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Learning Basic Soldering
Follow these tips and instructions on how to work with solder to
help you save time, money and effort. In this document you will find information
about:
- How to Prepare for a Soldering Job
- How to Solder Various Metals
- Soldering Flat Pieces of Metal
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FIG. 1 - File any
corrosion from the top of the soldering iron or gun.
FIG. 2 - The shape
of the tip on the soldering iron or gun is important.
FIG. 3 - Apply a thin,
even coat of solder to the tip of the soldering iron or gun. This is called
"tinning."
FIG. 4 - Keep a cleaning
pad or piece of steel wool handy for cleaning the point during soldering.
FIG. 5 - Crossed nails
in a scrap wood block make a good soldering tool holder.
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HOW TO PREPARE FOR A
SOLDERING JOB
- There are many types of soldering pencils,
guns and irons that are adequate for home use. Most home-use soldering
tools are heated electrically. There are soldering tips that can be
used with your propane torch. There is even a small refillable butane
gas-powered soldering tool.
- The proper soldering tool depends on your
project. The propane torch is for jobs requiring a high heat source
like sweating copper fittings. The gun is for soldering tasks requiring
a little more control of the amount of heat and where it is going, such
as joining wires, while the pencil is for intricate soldering jobs requiring
even less heat but more control, like circuit-board repairs.
- Before soldering with any pencil, gun
or iron, be sure the tip is thoroughly cleaned. Use a light or medium
file to remove any corrosion that is built up on the tip of the soldering
point (Fig. 1). The tip of a soldering tool should be clean at all times.
- Clean the tip after each use to eliminate
much of the need for filing the tip.
- The shape of the tip of a soldering tool
is also important. The modified chisel tip as illustrated in Fig. 2
is ideal for most soldering jobs.
- The tip of the soldering tool should be
small enough to reach into tight places but blunt enough to ensure that
heat is transmitted all the way down to the point.
- Before beginning the soldering job, apply
a thin, even coat of solder to all sides of the tip. This coating process
is referred to as "tinning" (Fig. 3). Tinning should be done
frequently while you are soldering.
- To apply an even coat of solder on all
sides of the tip of the pencil, gun or iron, hold a length of core-type
solder against the hot tip. With the solder against the tip, rotate
the soldering tool so all sides of the tip are covered evenly.
- Always be sure your soldering tool is
at maximum heat. You cannot get a proper soldering job with a pencil,
gun or iron that does not melt the solder quickly.
- Also, be sure the material you are soldering
is completely clean. Dirt, grease or any foreign matter limits the holding
power of solder. Any material to be soldered should be scraped, sanded
or treated with a soldering flux before you apply the solder.
- Always do your soldering on a flat, even
surface. For safety, it is best to work on a fireproof surface.
- A kitchen-type cleaning pad or a piece
of steel wool is a handy cleaning device for the point of your soldering
tool while you are soldering (Fig. 4). This pad or piece of steel wool
can be stapled or tacked to the work surface where you are soldering.
An occasional wipe across the cleaning pad keeps the point clean at
all times.
- Tack two crossed finish nails into a scrap
piece of wood to make an ideal holder for your soldering pencil or iron
(Fig. 5). These nails keep the pencil or iron off the flat surface,
hold it in place and keep the point of the pencil or iron clean while
you are doing the job.
- Always apply heat with the point of the
soldering tool held flat against the metal to be soldered. Do not try
to transmit heat with only the tipthe tip is for shaping or forming.
- Keep the soldering point hot at all times.
If either the solder or the metal to which the solder is applied is
not kept hot enough, you will get a poor soldering joint.
- Although solder is also sold in a solid
bar, core-type solder is most commonly used. One type of solder has
a rosin core while the other has an acid core.
- Always use a rosin-core solder (this has
a rosin flux in the center) for soldering electrical wiring and metals
like tin and copper.
- Use an acid-core solder (this has an acid
flux in the center) for soldering more difficult metals, such as galvanized
iron. When you use an acid-core solder, the surface to which the solder
is applied should be washed after each soldering to remove the corrosive
effect of the acid.
- A special type of solder is required for
soldering stainless steel.
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FIG. 6 - Thoroughly
clean all metal to be soldered.
FIG. 7 - In some cases,
you must apply extra flux.
FIG. 8 - When you
solder a coated surface, the coating must first be chipped away.
FIG. 9 - Apply a thin
layer of solder to wires that have been cleaned.
FIG. 10 - Offset splices
to avoid danger of short-outs.
FIG. 11 - A paper
cup makes a good holder when soldering wires.
FIG. 12 - Hold the
iron or gun under the wires and feed the solder from the top.
FIG. 13 - Properly
soldered joints are as strong as uncut wire.
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HOW TO SOLDER VARIOUS METALS
- It is important that all metal to be soldered is thoroughly clean. Solder
simply will not adhere to dirty or oxidized metal surfaces.
