Split-and-weld system of shaping

Metal

The introduction of welding into the panel beater’s

craft has led to the development of split-and-weld

panel beating, which is at once less laborious and

much quicker than the older methods of hollowing

and raising. The system consists of making a

pattern on a panel jig with pattern paper. The paper

is held off the jig by tension at its edge. To allow

the paper to drop on to the jig, the paper is slit

at suitable points, the edges then opening out to

let the pattern fall into position (Figure 13.12). It is

obvious, then, that additional material is required

at the slits. This may be obtained in the panel

either by stretching the metal at these points until

enough is obtained to meet the requirements, or by

welding in V-shaped pieces of metal. The final

shape is then achieved by wheeling or planishing.

Figure 13.11Standard wheel sets (Frost Auto

Restoration Techniques Ltd )

Figure 13.12Split and weld pattern

The most important points when using the

machine are:

1 The wheels must be kept clean, free from dirt

and in perfect condition.

2 The pressure exerted by the bottom wheel must

be correct for both the thickness and type of

metal being wheeled.

3 The right-shaped wheel must be used to suit the

required shape of panel.

Planishing

The technique of planishing is a very old and

established craft in the history of hand-fabricated

metal articles. Basically planishing takes over from

hollowing and raising, which shape the article, to

smooth its entire surface and finalize its shape.

Planishing can be performed in three different

ways. First, there is the technique which is used

Craft techniques and minor accident damage 349

mostly by the panel beater in planishing new work.

In this case a planishing hammer is used in

conjunction with a steel stake, both having highly

polished faces. The steel stake is mounted on a

bench and is of suitable curved shaped for the

article being planished. The work is taken to the

stake and planished over it to achieve the final

finish (Figure 13.13). Second, there is the technique

used by the body repair worker, where the

planishing hammer is used in conjunction with

a dolly block which is in fact a miniature stake

or anvil, again with polished faces. The dolly

block is held in place under the panel by hand,

while the blows are directed on to the panel surface

and transmitted through to the dolly block by the

force of the blow being in direct contact with

hammer face, work surface and surfaces of dolly

block. In this method the tools may be taken to

the job and the work carried out on the spot.

This fact makes planishing ideal for the repair of

vehicle body panels (Figure 13.14). Third, there

is the technique of planishing using the wheeling

machine as a means of smoothing the work surface

(Figure 13.15). This is accomplished by the

friction and roll action of the workpiece as it

passes between the two steel rollers. This method

is normally used by panel beaters in smoothing

and finalizing new work; it can also be used by

body repair workers, but the difficulty arises that

the panel has to be dismantled and removed from

the body shell, and is therefore an uneconomical

proposition.

Consequently planishing using hand dolly and

hammer is accepted universally as the best technique

in the repair of panel surfaces by planishing.

In some cases the three techniques can be used

together; for instance a panel can be planished

using a stake and then finished off by wheeling, or

a panel can be wheeled, fitted to the job, and then

minor rectification carried out using hand dolly

and block. All three techniques have one common

feature: when planishing the metal surface is

slightly stretched because of the metal-to-metal

contact between the working faces of the tools and

the work face of the panel. The skill in this process

lies in the fact that the craftsman has to merge,

by careful hammer blows or wheel action, all these

stretched blows into one to create a continuous

smooth surface.

Where planishing hammers are employed, the

process is carried out over a metal stake or hand

dolly. The planishing is carried out over the whole

surface of the workpiece; the blows are light and

Figure 13.14Planishing using a hammer and

dolly block

Figure 13.13Planishing using a steel stake Figure 13.15Planishing using the wheeling machine

350Repair of Vehicle Bodies

given squarely, otherwise they will produce crescent

marks difficult to eliminate. Each hammer

blow produces a flat spot, and the blows are so

directed that the spots merge imperceptibly into

one another over the whole surface. Any low

places or ‘valleys’ on the surface of the workpiece

can be eliminated by careful hammering on the

head, which slightly stretches the metal, causing it

to rise to the correct contours. Both the hammer

face and the steel stake must be kept scrupulously

clean and perfectly smooth, otherwise it will be

impossible to avoid marking the sheet. Planishing

should leave the metal with a dead smooth surface.

