Composition and requirements
Of body solder
Body solder consists of 68.5 per cent lead, 1.5 per
cent antimony and 30 per cent tin. The solder has
to possess the following characteristics:
1 It must remain plastic over a large temperature
range, so that it stays workable.
2 It must wipe with the solder stick and not
crumble, thus providing a clean surface finish.
3 The lead and tin must not separate, as it is
worked in vertical or overhead positions.
4 It must be capable of being reheated and
reworked without forming hard spots.
Process of body soldering
During the repairs of body damage, some means of
reproducing the normal contour of the damaged
area is necessary when it cannot be restored by
normal panel beating methods. This is a case
where body solder can be used to advantage so
the area can be filled and then dressed down to
a smooth and perfect finish.
Body soldering requirements are soldering
blocks, which are usually hardwood blocks shaped
to suit the panel being soldered; a suitable grease
or light oil which is rubbed on to the surface of
the blocks to stop them sticking to the solder,
resulting in a smoother surface finish (tallow is the
optimum substance for this purpose); a sanding
machine, files and emery cloth for cleaning purposes
prior to tinning the metal for soldering; a
welding torch or similar heating appliance which
produces a low-temperature flame (if a welding
torch is used the flame should be feathered, which
means slightly carbonizing, resulting in a soft
flame): a quantity of body solder and a suitable
tinning paste complete with a tinning brush for
ease of application; and a clean rag for rubbing off
the tinning paste. The operator must also use a
self-contained air-fed mask together with a fume
extractor for his own protection and to conform
with health and safety regulations. Before commencing
work make sure that the appropriate tools
and other materials are close to the job and within
easy reach, thus avoiding a delay during working
operations.
The first step in body soldering is to clean the
surface to be soldered to a bright metallic finish.
This can be done by using a sanding machine with
the right type of sanding disc until the area to be
soldered is cleaned to the bare metal. Any small
particles of paint which the sander will not remove
can be cleaned off by using emery paper and a file;
this precleaning is very important, as the tinning
paste will not tin the surface unless it is perfectly
clean and free from paint. Apply the tinning compound
by brushing it over the cleaned section so
that an area slightly larger than that to be soldered
368Repair of Vehicle Bodies
is covered with tinning paste. Using the welding
torch with the flame set in the carbonizing condition,
which is slightly feathered and gives a
very soft flame, heat the tinning compound until it
becomes fluid. Then with a clean rag wipe the
tinned area to spread the tinning over the cleaned
surface, making sure that every part to be soldered
is perfectly clean and completely tinned. An
important point at this stage is not to overheat
the tinning paste when tinning or the surface will
turn discoloured, usually blue, and the tinning
will be burnt; solder will not then adhere to this
surface unless it is recleaned and tinned again.
Hold the welding torch in one hand and a stick of
body solder in the other and play the flame over the
tinned section, heating it just sufficiently to cause
the tinning to begin to flow. Whilst doing this, hold
the stick of body solder near the work and apply the
flame over both the tinned area and the solder stick
so that the melting stage of each coincides. When
the end of the solder stick begins to melt, press it
against the tinned section, thus causing a quantity
of body solder to adhere to the tinned surface of the
work. After sufficient solder has been deposited on
the surface of the work, select a suitably shaped
solder block, which should have previously been
greased or dipped in oil or tallow, and commence to
push the body solder over the damaged section of
the panel. From time to time the flame should be
played over the solder to keep it in a plastic or movable
state; then, using the solder block, the solder
should be moulded to the general contour of the
panel. The solder blocks must be kept continually
coated with oil or grease to allow them to slide over
the surface of the solder without sticking and picking
up pieces of solder whilst it is in the plastic
state. This coating also produces a very smooth surface
on the face of the area being soldered. It is
very important to make sure that the tinned surface
is heated to the melting point as the solder is
smeared across the area being built up; unless this
is done a poor bonding between the solder and the
panel will be the result and the solder may fall out.
After the required shape has been formed and
the solder built up to a level slightly above the
existing panel, the final finish is gained by filing
the body solder with a flexible panel file, being
careful to ensure that the level does not fall below
that of the surrounding area. After filing, the solder
can then be rubbed down with emery paper to
give a finer surface finish for painting. The sander
should never be used for dressing down the solder
except as a last resort, because it is too severe and
tends to cut deeply and unevenly into the solder.
