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How Do I Load lead? - More How To guides
How Do I Load lead ?
Plastic body fillers have come a long way in recent years,
but there are still jobs that are best done with a good old-fashioned dose of lead.
You'll be needing : |
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12 steps to an invisible repair |
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1. As ever, the first step is to clean the
paint off a large area on either side of the
repair to be filled. The lead will only stick
if the area it is being used on is totally
clean. You will chemically clean the area
with flux, but this will not remove contaminants
such as grease, paint, rust and general grime. |
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2.
The DA sander soon strips the flat
panels back to bare metal, but there are
still traces of surface rust within the
seam that have formed since the repair
was made. Having to get the repair area
spotlessly clean is not unique to lead
loading of course, and applies equally to
plastic fillers and paint. |
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3.
A quick scrub with a wire wheel in the
angle grinder gets the crevices clean as
well as being pushed firmly into crevices
like this, capillary action from the heat
also helps to pull lead into the seam in
much the same way as braze will creep into
a join. This helps give it so much strength. |
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4.
The C-post repair is tricky in that it is
a vertical panel and it is easy to end up
with a large gob of lead on the floor
and very little on the panel. Therefore,
first practice on a horizontal piece of
scrap metal to get a feel for how the
torch (or in this case a plastic welder
hot air gun) imparts its heat. |
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5.
The gentle heat of the hot air gun
means the process is slow, but also very
controllable. With the panel tinned and
loaded with lead (see steps 6-9), you can
see when the metal is starting to go pasty
and catch it easily with a wooden paddle
to spread around the work area before it
goes liquid. |
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6.
Moving on to the repair, the first step
is to brush on a layer of solder paste
(flux) over the whole area. This both
chemically cleans the metal and lays down
a thin layer of lead. You can use a pure
flux followed by a very thin layer of
lead for this step, but getting the
lead on thinly enough is very difficult. |
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7. Next step is to heat up the solder paste until it melts across the surface of the panel, then wipe the area with a clean cloth. This removes the paste but leaves the very thin layer of lead that is necessary for subsequent applications to grip to. Wash and dry the area to clean off all acid residue. |
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8.
You are now ready to apply the lead. Most of the heat is focussed on the end of the lead stick, but you also need to keep the heat moving over the panel to keep that warm. When the stick starts to melt, push it hard onto the work piece and twist slightly to break the end, leaving a series of blobs across the panel. |
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9.
These blobs are then heated on the panel and pushed into the crevice with a wooden paddle dipped in tallow to keep it lubricated. The outer surface can be built up with more applications of the lead stick if needed, or the lead deposits moved around by heating them and pushing with the paddle. |
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10. Never use power tools to sand back lead as they will spread the dust everywhere and represent a real health hazard. It files back easily enough with a body file, but sliding this sideways can cut grooves in the solder that will need re-filling and too much pressure can also gouge the steel panel. |
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11.
It will probably take a few applications and sandings to get the finish this smooth, but the lead blends in perfectly with the metal to give an invisible join. Any lead shaved off can be collected and re-used a strip of aluminium tape folded and stuck below the repair will catch the bits as they drop. |
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12.
Hand-shape the lead using a file and coarse paper where it has pushed around the edges of the panel. Wash the area with soapy water to remove traces of flux which will remain active and promote corrosion, and use a solvent cleaner before painting to remove any tallow. |
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