If this is not attained, small hammer marks can be

removed by smoothing off with emery cloth glued

to a piece of wood and used like a file.

13.3 General guide to the fabrication

of hand-made panels

When a panel is required to be made by hand, the

first essential is that a jig or former should be made

to resemble the exact line and contour. This jig

or former can be made in either wood or metal,

but preferably in wood as this is easily shaped to

double-curvature shapes. Moreover, if the panel

has to be fastened to the jig this can be done by

putting small panel pins through the metal into the

wood jig. The holes left by these tacks can be later

filled in by welding.

Once the former has been built, the next stage

is the making of the blank template, which is the

developed flat form for the total shape of the panel

being made. Some shapes can be developed using

geometric drafting methods, but where there is no

recognized method only the trial and error basis

can be used. This pattern can be made in strong

brown paper or special template paper. At this

point it is necessary to decide whether the panel

is to be made in a one-piece construction or made

in several pieces which can then be fabricated by

welding. On very complicated shapes it is sometimes

necessary to use joints; therefore the exact

location on the panel should be considered very

carefully, taking into consideration facts such as

the length of the joint, and its position in relation

to accessibility for planishing with hand tools

when assembled. Once the pattern draft has been

developed it can then be marked from the pattern

paper on to the surface of the metal from which the

panel is to be made, the two most popular metals

being aluminium and mild steel. The golden rule

of hand-made panels is that an allowance should

be made all the way round the developed size; in

other words, the developed blank should be bigger

than the pattern as it is easier to cut off surplus

metal on the finished component after shaping than

to have to weld pieces to it.

The metal blank can now be shaped by any hand

methods. Care must be taken to check continually

the shaping against the jig or former to see that no

part is overshaped. In some cases where opposing

curves meet or combine, small metal templates cut

to the correct curvature are useful to check the

relative position of individual curves as the panel is

being shaped. As each piece is completed it is tried

on the jig and made to fit it exactly by planishing.

When all the shaping has been carried out, the

next stage is to join these pieces by welding. The

only accurate method of doing this is to fasten

the appropriate pieces to the jig, making sure that

the joints are butted and not overlapped together,

leaving no gaps which may need extra welding

filler rod which leads to later difficulties in planishing.

Once the panels are secured using either

clamps or nails, the appropriate sections should

be tack welded together at intervals no larger than

19 mm. After each tack the assembly should be

cooled for two reasons; first, because the former or

jig is usually made from wood, and second, the

smaller the heat input the greater will be the

accuracy of the alignment of the job. The work is

then carefully removed from the jig, when welding

of the joints can commence. The utmost care

must be taken when welding to ensure that there is

adequate penetration, but not so much as to leave

unwanted surplus weld metal on the underside,

while reinforcement on the face side should be

slightly above the surface of the panel to allow the

weld to be completely filed off without losing its

strength. It is best to weld small sections at a time,

planishing with a hammer and dolly whilst the

weld is still hot; this allows the weld to be flattened

easily and it gives the weld inherent strength.

Once the weld is completely finished and flattened

in this manner the final finish can be obtained

by further planishing and filing which, if done

correctly, should make the weld indistinguishable

from the parent metal. The whole assembly is now

tried back on the jig and any small rectification

Craft techniques and minor accident damage 351

required is carried out by further planishing

methods (Figure 13.16). If this is then satisfactory

it is trimmed to the correct size. Any flanges, wired

edges or safe edges can then be formed either by

using hand tools or flanging jigs or a combination

of hand tools and swaging machine. The final finish

can be achieved by using different grades of emery

paper or a sanding machine with a very fine grit

sanding disc.

checks on dimensional accuracy are made during

the course of building, before the chassis frame

can be ready for the panel shop. The last of these

checks takes place on a special surface table where

random checks can be made on each part of each

chassis to enable the accuracy to be maintained

(Figure 13.17).

