(f). Flatten the edge with hammer or sizing block, and remove the burr with file to make sure that it is aligned
with the both side alternative plates with a clearance not more than 1mm;
(g). Replace the plate, and clamp it with pincers. Carry out the spot welding along the seam at a space of
approximately 50mm;
(h). Make the welding from the center to both sides alternately block by block. Which can reduce the
deformation;
(i). Strike the welding line with the hammer or sizing block to remove the retaining stress. Polish the welding
lien wit the file or manual grinding wheel to make it even and smooth for the painting.
c. Repair for Accidented Damage
(a). Plate work flattening
When the accidented damage occurs on the plate work of the body, it can be repaired by means of beating.
In the repair process, start from Point C as shown in Fig. 5-26. Put the sizing block on the convex point, and beat
it with the hammer and change the block's position correspondingly. When the convex point is flattened, the
concaved part in Point B will rise. Similar wit the original profile of the plate, for the remaining dent, a sizing block
with the same radian can be employed. Press the bottom of the plate with hand, and beat the high point of the dent
with the hammer. (Fig. 5-27)Fig. 5-27 Plate Work Flattening (II)
A. Hammer B. Plate work
C. Sizing block Fig. 5-26 Plate Work Flattening (I)
A. Impact point B. Concaved point after impact
C. Convex point after impactFig. 5-28 Heating & Planishing
Convex Point
1. Heating pointBody Repair -Repair After Body Damage7-19 In the beating process, beat the work piece heavily at the beginning and lightly at the end. Attention shall
be paid to reduce the number of beating as possible as it can. Don't beat the same points repeatedly to prevent the
metal plate extending locally, which can complicate the repair work.
For the larger arc concave, a sizing block can be used under the center of the concave. The area of the sizing
block shall be a little larger. Jack the concaved plate up with a supporting tool. Sometime, heat the concaved part
to wine color to reduce the force. When jacking the plate up, a little excess is acceptable. (Fig. 5-28)
(b) Thermal contraction
When the concave is jacked up, if the plate extends seriously and the area is large, the thermal contraction
method can be used in case that the traditional methods don't work. (Fig. 5-29)
Heat the work piece to cerise color with oxyacetylene flame. The heating scope depends on the degree of extension.
If the extension is serious or the area is large, the heating point shall be larger relatively (diameter: approx.20-
30mm). If the extension is not serious or the area is small, the heating point shall be a little smaller (diameter:
approx.10-15mm). After the heating, beat the heating point immediately. In the beating process, a proper sizing
block is used under the plate. After it is cooled down, beat it lightly with the hammer.
The contraction starts from the highest point to the center, and then to the edge. Heat and flatten the extended
part repeatedly till the plate is flattened fully. If the convex part is too high, compress it to one half of the original
height. After it is cooled down, heat it at the original heating point till the other half of convex part is removed.
Fig. 5-29 Thermal Contraction Method For those parts that are not sure whether they will contract or not, the thermal contraction method shall not
be used to avoiding any side effect. Especially for those thin plates, great attention shall be made to prevent them
from melting down or burning through.
(c) Welding ring
The welding ring method is used to repair the most seriously damaged part of the concave on the plate work
surface. Some rings are welded to connect the rods. (Shown as Fig. 11-30) When the area of the concave is large,
several rings can be welded in a parallel manner, and gets through the rod to make the pulling force act on the plate
surface evenly. The ring can be replaced by the washer. The rod pulls the washer or shaft through a coupling device.
After the concaved plate is flattened by the inertia hammer puller, remove the ring or washer and finish the welding
points.Fig. 5-30 Welding Washer StretchingBody Repair -Repair After Body Damage7-20Washer WasherHeating
Compress
loadCooling
Extend load Plate work
thermal contraction Metal bar thermal
contractionWasherShaft
Shaft Shaft Rod
