Soldering with open flame

[Scheldeman]

Hi there,
I only recently tackled the technique of manufacturing small brass pieces and soldering them together. Since soldering with an iron doesn't really work for me (having to touch/wipe the carefully positioned workpiece and wait for the brass to heat up + little control in the amount of solder adhering) I started using a butane micro-burner to heat prepared slivers of solder placed on the joints. This seems to me a more practical way to work with miniature brass. I however have never encountered this method in books, modelling articles or video tutorials. Is it really that uncommon or are there known problems with this technique applied on small-scale? Also, are there more or less burn-proof materials to temporarily fix the brass with while soldering? I'm now using strips of painter's tape, and each pass results in a smokefest. It's fun but not very efficient at holding the piece in place.

[blw]

Sounds to me as if you were using an iron that had too little power/heat. With enough heat reserve (such as with a temperature-controlled iron) you should not have any trouble controlling the amount of molten solder. Where it goes is a matter of flux placement.

I've used a micro torch, but not on anything as small as what's typically seen in ships. Maybe the equivalent of masts or a bit smaller, but certainly nothing like PE railings or anything of the sort.

[Admhawk]

Pieces of wood and screws. 2x4 chunks or similar etc.

My experience is that it's difficult to control the heat and it is very easy to overheat causing carbon deposits that prevent the solder from adhering. It also causes previously soldered items to melt and fall apart. Still, it has its place for certain applications.

[Scheldeman]

Many thanks for your insights. Until now I used the torch for soldering yards on mast and fixing PE triangular yard-cables on this. I didn't use it yet on anything as small as railing, since I usually glue this. It's true that the brass easily overheats causing carbon deposits. I clean this off by dipping in diluted acid and rinsing. It's also true that my inability to obtain decent results with a soldering iron probably has something to do with the type and quality of the tool. I have a rather crude 10 dollar iron with pointy tip and without power control. So investing in a tool with better control could probably improve results? Also: do I have to apply solder on the tip and wipe it on the flux-treated joint, or is it better to heat the brass with a clean tip and push the solder directly against the joint? I see both methods demonstrated in tutorials so this part is a bit confusing to me.

[blw]

It's also true that my inability to obtain decent results with a soldering iron probably has something to do with the type and quality of the tool. I have a rather crude 10 dollar iron with pointy tip and without power control. So investing in a tool with better control could probably improve results?

It was apparent from the description what you'd used! Deducing how I know this is left as an exercise for the reader! Seriously, I did exactly the same thing - I was only trying to solder electrical wires to a connector, about the easiest possible soldering job. And I was basically hopeless at soldering. A few months later my boss asked me to make another cable, and I said "nah, I can't solder worth a darn" to which he responded "well get the right tool." A 40- or 75w temperature controlled iron was shortly plugged in and no joke, it seemed like magic to me! For the small kinds of stuff that we do in ship models, that's all you need. It's about a $50 investment if you buy a new one.

In model railroading, we have to solder to the track all the time. The crossties are usually plastic. It is way, WAY easier to melt the ties with a 15w iron than with a 200w iron! That's because once you touch the rail/wire with the little iron, it sucks all the heat out and distributes it, and the iron has no more to give. But it's still hot enough to melt the plastic. With a suitably sized iron - 200w surely isn't required - touch the joint and the iron will heat the everything and KEEP it hot enough to melt the solder within a second. Then let go - and the ties won't have melted yet. With brass ship parts being much smaller in general (the rail is usually a meter long), you need even less to heat the joint.

Also: do I have to apply solder on the tip and wipe it on the flux-treated joint, or is it better to heat the brass with a clean tip and push the solder directly against the joint? I see both methods demonstrated in tutorials so this part is a bit confusing to me.

I do the latter. The former method usually works best when the joint is held mechanically, such as with a third hand or a small vice.

[reigels]

I find a butane torch to be helpful for soldering larger items (1/700 brass buildings, etc.) Always a little extra satisfaction in a good soldered joint, compared to super glue!
I have had pretty good results by pre-cutting bits of solder and holding them in place with a dab of paste flux them heating the seam with a torch or iron. Flux, brass and solder all heat in the right order and capillary action draws the solder into a nice clean joint. Too little solder is better than too much for most pieces.

Some additional useful thoughts on the topic here: http://www.am-works.com/working-with-pe ... perations/

[Admhawk]

There are many variables in soldering.

Type of solder, ratios of metals, resin core or not, diameter.

Size and shape of tips, ie:how much of a heat sink is the tip and how much will transfer at the contact point.

Size of target piece.
Shape of target piece.
Material of target piece.
Cleanliness of target piece.
On and on and on....

Anyway, a variable tool is a definite must have if you are doing a lot of soldering.
A properly tinned tip in good shape is very helpful.
A fine point tip can be more precise than a wedge shaped tip, although, wedges can carry and transfer more heat, faster.
The tinning of the tip leaves a small amount of solder on it that helps in transferring the heat.
A thin piece of solder is helpful in added material if the tinned tip doesn't have enough to transfer.
A good liquid flux lightly applied helps the solder adhere and flow.
Tinning a part beforehand can help make the join faster and cleaner.
Overheating the flux, solder and tip will always cause problems.
If you sand or file a tip, you remove its plating, making it harder to use. Buy a new tip.
An alligator clip can be used to absorb heat so it doesn't flow to a nearby joint.
The metal must always be cleaned of any oils from your fingers. Isopropyl alcohol is great for cleaning before and after soldering.

[pbudzik]

I always use small pieces of solder, but there is no reason that a proper soldering Iron shouldn't work too. I generally only use a torch when I need to heat up something more substantial ...



Paul

[Scheldeman]

Excellent information! Thanks to you all for writing out the basics and personal experiences. I will get a solid piece of equipment and give it another try.

[wefalck]

I think the original post was about the problem of touching a soldering set-up and disturbing it while soldering, not so much about soldering practice as such.

The problem of soft-soldering with an open flame is that it may be too hot and burn particularly resinous fluxes before they can work. I overcame this problem by buying a hot-air 'reflow' soldering station. It allows you to preset a temperature and to heat a set-up without touching it. They are currently sold on e.g. ebay for around 25� or so.