Figure 13.16Planishing a hand-made panel

(Autokraft Ltd )

Figure 13.17Random chassis checking on surface

table (Aston Martin Lagonda Ltd )

Aston Martin Lagonda are one of the few companies

who still specialize in producing a car which

is hand built or using traditional fabrication methods

together with press work. It was Lionel Martin,

with Robert Bamford, who began the Aston Martin

story in 1913, and he achieved a great reputation

for the standard of finish of his cars and for his

infinite attention to detail. This high standard has

constantly been maintained from those early years.

The vehicle starts with sheets of steel and various

sections of rectangular or round tubing from which

is constructed the basic chassis frame and body

structure. The choice of the thickness of sheet steel

will vary according to the load for that particular

panel. With the aid of a number of high-precision

jigs, which have to be made by specialist tool and

jig makers, construction of this first stage of the

car takes approximately three weeks. A number of

Next comes the anti-rust treatment, which involves

a thorough cleaning of the chassis frame with a

solvent, followed by hand spraying a heavy coat of

zinc-phosphate paint. The whole of the lower part of

the structure is then sprayed over with a coat of chipproof

underseal. Finally, into all the tube sections, or

any other closed areas that have been fabricated, a

wax-based preparation is injected through predrilled

holes to give protection to all these inner surfaces.

The chassis frame is now mounted on a wheeled

subframe which makes it mobile, and it is then ready

for the body shell to be fitted.

By tradition all Aston Martins have had aluminium

bodywork because aluminium is a medium

ideally suited to small production runs and for

hand building; it is also light in weight. Up to

the 1960s the whole of the body shell was built by

the company from a number of different panels, all

made with the help of a stretch-press. The angular

shape of the succeeding DBS in 1967 and the

DBSV8s in 1969 largely made this impossible, and

for the first time a number of basic rubber-pressed

panels had to be secured from an outside concern.

This practice continues today. The bought-in

352Repair of Vehicle Bodies

panels include those for front and rear wings (each

in two parts) and the roof, leaving the boot lids,

bonnets and doors to be made on site as before.

Each part of the front and rear wing will be laid

on its respective hammer former. This is an accurate

jig made of Kersite, which is a very dense and

durable material capable of withstanding a large

amount of hammering and beating into shape by

the panel beater using highly individual hand tools

(Figure 13.18) and his special skills. Following the

initial shaping, the two parts of each wing would

be welded together, ‘dressed’ or reworked to the

extent that the joint will effectively disappear ready

to be finished off, and then fitted to the now fully

treated chassis frame (Figure 13.19). This is done

by the simple means of riveting them together,

taking care to place a layer of insulation material

between the two to prevent the electrolytic reaction

that will occur between these dissimilar metals. The

rivets are similarly treated by dipping them into

an anti-corrosion compound before use. The roof,

another pre-formed panel, is similarly shaped and

is the first to be fitted.

skill and art, which has changed little in all the

years it has been practised. The bonnet is made by

taking three pieces of flat aluminium which are cut

to shape, wheeled up, then welded into one piece

and finished off by wheeling; this operation takes

almost 30 hours and is very skilled indeed. The

boot lid is made in a similar fashion. The wing

panels are fitted and the doors, boot and bonnet

are individually fitted on to their particular chassis

frame. After any rectification work, an inspection

will allow the vehicle to go forward into the

paint shop. The bonnets and boot lids will need to

be removed for the later assembly work, so these

and the doors are numbered with their particular

vehicle.