The dust given off from the sander when using
body solder is also injurious. When the final shaping
and smoothing of the loaded area is complete
it is essential to remove all traces of soldering
flux, oils and grease which may have been used
during the loading operation. If these were not
removed they would have a harmful effect when
the section is finally spray painted.
Figure 13.43a–f illustrates the stages of body
soldering.
Safety points
1 Avoid skin contact with fluxes.
2 Use applicators of some form when necessary.
3 Do not inhale fumes from heat/flux application.
4 The use of sanding machine in finishing produces
injurious lead dust.
5 Health and safety regulations demand protection
for the operator in the form of a selfcontained
air-fed mask.
6 A fume extractor reduces the risk of adjacent
working areas being contaminated and protects
the operator.
13.12 Chemically hardening fillers
(plastic fillers)
Although body soldering still provides the best
quality of filling for a repair, there are cases where
an alternative method is required. Much research
on this matter has led to the development of plastic
fillers which would come up to the standard of
body solder. These fillers are used in the body
repair trade as an alternative method to body
soldering. They are based on the polyester group
of thermo-setting resins, and require a catalyst or
activator to cure them. Therefore the fillers obtainable
are of a duo-pack type containing paste and
hardener. When they are mixed together a catalytic
action takes place, resulting in the filler hardening
very quickly. As this plastic filler does not require
heat during its application it has certain clear
advantages. Its use eliminates fire risk, especially
when filling next to petrol tanks or any inflammable
material. It also eliminates the problem of heat
Craft techniques and minor accident damage 369
(a)
(b)
(c)
(e)
(d)
(f)
Figure 13.43Body soldering: (a) panel
preparation (b) applying the tinning paste
(c) heating the tinning paste ready for
soldering (d) applying the solder (e) forming
the solder to shape (f) dressing and filing the
finished solder (Motor Insurance Repair
Research Centre)
370Repair of Vehicle Bodies
distortion which can occur when solder filling flat
body panels. It is cheaper than body solder and
much easier to apply. The first of these fillers
developed were released some years ago and many
disappointments were associated with their use;
problems encountered were poor bonding to panels,
too much delay in hardening and too hard to file
when dry. Several fillers now available have been
vastly improved; they will harden in as short a
period as twelve minutes provided the quantities
are correct and the two chemicals thoroughly
mixed. When hard these fillers have excellent
bonding qualities and will feather out to a fine
smooth edge. Filler materials can be dispensed
either from wall mounted, air operated filler dispensers
or from portable dispensers. These dispensers
take a 10 kg tin of polyester filler together
with a matching cartridge of benzoyl peroxide
hardener (Figure 13.44).
Portable dispensers offer the user the advantage of
being able to take the filler from repair to repair or
from workshop to paint shop. In some bodyshops it
is the normal practice to use a general-purpose filler
for the main filling operation; then once shaped and
flatted, it is surfaced with a fine filler (30 per cent
unsaturated polyester resin plus 70 per cent inert
filling material) to bring the repair up to prepaint
condition. Alternatively a body shop may require different
types of filler such as a general-purpose filler,
a glass fibre reinforced filler (with added fibreglass
strands, which provide great strength for bridging
holes and strengthening weakened areas in metal and
GRP), a fine surfacing filler (a filler with very fine
surface finish to fill fine pinholes, shallow scratches,
file marks or sanding marks) and, where repairs are
being made to galvanized panel surfaces, a filler
suitable for zinc (a filler possessing high adhesion to
coated steel surfaces). Aluminium metallic fillers are
body fillers containing aluminium. The aluminium
content makes them particularly easy to mix and
apply. Unless the body shop is very large it would
not be cost effective to have many wall mounted
dispensers, and the portable dispenser offers a viable
alternative.
The portable dispenser is operated by pushing the
handle down; the filler is then extruded together
with the correct amount of hardener for that quantity
of filler (Figure 13.45). With most fillers this is
normally 2 per cent by weight. Using a dispenser
ensures that the correct proportion is added, making
it impossible to over-catalyse the filler, and thus
eliminating or very much reducing the possibility of
spoilt paintwork. With over-catalysed filler there is a
risk, particularly with metallic paints, of the repaired
area showing through owing to the action of the
peroxide in the hardener bleaching the paint.