- Clean any flat surfaces which are to be soldered with steel wool, a file,
emery cloth, etc. It's important to take time to clean the surface thoroughly.
- Scrape any wire to be soldered with the back of a knife or any flat piece
of metal (Fig. 6). If the wire is extremely dirty, dip it into a flux.
Do not touch the wire with your hands after it has been cleaned. Natural
oils in the skin may cause the solder not to stick.
- Although the core of solder contains flux, additional flux may be required
on extremely difficult soldering jobs.
- Liquid flux can be brushed on the metal if required.
- You will need flux if you are soldering with bar solder, which does not
contain a core of flux.
- If solder remains on the tip of the pencil, gun or iron for any period
of time, the flux boils out and must be replaced.
- If you find it difficult to get solder to stick on galvanized metal or
any other hard-to-solder surface, add some flux (Fig. 7). This will
normally improve the sticking capacity of the solder.
- If you are attempting to solder any coated surface, such as enamelware,
you must chip away the coated area before applying the solder (Fig.
8). Solder will not stick to coated surfaces.
- When soldering electrical wire, separate the wires to be soldered and scrape
them clean (Fig. 9).
- Each section of the wire should then be "tinned" or coated with
a thin layer of solder.
- Apply this thin coating of solder by holding the wire on the hot tip of
the soldering tool and feeding the rosin-core solder from the top (Fig.
9).
- You will need a small bench vise or some other holding device to provide
a "third hand" for soldering jobs of this type.
- After the wires have been thoroughly tinned, twist them together (Fig.
10).
- After the wires have been twisted together, apply a small amount of flux
to the exposed wire to remove any oil that might have been left on the
wiring during the twisting process.
- A small paper cup makes an excellent holding device for soldering small
pieces of wire (Fig. 11).
- Make a slot in each side of the cup to hold the wire in a firm position.
Also, fill the bottom of the cup with water. This will make the cup
more stable and reduce the chances of a flame-up.
- Note in Fig. 10 that the splices in the wire are located at different positions.
This eliminates the danger of electrical shorts and lessens the amount
of buildup when the soldered spots are taped for insulation.
- When the wires have been twisted together and fluxed, they are ready for
soldering (Fig. 12).
- Hold the hot soldering tool under the joint to be soldered and feed the
solder from the top.
- Let the solder melt and run down until the joint is thoroughly covered.
- Allow the soldered joint to cool completely before applying any pressure.
After the solder cools and becomes hard, test it to make sure the soldered
joint is secure.
- Always use a rosin-core solder for soldering electrical wiring. NEVER use
an acid-flux solder for soldering electrical wire.
- Joints soldered properly should look somewhat like those illustrated in Fig. 13. A joint that is properly twisted and soldered is as strong as any uncut section of the wire.
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FIG. 14 - For a good
bond on two flat pieces of metal, apply a layer of solder along the edges.
FIG. 15 - Hold the
joint securely to prevent warping from heat.
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SOLDERING FLAT PIECES OF METAL
- You should solder most flat metals, such as copper and tin, with a
rosin-core solder. Use acid-core solder only on galvanized iron and
other hard-to-solder metals.
- To get a good bond on two pieces of flat metal, apply a thin layer of solder
to both edges (Fig. 14).
- After applying this thin layer of solder to the edges to be soldered together,
place the tinned edges one over the other and press them firmly in place
with the broad side of the hot soldering iron.
- As you apply pressure with the soldering iron, feed additional solder into
the joint from the side.
- A little experience will enable you to "sweat" the edges
and solder the two pieces of metal together easily, quickly and firmly.
- Heat that is applied to flat pieces of metal can cause the metal to warp
and bow up or down. This makes soldering difficult.
- When soldering two pieces of metal, hold them firmly in position with a
screwdriver or some other blunt object while soldering (Fig. 15).
- If you do a lot of soldering, you may find a small C-clamp or some other
permanent holding device helpful on jobs of this type.
- Knowing how to solder is helpful for many home repair jobs. The soldering
pencil, gun or iron and core-type soldering make it possible for you
to repair gutters, electrical wiring, sheet metal or almost any other
type of metal object.
- Always be sure to clean the point of the soldering tool on the cleaning
pad or steel wool before putting it away.
- An empty tin can makes an ideal holder for a hot soldering pencil or iron.
- If you do not use a tin can, be sure to lay the hot soldering pencil or iron in a safe position until it cools to prevent a fire hazard.
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Check your state and local codes before starting any project.
Follow all safety precautions. Information in this document has been furnished
by the National Retail Hardware Association (NRHA) and associated contributors.
Every effort has been made to ensure accuracy and safety. Neither NRHA, any contributor
nor the retailer can be held responsible for damages or injuries resulting from
the use of the information in this document.
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