The vehicle’s progression through to the paint

process is carried out in two distinct operations,

which are longer in total than any other part of the

vehicle build. The vehicle starts with the new body

shell being cleaned down with a mild acid preparation

called deoxidine. When dried off, it is sprayed

over with a heavy epoxy-type primer surfacer and

hand rubbed before a second similar coat is applied

(Figure 13.20). Rubbed again, it is sprayed with

a base coat and then various apertures, door shuts,

screen areas and rear ends will be sprayed with

a coat of the car’s final colour. These are areas

where components will be fitted, such as front and

rear screens, door handle locks and rear lamp

assemblies, which will remain in place when the

main part of the paintwork is carried out later. The

interior of the car is sprayed over in black and is

Figure 13.18Panel beater’s hand tools (Aston Martin

Lagonda Ltd )

Figure 13.19Fitting hand-made panels (front wings

and roof) to chassis (Aston Martin Lagonda Ltd )

The doors, bonnets and boot lids have always

been hand made on site, the door skins (panels)

because they have a relatively simple shape which

can be made more economically than a rubberpressed

panel which will always have a certain

amount of wastage. The company has always made

bonnets and boot lids but these are far from simple,

and demonstrate the full range of the panel beater’s

Craft techniques and minor accident damage 353

now ready to move into the assembly area. This

begins with the laying in of various different sound

insulation panels, followed by the wiring harness

and the air conditioning unit.

The vehicle now moves forward to the area

where the suspension is fitted, for which purpose

the subframes will now have to be removed. Front

and rear suspension components are made by specialist

concerns to the company’s own design. With

all these parts assembled, and with the final drive

unit and the power steering unit in place, a set of

temporary road wheels can be fitted which make

the car mobile. Next, the preassembled engine

(which takes 60 hours to build) is fitted by hand

to the vehicle. At the end of the production line

the bonnet will rejoin the car, the underpanels and

stone guards will be fitted, and the water system,

oil and fuel will be checked.

The vehicle is then passed over to the road

test engineer who will run it for approximately

100 miles. On the satisfactory completion of the

road test, the vehicle can be made ready for its

second entry into the paint shop, but not before

its body panelling has been thoroughly inspected

for small marks or minor imperfections.

On the car’s re-entry into the paint shop, the

bodywork is masked up and then flatted by hand,

as with every part of this operation. Final colour

coating is now begun, alternatively spraying and

rubbing each coat of paint until the finishing overlay

lacquer can be applied (around 12–14 coats

of paint). This is followed by the final fit of the

vehicle’s interior trim and seats, provided in a

special colour at the request of the owner, detailed

fittings, body items and carpets (Figure 13.21). Then

after a short final road test by the same tester the

vehicle receives a final inspection (Figure 13.22)

and is passed over to the sales section.

The annual build figure for this truly hand-made

vehicle is between 250 and 300.

Figure 13.20Panelled body shell sprayed in primer

surfacer (Aston Martin Lagonda Ltd )

Figure 13.22Final vehicle inspection (Aston Martin

Lagonda Ltd )

Figure 13.21Fitting interior trim (Aston Martin

Lagonda Ltd )

13.4 Edge stiffening of sheet metal

Edge treatment is a general term used to cover

the many methods of forming the edges of sheet

metal, panels and components. The body worker

354Repair of Vehicle Bodies

frequently has to increase the strength and rigidity

of the edges of large unsupported metal panels, to

stop movement and vibration when the vehicle is in

motion and to create resistance against buckling and

twisting. This can be provided on the sheet itself or

by adding stiffening agents. The various types of

edge treatment are normally classified as follows:

Formed In this case the edge stiffening is formed

from the metal panel itself.

Applied Here the edge stiffening is made up as

a separate piece and then fixed to the panel edge.

Safe edges, flanges, wiring and swaging can all

be classed as formed edge treatments, while the

attachment of strips, half-round beads, mouldings

angle sections and false wire edges are classified as

stiffening agents. Panel edges are treated in these

ways for the following reasons:

1 To stiffen and strengthen the panel or component

at its extreme edge

2 To act as a safe edge, as it is important that

panels which are to be handled frequently

should be effectively treated to avoid the risk

of injury due to exposed raw edges

3 To ornament and decorate the panel.

Often edge treatment is used for more than one

reason; an example of this may be found on the

modern motor vehicle wing, where the edge treatment

provides a stiffening effect, gives a safe edge,

and also has the effect of being pleasing to the eye.

