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)