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.

Наши рекомендации