Folding

Folding is the simplest form of edge treatment

(Figure 13.23) and is satisfactory when neatness

and speed are the main factors. Folds may be

creased to give a flushed effect on one side of

the panel, or doubled over twice to increase the

strength. These edges can be formed either with

hand tools or with the aid of a folding machine.

Flanging

In flanging, the edge is formed at right angles inside

the panel (Figure 13.24). In addition to imparting

rigidity it can be readily cleared of road dirt, thus

reducing the possibility of corrosion from moistureretaining

matter. One disadvantage of this type of

edge treatment is that when the edge suffers a severe

blow, the metal tends to crease badly and the edge

may crack. When repairing such a fracture, care

should be taken to avoid rigidity at one point, which

often results in further cracks appearing some distance

from the repaired portion. In the case where the

edge is formed outside, a plastic moulding is clipped

over the protruding edge. Stiffening is provided by

the formed edge, the plastic moulding being used for

decoration and also to render the edge safe.

Figure 13.23Folded edges (a) single fold (b) folded

and creased edge (c) double folded edge

Figure 13.24Flanged edges

Flanging is the process of hammering the edge

of a piece of sheet metal in such a manner that the

required width of metal is worked into a position

usually at right angles to its original form. This has

the effect of strengthening the metal in the area of

the bend. It is used to advantage on panel edges

to stiffen, to make the edge safer and to improve

its appearance, and in many cases to perform the

function of a flanged joint where one metal panel

is joined to another. If the flange is on a straight

piece of metal the flanging technique can be

carried out either by using a stake and mallet and

hammering the edge over the stake to form a right

angle, or by using a bending machine which gives

a more consistent edge.

Difficulty may be experienced when forming

flanges on curved sections of panels depending on

whether the flange is on an external or an internal

curve, as these require different techniques of

working. This type of flanging can be carried out

by using a swaging machine fitted with flanging

rolls, which turns the metal edge at right angles as

it is fed through the rolls. Owing to the awkward

Craft techniques and minor accident damage 355

shape of some panels they cannot be flanged in

the swaging machine and so must be processed by

hand, using either a stake and mallet or a hand

dolly and mallet and finishing off with a planishing

hammer. If the panel is of a complicated curved

nature and requires flanges, it is sometimes necessary

to make a flanging jig of two identically

shaped pieces of wood. The panel is inserted

between the two pieces and clamped, then the

metal edge protruding is carefully hammered over.

In some cases annealing has to be carried out where

the corners are very sharp so as not to split the

metal. When taken from the jig the panel retains the

curved shape with the flange following its contour.

To form a flange around the edge of a cylinder, it

is placed against the edge of a stake so that the

width of the metal to be flanged lies on the stake.

A stretching hammer is then used to stretch the

flange metal, working the cylinder steadily round

and keeping the width of the flange constantly

on the face of the stake. The maximum amount

of stretching must take place on the outside of

the flange, gradually diminishing to nothing at

the inside. The metal must be kept flat on the top of

the steel stake, so that the hammer strikes the metal

hard on the stake top. In the case of a flange raised

around the edge of a flat disc, a mallet is used

instead of a hammer and the metal is gradually

drawn inwards or upwards by careful working round

the edge over a curved end of a steel bench stake.

By allowing the outer edge of the flange to be drawn

in slowly a good deal of creasing is avoided; moreover,

the creases which do occur around the edge

are carefully worked out as they appear. In the

working of a deep flange on a disc the metal may be

annealed at intervals except, of course, in the case of

coated metals such as tinned or galvanized steel.