Another major advantage of using filler dispensers
is that the filler is kept clean and uncontaminated
from the beginning to the end of the tin because
there is no need to replace the lid every time the
filler is used. This is a feat which is commonly
accepted as impossible in most body shops owing to
the rim of the tin becoming encrusted with filler
as the applicator is cleaned off, or simply owing to
forgetfulness. In any event, even with the lid being
replaced every time the filler is used, there is exposure
to air, and therefore a tendency for the filler to
lose its styrene content and thus to become stiffer
and less spreadable.
Figure 13.44Wall mounted, air operated, filler
dispenser (Bondaglass-Voss Ltd )
Craft techniques and minor accident damage 371
The technique of repair using this plastic filler is
carried out by first roughing out the damaged area
to as near the original shape as possible, or, if the
area has been patched, by hammering the patch
down below the original level of the panel. The area
is then ground using a sander to remove all rust
and paint present. A coarse-grained sanding disc
should be used for this operation as this will
provide better adhesion for the plastic filler. Next
mix the paste with its hardener on a flat surface
using a stopping knife or flexible spatula, making
sure that the materials are mixed in accordance
with the maker’s instructions (Figure 13.46). The
filler can then be applied to the damaged area after
making sure that the surface is absolutely clean
and free from any trace of oil (Figure 13.47). If the
area to be filled up is deep, make several applications,
allowing each layer to dry before adding
more filler. After the filler is applied and allowed
to set, it can be shaped to the contour of the panel
using a plastic filler file with an abrasive paper
backing, or sanded using a sander (Figure 13.48).
Figure 13.45A portable dispenser extruding correct
amounts of filler to hardener (Bondaglass-Voss Ltd )
Figure 13.46Mixing the filler and catalyst (hardener)
on a non-porous surface (Bondaglass-Voss Ltd )
Figure 13.47Applying filler to damaged area
(Bondaglass-Voss Ltd )
372Repair of Vehicle Bodies
cars and vans, which require careful alignment
of the complete structure following any serious
impact in addition to panel damage rectification.
An essential piece of equipment for repair work
is the hydraulic body jack, which is used to push
and pull body shells and component body parts
into alignment following an accident. Blackhawk
Automotive Ltd markets a hydraulic body jack
under the name of Porto Power. A range of kits
of various sizes is available to suit the needs and
capital expenditure of various repair shops. Kits
are made up in carrying cases (Figure 13.49), on
wall-board storage, and on trolleys incorporating
a small press or in the form of a bench rack
(Figure 13.50). Attachments and fittings have been
developed to use with the body jack equipment.
The use of hydraulic body jacking equipment is
not new, nor was it invented suddenly. It has developed
to its present sophisticated state over many
years. At one time the only type of jack available
was the ratchet or screw-type body jack. The use
of hydraulic body jacking equipment developed
from the use of an ordinary hydraulic jack for
this purpose. The hydraulic hand jack had all the
advantages of providing tons of closely controlled
torque-free power for the minimum of effort by
the operator. It soon became apparent that the
hydraulic jack was ideally suited to repair work
because it could be operated in any plane and
controlled from outside the car. In the essential
repair of collision work, a large percentage of the
work will require the use of the body jack to push
or pull large areas or sections back to, approximately,
their original positions. Hydraulic body
jacks can be extended to any desired length by
incorporating a number of attachments which are
available for pushing or pulling.
The outer skin, or panels, of a body is made
from light-gauge metal, placed over a framework
of heavier, stiffened metal which is reinforced with
various types of supports and braces. In addition
to damage as a result of a collision to the outer
panels of the body, the inner construction which
is attached to the outer panels also becomes damaged,
which means that the surface of the outer
panel is prevented from being restored to its original
contour; hence the inner construction must be
restored to its original shape and position either
before or at the same time as the outer panel metal
is corrected. In some instances it will be found that
Figure 13.48Shaping panel contour with abrasive
paper and backing block (Bondaglass-Voss Ltd )
Plastic filler should never be used over rusted
areas without patching the area with new metal so
that the filler is applied to a solid base. It should
not be used in areas on a panel or body surface
which are continually in direct contact with water.
Never drill holes in a panel to give the filler a
better grip, as the holes will allow water or dampness
to work in between the filler and the metal
surface, leading eventually to the separation of
filler from the metal surface. The filler should
not be applied in any great thickness, especially
where excessive vibration occurs, or the surface
will crack and fall out. A good standard of finish
can be achieved using these plastic fillers if the
correct working procedure is adopted.
13.13 Body jack (hydraulic)