Repair of minor accident damage
Repairs arising from minor accidents are usually of
a relatively straightforward nature, as the damage is
either a dent, a scratch or a scruff of the outer panel
surface of the body and does not always involve
structural distortion.
When repairing it is essential to know the nature
or properties of the sheet metal used in body panels.
When a flat sheet of metal is bent to a wide radius it
will regain its former shape when released; in other
words, the metal is flexible. If this metal is bent to a
small radius it exceeds the limits of its flexibility,
and the metal in the bend becomes stiff and retains
its curved shape. These are known as rigid sections.
Therefore a body shell and panels are a combination
of rigid and flexible areas. The rigid areas are
such assemblies as door posts, sill members, roof
cantrails and flanges around wing edges and bonnets.
The flexible areas are large areas of mainly flat
or slightly curved sections such as bonnet tops,
outer door panels, sections of wings and centres of
roof panels. In the main after a collision if the
stresses are removed from the rigid areas first, then
the flexible areas (except where badly creased in the
impact) will regain their former shape. If a panel
is damaged in an accident then the buckled area,
being sharply bent, will create additional stiffness in
the panel, whether in an elastic or a non-elastic area.
The slopes 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. The theory of repair is
that areas which are elastic in manufacture, and
remain so after damage, can generally be reshaped
by their characteristics once the rigid areas in the
surrounding buckles are forced back into position.
In general the method of repair is to analyse the
crash, establish the order in which damage
occurred, and reverse the order when correcting the
damage. The majority of repairs to minor accident
damage requires the skill of the body repair worker
in the use of hand tools and general repair techniques.
Although every panel assembly has its own
individual repair procedure, the basic approach is
the same for all minor repairs and is as follows:
1 Carefully inspect the damaged area and analyse
the severity of the damage and its ease of accessibility
for repair using hand tools.
2 Decide if the repair can be carried out using
hand tools only or whether the hydraulic body
jack is required.
3 Select the necessary hand tools and, if using the
hydraulic body jack, decide which basic set-ups
and attachments are best suited to the job.
4 If the repair is carried out using hand tools only,
then the back of the damaged section under
repair, if accessible, must be cleaned of antidrum
compound.
5 If the accessibility for the use of hand tools
is difficult owing to the presence of brackets
behind the panel or double-skinned sections,
rough out the damaged area either by cutting
out the back and using spoons to lever the damage
out, or by using a panel puller on the front
of the damaged section to pull out the damage.
The area should then be cleaned, filled with the
appropriate material and finished.
6 When using hand tools only, the damaged area
should be roughed out to its original shape,
although this operation can also be carried out
using hydraulic equipment to push the damaged
section back to its original shape.
7 Once the damaged section has been reshaped,
either by hand or hydraulic means, planish it
using a combination of direct and indirect
hammering and filing.
8 Then check the low spots, if any, by cross filing
and raise them by further planishing or pick hammering.
At this stage high spots may develop due
to stretching of the metal, and hot shrinking of
these points will be necessary.
9 Sand the panel surface over the damaged area
using a very fine sanding disc.
Craft techniques and minor accident damage 383
Minor repairs to wings
Removal of a small dent from a wing is one of
the simplest of repair jobs. The first step is to check
the underside of the wing to ensure that it is free
from road dirt and anti-drum compounds; then the
damaged area is roughed out and the wing reshaped
to its original contour. The reshaping is done with a
rather heavy hand dolly of a similar shape to that of
the contour of the damaged wing section. The blows
should be heavy with a follow-through action which
will speed up the roughing-out operation. It is very
important, while roughing out damage, that fullshaped
or very curved dollies and heavy ball pein
hammers are not used, as they cause excessive
stretching of the already damaged metal. Metal that
is returned to its original pressed shape during roughing
out will smooth out more quickly and evenly.
When the roughing out is complete, the next step
is to planish the roughed area. In the case where
the wing has been heavily coated with cellulose,
it is advisable to remove this coating using the sander
fitted with an open-coated disc suitable for paint, or
with paint remover; the latter must be neutralized to
stop the burning action on the paint. The first step in
smoothing is to try to level out the uneven surface by
working the high areas into the low areas. This can
be done by holding the dolly block under the low
area and tapping down the adjacent high spot with a
planishing hammer. In some cases there may be no
high spots and no adjacent low areas, in which case
the high spots, if any, can be tapped down often with
just the planishing hammer and without the dolly
block backing. These high and low areas are found
by passing the hand over the section under repair.
As planishing continues, filing will show up any
low and high areas, which will need correcting by
tapping down high areas and lifting the low areas by
further planishing with hammer and dolly or using a
pick hammer. The final finish is achieved by cross
filing the original file strokes; this is a double check
on curvature and smoothness of the panel surface.