Swaging

A swage is a moulding or indentation raised upon

the surface of sheet metal by means of male and

female rollers, the rollers being made in a variety

of contours. The machine to which the rollers

are attached may be driven either by hand or

electric motor, the choice of machine often being

influenced by the type or amount of work to be

undertaken. Although swaging has many similar

functions to that of wired edges, it is not confined

to edge treatment but may be used some distance

from the edge within the limits of the throat of the

machine. In addition, as no extra allowance of metal

is required, a saving in material with consequent

reduction in weight is achieved with the use of

swaging (Figure 5.19). Special composite swages

are also available for use on panels (Figure 13.25);

the rollers are made in sections so that their width

may be adjusted. If it is found that the throat of the

normal swaging machine will not accept curved

panels or wings, the rollers may be fitted on to a

wheeling machine which is virtually throatless.

The projecting shape of the swage above the surface

imparts considerable strength to sheet metal

articles. Panels which would otherwise be slack

and lacking in rigidity can be stiffened by the use

of swaging. Motor vehicle body panels are subject

Figure 13.25Common swaged edges: (a) ball

swage – may be produced in various sizes according

to the size of the wheels used; is used as a stiffener on

sheet metal (b) return curve swage – may be produced

in various sizes; is used as a stiffener in body work

(c) joggle swage – used to produce a creased lap joint

in sheet metal (d) radius swage – used to produce

radius corner joints; the small flange may be trimmed

off thus forming a butt joint

356Repair of Vehicle Bodies

to vibrations and fluctuating stresses, and for this

reason swages are used to obtain a suitably rigid

body shell. The return curve swage is frequently

used to strengthen the centre portions of cylindrical

containers because of its high resistance to externally

or internally applied forces. In addition to

strengthening purposes, swaging is often used to

relieve plain surfaces; this kind of decorative effect

is a common feature on motor vehicle bodies.

Wiring

Wiring is the process of forming a sheet metal fold

round thin wire to give extra strength to the edges

of a panel and also to improve its appearance

(Figure 13.26). The wired edge, although not so

popular as in the past, is still used where impact

strength is the most important requirement of the

edge. Mudguards on earth-moving equipment meet

conditions in service to which the wired edge lends

itself most admirably, and repairs can be readily

made, if necessary, with the aid of welding equipment.

The wired edge is still found to be a useful

form of edge treatment on the wings of public

service vehicles, particularly where the wings are

not integral with the body.

in position, and the metal is beaten over by a

mallet to hold the wire in position. The edges can

be finally closed by using a wiring hammer or

by passing through a swaging machine fitted with

wiring rolls (Figure 13.27).

Figure 13.26Wired edges: (a) plain wired edge and

(b), (c) creased wired edges

Figure 13.27Wiring process:

1 Allowance marked off and sheet folded

2 Metal beaten over wire with mallet

3 Edge closed using wiring hammer or wiring rolls

To carry out the technique of wiring, the edge of

the metal should be bent up in the folding machine

or by hand, using a mallet and stake, at the corresponding

bending line. The bend should not be too

sharp, as the metal has to be worked round the

wire. Next a length of wire is cut to size and placed

13.5 Techniques of damage rectification

Before a systematic approach to body repairs is

possible, it is necessary to understand the characteristics

of sheet metal as used for body panels.

When a flat sheet of metal is bent to a wide arc or

radius it will regain its former shape when released;

that is, it is elastic or possesses elasticity. However,

if this sheet is bent to a short arc or radius

it exceeds the limits of elasticity or flexibility; the

metal in the bend becomes stiff and will take on

a permanent set and retain the curvature. This is

the result of the stresses which have been set up

at the bend, making the material work hardened.

