 361F. Eutectic flux-cored solder is 63/37 and is not typically sold at any hardware or big box store...you need to find it on the internet. If you're doing electrical or electronic work, this stuff is mandatory (and is purchased in a very fine gauge so as to easily control the amount used). For automotive work, you can spend the $ to buy 63/37 in larger gauge(s). Just be sure it is 63/37 with a flux core.

Absolutely avoid "non-lead" solder!!! It is difficult/impossible to work with if you have little experience and at best, is simply aggravating if you do have experience.

Soldering guns are why there are professionals. If there were no guns, you'd be forced to buy real soldering equipment and 1/2 of the pros would be thrown out of work. For automotive work like gas tanks or radiators, there are a range of wattage irons suitable for the job...American Beauty is a fine brand and makes a great product. The tip must be large enough to carry and maintain heat when applied to the part and must be kept tinned and scrupulously clean.

Here's the trick: All irons will run wild up to their maximum temperature and very quickly oxidize the tip, causing lots of maintenance of the tip during the job...so what to do? The easiest way to control an iron is to buy a "handi box", a light dimmer, a duplex outlet, a plug and some SO cord from a good hardware store. Build an extension cord that terminates into a purpose-built box with the dimmer controlling the duplex outlet and now plug the iron into this box. You can now control the heat of the iron to stay above the temp you need without running wild. It works wonderfully.

Finally, technique: Solder will flow to where there is heat; heat is applied with the iron, BUT heat will not transfer from the iron to the work unless there is a solder "bridge" between the tip and the work! Flux the part, and apply some solder to the tip of the iron and wipe off on a damp sponge. The tip should be shiny silver now. Apply some more solder to the tip of the iron and touch the work with the tip...the flux should sizzle and the solder should make a nice fillet between the tip and the work. Once it does, you can add solder into the puddle. That's it. Once you know, it will become simple work.

An example of excellent Solder: https://www.performanceaudio.com/kester ... spool.html
An example of excellent RMA flux: https://www.google.com/search?q=buy+rma ... 7972544062
An example of tinning butter: https://www.eastwood.com/ew-tinning-but ... b-jar.html

I should conclude by saying that you should do all solder work with adequate ventilation, but I recall your saying that you're an ex-marine and now clinging to steep Queen Anne tin-shingled roofs while painting, so I think that soldering is the least of your worries!

Thank you everyone. Very helpful suggestions. Thanks especially to Scott who, as always, spent a great deal of time and thought in composing his very educational response. I was hoping you would respond, Scott. Thank you. Jim Patrick

My brother has 52+ years' experience with soldering, Radiator service, as our father before us, the only soldering iron jobs would be on galvanized sheeting like fuel tanks. To get the heat in and a good flow a torch is used. This photo was when we pulled apart an axle housing, bead blasted, tinned and re-rivet, sealed with solder.

I am a Navy soldering school graduate and along with flux and cleanliness, you had to have a good mechanical connection of both soldering components, so one could not move after the heat was removed, which caused what was called a cold solder joint that did not conduct so well.

That would have been a "disturbed joint"

All else fails, read the instructions.