Metal
The introduction of welding into the panel beaters
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 13.11 Standard wheel sets (Frost Auto
Restoration Techniques Ltd)
Figure 13.12 Split 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
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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 13.14 Planishing using a hammer and
dolly block
Figure 13.13 Planishing using a steel stake Figure 13.15 Planishing using the wheeling machine
350 Repair 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
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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 13.16 Planishing a hand-made panel
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(Autokraft Ltd)
Figure 13.17 Random 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
352 Repair 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
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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 vehicles 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 cars 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 13.18 Panel beaters hand tools (Aston Martin
Lagonda Ltd)
Figure 13.19 Fitting 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 beaters
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 companys 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 cars 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 1214 coats
of paint). This is followed by the final fit of the
vehicles 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 13.20 Panelled body shell sprayed in primer
surfacer (Aston Martin Lagonda Ltd)
Figure 13.22 Final vehicle inspection (Aston Martin
Lagonda Ltd)
Figure 13.21 Fitting 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
354 Repair 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
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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 13.23 Folded edges (a) single fold (b) folded
and creased edge (c) double folded edge
Figure 13.24 Flanged 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 13.25 Common 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
356 Repair 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 13.26 Wired edges: (a) plain wired edge and
(b), (c) creased wired edges
Figure 13.27 Wiring 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 13.28 Change in grain structure during
pressing (Sykes-Pickavant Ltd)
Figure 13.29 Prepressed wing panel
358 Repair 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 13.30 Swing 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 13.31 The technique of roughing out damage
Figure 13.32 Positioning of blows in the roughing-out
technique Figure 13.33 The technique of direct hammering
360 Repair 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.