Before the sheet is formed in the press the grain

structure is constant and the thickness uniform

throughout (see Figure 13.28). When the metal is

Craft techniques and minor accident damage 357

formed to make the body panel it is bent beyond its

elastic limit. The outer surface stretches or lengthens

while the inner surface shrinks or shortens

(Figure 13.28). The pressure exerted on the metal

by the press also changes the grain structure

to work harden the surface layers. This build-up

of stresses in the bend or curve is an essential

factor in the design of vehicle body panels which

together form the body shell. A common feature

in the design and manufacture of a motor vehicle

is the many curved surfaces which are normally

referred to as crowns. Vehicle body panels consist

of flat or slightly curved areas, sometimes quite

large and elastic in nature (low crowns), such as

door panels; these are held in position by stiffened,

rigid sharp bends and swages which are non-elastic

in nature (high crowns), such as the cant of roof

panels (see Figure 13.29).

If a panel is damaged in an accident the buckled

area, being sharply bent, will create additional

stiffness in the panel, whether in an elastic or nonelastic

area. The slope of the buckles surrounding

the sharp creases will be fairly elastic, but a greater

amount of effort will be needed to reshape the

sections of the panel which are made rigid either

in manufacture or through accidental damage.

When a panel becomes damaged due to impact,

the resulting force on the metal causes buckling

in the form of creases or ridges which are created

because the panel has gone beyond its elastic

limits to become non-elastic, therefore establishing

unwanted rigid sections within the damaged area

on the panel. The characteristic stiffness of the

ridges prevents the panel returning to its original

shape unless additional force is applied to release

the stress in the ridges in the damaged area. When

these stresses in the unwanted rigid areas are

released, the elastic areas will also be allowed to

return to their original shape. It is important that

these corrections be made in the right sequence on

the individual panel, otherwise additional damage

will be caused to the panels. Repairs must be

Figure 13.28Change in grain structure during

pressing (Sykes-Pickavant Ltd )

Figure 13.29Prepressed wing panel

358Repair of Vehicle Bodies

performed using the reverse order and an opposing

force to that of the original force which caused the

damage. Consequently the correct sequence should

be first to remove the last ridge which was formed,

and then to work towards the first point of impact

of the damaged area.

Rectification of vehicle bodies, following a true

assessment of the damage, can be divided into two

stages: roughing out or straightening of the reinforced

sections and panels to approximately their

original shape, and the finishing or preparing of

the surface to a smooth appearance for repainting.

Both stages are of prime importance, and many

man hours can be saved if the job is processed

correctly. In cases of damage where the body is

distorted, the temptation is to use rough-and-ready

methods depending on brute force to restore some

resemblance of shape. Whilst this may speed up

the first stage of a repair, it will be found that such

methods result in additional marking of panels;

considerably more time will be spent on the final

stage of finishing than would be required if more

thought had been given to the job in the first

instance, and better methods had been used to rectify

distortion. Damaged panels should be restored

by relieving the stresses which have been set up by

the force of impact. The skill of all body repair

techniques lies in the correct handling of the basic

hand tools, in a variety of combinations best suited

for the job in hand.

13.6 Hammering techniques

Unlike most other trades, where the hammer is

used with a follow-through action from a combination

of wrist, elbow and shoulder, in the skilled

hands of a body repair worker the planishing

hammer swing is a rhythmic action involving

finger and wrist movement, producing a ringing

blow (Figure 13.30). The hammer should not be

held tensely, but during the complete cycle of

movement it should be held loosely in the hand.

This will achieve a higher degree of accuracy

and at the same time help to reduce fatigue. This

loose holding of the hammer applies equally to

dolly blocks, as it permits them to bounce back

naturally and to assume the correct position for

striking the next blow. With practice the wrist

becomes strengthened, and consequently working

in restricted places becomes easier where an even

wrist action is impossible. The dolly should be

allowed to lie naturally in the hand with the face

to be used uppermost and, as with the hammer,

should be held firmly but not tightly. Tap lightly at

the dolly to obtain the feel of metal to metal, and

check for control of force of blow; each blow will

give a metallic ring which should be the same for

each stroke of the hammer. When no metallic ring

is heard the hammer is not hitting the metal in

alignment with the dolly.

