Minor repairs to door panels
When repairing door panels the main difficulties
arise through the fact that most door panels are
nearly flat sheets of metal, which means that even
the slightest stretching due to over-hammering will
produce a fullness which will stand out after the
repair has been painted. The greatest care must be
taken.
The first step is to strip the door of interior trim
and window. The amount of stripping necessary
depends on the extent and position of the damage.
With most door repairs it is quicker to remove the
door from the vehicle by releasing the check strap
and then taking out the set screws in the door
side of the hinges, or, if the hinge is welded, by
knocking the hinge pin out. Having prepared the
door and the work bench, an inspection can then
be made of the door frame to determine the accessibility
for the use of hand tools and hydraulic
equipment. When carrying out the repairs it is
often necessary to cut the back of the door frame
and bend it, thus permitting greater freedom of
movement for the use of hand tools. The thorough
removal of all anti-drum material is essential
before any actual planishing is commenced.
The shape is gained by roughing out with the
mallet and dolly block, after which the finish is
attained with the planishing or pick hammer in
conjunction with the file. In selecting a dolly it is
advisable to choose one that is rather light and
slightly flatter than the panel being planished. This
will reduce the risk of stretching the panel. In some
cases where the door panel is badly creased and is
inaccessible for the use of hand tools, it would be
better to rough out the damage with the aid of the
body jack or spoon acting as a lever, smooth it over
with hammer and dolly, then fill it with body
solder and file the area to obtain the final finish.
Reskinning door panels
This process affords considerable saving in time
and cost compared with the practice of replacing
complete door assemblies. The technique of this
process is the same regardless of the shape or type
of door to be reskinned:
Removal of a damaged skin panel This is
achieved by drilling out the spot welds around
the flanged areas of the door using either a Zipcut
or cobalt drill or Spotle tool and also, on some
types of door, using a power saw to make joints
across the pillars (Figure 13.63a). The flange can
be then eased up using a flange removing tool
(Figure 13.63b), or in some cases the outer edges
of the flange are ground through using a sander
(Figure 13.63c). If this method is used, care must
384Repair of Vehicle Bodies
(a)
(d)
(f)
(b)
(c)
(e)
Craft techniques and minor accident damage 385
be taken not to damage the door frame. The
damaged panel skin can then be removed using
a hammer and chisel and easing up the flange
strips that are left (Figure 13.63d).
Preparing door flanges The door flanges should
now be straightened up using a hammer and dolly
and the face of the flanges sanded to make a smooth
surface for the attachment of the new skin panel.
Preparing the new surfaces The door flanges
should now be painted with a zinc-rich interweld
primer to stop any chance of corrosion
between the door flange and the new skin
(Figure 13.63e).
Fitting the new skin panel The prepainted skin
panel is now placed over the frame and aligned
using the door lock holes as a guide, and MIG
tacked on to the joint pillars if necessary. The
edges of the skin are now hammered over the door
frame using a hammer and dolly until the flange
is folded over completely. During this operation
great care is essential if the panel face is not to be
marked (Figure 13.63f).
Welding in the new skin panel The spot welds
should now be replaced to fix the new skin panel
to the frame, taking care to use the correct electrodes,
especially on the face side of the panel.
Adhesive is used on certain doors to fix the skin
panel to the door frame. Where joints have been
made in the pillars they must be MIG welded,
ground flush and soldered (Figure 13.63g).
(g) (h)
(i)
Figure 13.63Reskinning door panel: (a) removing
spot welds (b) removing flanges (c) grinding
through flanged edges (d) removing damaged skin
panel (e) priming door frame (f) folding door edge
flanges (g) soldering the pillar joints (h) finishing
panel edges (i) completed reskinned door
(Motor Insurance Research Repair Centre)
386Repair of Vehicle Bodies
Final cleaning and inspection The soldered
joints must be filed and sanded with a DA sander.
Finally, inspect the skin panel for any defects,
which will need correcting by filing and sanding
(Figures 13.63h and 13.63i).
Pulling out double-skin
Panel damage
When inaccessible body panels are damaged, a
method of repair for the removal of the damage,
without leaving holes or having to remove interior
trim, is to use a special pin welding gun. Also
pin welding attachments can be fastened to spot
welding equipment (Figure 13.64). The welding
gun attaches pins, screws, washers or studs to the
surface of any damage so it may be pulled out.
There are two sizes of pins: small (2 mm) which
are normally used for skin panel damage, and
larger (2.5 mm) which are used for chassis legs
or thicker-gauge metals.
First the damaged area must have its paint
removed and be sanded down to a bare metal finish
in order to give a good electrical contact
between the pin and the welding gun. Insert the
pin into the spring-loaded nozzle of the gun. The
two points of contact are the tip of the pin and
the outer copper ring on the welding gun, which
should, when pushed down, make as even a
contact as possible with the panel surface under
repair. Press the gun to the surface of the metal,
press the trigger for 1–2 seconds only and remove
the gun from the pin, which now should be
welded to the panel. The number of pins which
need to be welded on to the panel will vary in
accordance with the depth and extent of the damage,
starting at the deepest section of the damage
and working outward.
The dint is then gradually pulled out using a
slide hammer, which tightens on to both sides of
the pin by the rotating action of the chuck. The
dinted area is then pulled out by using the slide
hammer action, on one pin at a time, beginning at
the deepest part of the damage and working outwards.
The pins are removed by breaking them
from the panel surface and sanding down their
residue.
When the damage is a crease and very deep,
ring washers may be used instead of pins to facilitate
a stronger pull. A clamp may be fastened
to these washers and attached by chain to pulling
equipment which would then pull out the damage.
Alternatively a hook is inserted into the slide
hammer to pull out each washer individually
(Figures 13.65 and 13.66).
When the damage has been completely pulled out
the area may be filled using body solder or plastic
filler according to the position and extent of the damage.
The filled area is then sanded and filed down to
an acceptable finish for painting.
Minor repairs to bonnets
The bonnet of a car is firmly fastened when closed.
Many models have spring loaded hinges so that the
tension of the springs holds the bonnet firmly in
place at the hinge side. At the point of locking a
sturdy catch holds the bonnet down under spring
tension. When open the bonnet is virtually unsupported
as it is only held in place by the hinges.
This means that only minor repairs can be carried
out with the bonnet in place, and if hydraulic
power tools are necessary it is advisable to remove
the bonnet from the car. Large areas of almost flat
sections running into gradual return sweeps are
incorporated in the designs of most bonnets. The
flat panel and the return sweep are both shapes that
need careful repairing to avoid stretching of the
metal.
A rather common trouble that arises when
repairing bonnets is the development of a loose
edge. This looseness usually occurs along the back
edge of the bonnet, which in most cases is a raw
edge, and even the slightest stretch will cause a
buckle. It is essential that this buckle be removed,
and the best way of carrying this out is by hot
shrinking the edge. Another characteristic of bonnets
is that the edge flanges crack, and these
should be welded as early as possible to prevent
the extension of the crack and to keep the bonnet
in its correct shape.
The repair procedure for minor, accessible dents
is first to rough out the damaged area using a mallet
to minimize stretching, and then to planish the
area using a beating file in conjunction with a dolly
block which will also reduce the possibility of
stretching. If the repair is in such a position as to
make the use of hand tools difficult because of the
strengthening struts, the area should be roughed
out using very thin body spoons and then filled
Craft techniques and minor accident damage 387
with plastic filler, as the heat produced when
soldering might distort the panel. The prominent
position of the bonnet requires its finish to be
perfect because ripples and low spots can be easily
seen when painted.