Overlap/Backing Plate Sectioning - Welding
Warning : Refer to Approved Equipment for Collision Repair Warning in the Preface section.
- Fit the service panel to the vehicle to ensure a proper fit.
- Measure and mark a line at the sail panel 120 mm (4 3/4 in) from the back glass opening and 70 mm (2 3/4 in) rearward from the sill panel locating hole edge of the service panel.
- Cut along the line to trim the service panel.
- Fabricate a 50 mm (2 in) backer plate so that the panel will fit behind the sectioning joint at the sail panel.
- Fabricate a 100 mm (4 in) backer plate for the rocker panel.
- Drill 8 mm (5/16 in) plug weld holes as necessary in the locations noted from the original panel.
- Bevel the sail panel and service panel edges at the sectioned area to approximately 10 degrees.
- Grind a 50 mm (2 in) area of the outer surface on the vehicle to remove any corrosion, E-coat, primers, coatings and galvanizing that may be present.
- At the section area on the service panel, grind a 50 mm (2 in) area of the back side to remove any corrosion, E-coat, primers, coatings and galvanizing that may be present.
- Drill plug weld holes approximately 13 mm (1/2 in) from the edge of the cuts the sectioning areas of the service panel and the original panel.
- Prepare all mating surfaces as necessary.
- Apply GM-approved weld-thru coating or equivalent to all mating surfaces. Refer to
Anti-Corrosion Treatment and Repair : Base .
- Position and clamp or screw the backer plate with half of the backer plate exposed at the sectioning joint.
Note : Leave a gap of 1 1/2 times the thickness of the metal at the sectioning joint to the original panel.
- Position the service panel to overlap the backer plate and 1 1/2 times the thickness up to the original panel.
- Check for proper fit and alignment to the vehicle. Clamp the panels together.
- Plug weld the backer plate accordingly.
- Stitch weld along the entire sectioning joint, make 25 mm (1 in) welds along the seam with 25 mm (1 in) gaps between them.
- Complete the stitch weld.
- Clean and prepare all welded surfaces of the entire sectioning joint.
Note : Always follow the system manufacturer's instructions for application, handling, and curing.
- Apply a lightweight body filler to the backer plate area.
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