Roughing out damage

In minor repair work which can be carried out

using hand tools, the first major operation is

to reshape the damaged area back to its original

contour. This is done by a technique known as

roughing out, which must be carried out prior to

any finishing process such as direct hammering or

planishing. Roughing out is the reshaping of the

area by hand with the aid of a heavy dolly, which

forces back the damaged section to its original

shape (Figure 13.31).

When repairing collision work, the normal

method of correction is to reverse the process which

caused the original damage. In a case of minor

repair the point of impact is now the lowest part

of the damage. To reverse the process this point on

the underside of the panel should be struck using

the same force as was originally directed against it.

Figure 13.30Swing of the planishing hammer

Craft techniques and minor accident damage 359

If this spot is hit accurately with a roughing-out

dolly using the same force, the panel will spring

back almost to the contour it had prior to the

damage. In some cases you will be able to correct

the panel damage with a single blow which will

spring the panel back to its original shape. In other

cases, where the repair is larger, it will be found

that several blows are necessary. Hold the roughing-

out dolly lightly in the hand and strike the

hardest blow at the centre of what appears to be

the lowest point of the damaged area, then direct

the blows around the first one and gradually

work outwards, decreasing the force of the blows

until all the damaged area has been roughed out

(Figure 13.32). However, in most cases the damage

will not be completely restored to its original

contour, although it will be roughed out and can

be straightened to its correct contour by direct

hammering or by combination of direct hammering

and indirect hammering.

The use of a heavy hammer for roughing out

is not advisable, for this permits heavy blows

which are concentrated in small areas and invariably

results in stretching or otherwise distorting

the metal, whereas a well directed blow with

a dolly that matches the original contour of the

repair spreads the blow over a larger area, resulting

in very little distortion of the metal. In some

cases body repair workers use a boxwood mallet

for roughing out, because there is less chance of

stretching the metal. The technique is similar to

that of using a dolly, as the mallet is used on

the inside of the panel to hammer the damaged

section back to its original shape; then the work

is finished off by direct hammering using a panel

hammer and dolly. A disadvantage in using a

mallet is that on modern panel assemblies there

is insufficient space to use a mallet for roughing

out; therefore most body workers find a dolly

more useful.

Direct hammering

Direct hammering is in fact the process of planishing,

and the body repair worker uses it as a finishing

process after the work has been preshaped

and roughed out (Figure 13.33). It is the essential

practice to master, and develops as a result of

continuous experience.

Before using the hammer and dolly together,

it will be necessary to clean the underside of the

portion of the wing or panel on which you will

be working. Body panels and wings are covered

with a sound deadening material which must be

removed before starting the work. If you fail to

clean the surface of this material it will not only

stick to your dolly but will to a large degree

destroy its effectiveness.

Figure 13.31The technique of roughing out damage

Figure 13.32Positioning of blows in the roughing-out

technique Figure 13.33The technique of direct hammering

360Repair of Vehicle Bodies

It is most important to choose the correct dolly

block for the job, because they differ in shape,

curvature and weight. In repairing the high crowned

radius of a wing you will have to use a dolly

block with a high-crowned radius (Figure 13.34). In

repairing large body panels and door panels which

are fairly flat it is necessary to use a dolly block

with a low-crowned radius (Figure 13.35). In direct

hammering, by having a dolly which matches the

original contour under the damaged area and striking

it with a hammer, you are pushing the uneven

displaced metal surface back to its original contour

to give a smooth and level finish. The dolly provides

support and prevents the undamaged areas that have

been previously roughed out from being pushed out

of place. If you do not strike squarely over the dolly,

you will be hitting an unsupported area of the repair

and will displace the metal, creating further damage

that must be rectified later.

to push the raised points of the roughed-out section

back without flattening the surrounding metal. The

hammer should bounce back of its own accord

so that it is ready for the next stroke. Likewise the

dolly will spring away from the surface, and the

normal resilience of your arms will bring it back,

striking a blow on the metal from underneath.

These things will occur normally only if you hold

both hammer and dolly loosely.