There are cases, on odd shaped pieces, where an iron will not fit or positions are awkward and an open flame torch is required to provide the heat. Small hobby sizes are limited to only a few. Jewelers torches are quite expensive and designed more for production type work, usually they require hoses and external tanks.
Since most have adjustable flames, size should be set to the smallest suitable for work to avoid loosening other joints and overheating. Divided into two distinctly visible parts, the hottest point is just beyond the tip of the inner one. For lower temperatures, a butane pencil type will suffice; while for harder solders, welding or cutting; propane, MAP or gas-oxygen mix types may be necessary.
Caveat: Avoid use on low
temperature alloy castings often found in kits, such as lead, white metal or
"pewter". These may melt before solder temperature is reached on work
piece.
Work area should be free of flammables and objects that may be damaged by heat. A good flame proof, non heat conducting work surface is advisable. In spite of all the negative and unwarranted hype, asbestos cloth is still the best flexible shield. None of the substitutes, tried to date, proved close to satisfactory.
In most cases core solders are more difficult to use; since if not evaded, flame often melts wire solder before touching it to work. Liquid, paste fluxes and paint solders fair much better.
After carefully applying flux to pieces at joint surfaces, place them in intended position. Before applying flame, carefully locate and place all heat sinks to protect other joints. Use smallest flame necessary for good flow to reduce heat spread. Large tips and flattened fan spreaders may be used for bulky joints and sweat soldering by playing flame across surfaces. Since excess heat is easily attained, quickly remove flame, when solder flows into joint. Too much heat may boil or burn off some fluxes, leaving residue; which prevents proper flow of solder.
Since heat may remain for some time, do not disturb until thoroughly cooled. Slow cooling is best to assure proper distribution of alloy components throughout solid solution.
Gas only types have venturi heads to suck in and mix air with gas for a hotter flame. Unfortunately many heads and flames are too large for delicate work. Slightly bulky, these torches can handle many small solder jobs.
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Old 2,000 º F. butane torch.
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Later 2,000 º F. butane torch.
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2,000 º F. butane torch w/ 2 hour burn time..
Although more expensive in initial cost and gas refill; with their flexibility, these torches can handle almost any modelling chore requiring flame use.
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Microflame torch over 25 years old.
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New version Microflame torch.
CAUTION: When used with
oxygen mix, these torches can attain temperatures of about 5,000 º F,
which can melt brass at about 2,000 º F..
Mounting both a gas and an oxygen cylinder, it can also be used for welding and cutting. Mix and flame are adjustable by independent knobs with on off position, which permits, gas only, use for lower temperatures. Various tips provide a good selection of flames, from pin point to thumb size, to handle almost any small job. Adapters are available to connect hoses to full sized gas cylinders for production work.
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