Repairing Minor Body Damage - Shrinking (Drawing) Steel Sheet
1. Shrinking (Drawing) Steel Sheet
If stress and unevenness remain after the panel repair, shrink the elongated area to their original shape.
The shrinking (drawing) process is possible by heating and cooling cycles, along with use of a hammer or dolly.





Shrinking by Heating and Cooling:

If an area on the steel sheet is heated, that heated area expands. If heating is continued, elongation becomes constrained by the surrounding unheated area and further expansion becomes difficult. The surrounding area constrains and compresses the expansion. The expansion is contained to the vertical direction in the heated area. When this area is quickly cooled with water, the steel shrinks.

Do not use a torch for shrinking during actual collision repairs, because the heat is difficult to control.
Drawing by Electric Resistance:
This method makes it possible to shrink panels from the outside when full access is difficult or requires additional disassembly.
This method suitable for relatively wide and shallow damage repair.
Replace the washer welder’s electrode before use.
Press the electrode against the center of the stressed area, and turn on the switch. Shrink by moving the electrode to heat from the center of the damage outward.
Remove any warpage caused by the shrinking process by hitting lightly with a hammer and dolly.
When a carbon electrode is used, heat the stressed area in a spiral pattern moving outside toward the center as illustrated. Then air cool the area.
Remove any warpage caused by the shrinking process by hitting lightly with a hammer and dolly.
Flatten using light hammer force. If excessive force is applied, the shrunken area will be elongated again.
Using a Shrinking Hammer and Dolly:
Using a hammer or dolly that has a grid of pyramidal projections on the striking surface, hit the damaged area. When the panel is hit, tiny expansions take place, but the panel shrinks as a whole.
This method is used to repair rather small damage areas that don’t require heating.
Do not use the shrinking hammer and dolly at the same time. If a shrinking hammer or dolly is used, the counter tool must be a non-shrinking type.