Panel patching steps
The following steps describe how to remove chrome plastic fender vents and replace with a solid steel patch to create a more unique, sharper profile on a truck. This is a popular exterior modification. The directions here can serve as a model for performing other similar fabrication services.
Step 1. Pry off the vent using a plastic trim tool to reveal the recessed area underneath.
Step 2. Create a template for the replacement metal. Cut a rectangular piece of poster board slightly larger than what will be needed. Use masking tape to attached it to the fender fully covering the vent area. Using a marker and your finger, press on the edges of the recessed area and draw several plus signs, one in line with the edge and one perpendicular to the edge, to create an outline of the vent. Do this along the entire outer edge of the vent area. Use a ruler to connect all the intersecting points. Complete using a ruler and an exacto knife to cut out the template.
Step 3. Test the template by fitting into the vent area. It should sit as flush as possible to reduce the amount of filler and additional body work later.
Step 4. Carefully trace the shape onto a piece of 18-gauge steel.
Step 5. Cut out the shape with a plasma cutter using two pieces of 1/4 in. bar as a guide to make the cuts straight.
Step 6. Attach a 60 grit flap disc to a 4.5 in. grinder and remove the burrs and any surface rust. Bevel the edges to ensure the patch sits flush with the panel, which will help provide a much cleaner weld.
Step 7. Curve the patch piece to match the slight curve of the factory with a bench top English wheel. Carefully apply only forward and backward pressure on the patch in line with the wheel. Placing too much side pressure on the patch will create a dome that will not match the contour of the fender. You can also avoid creating a dome by placing a rubber band over the upper wheel. Doing so reduces the side-to-side stretching of the metal since the band stretches in its place.
Step 8. Test the panel patch. Use a magnet to hold the patch piece in place. Examine the fit and gaps from multiple angles to make sure no corners are too high or out of place. If necessary, grind any unsatisfactory areas into shape. Spray the back of the patch with a self etching weld thru primer to prevent rusting from the inside.
Step 9. Prep the panel area. Place a flap disc on a 4.5 angle grinder. Remove the paint down to the bare metal all the way around the areas that will be welded.
Step 10. Fit the patch into the panel in the proper position. Using a TIG welder, tack weld the panel into place.
Step 11. Examine the weld. If the patch is no longer sitting flush, you can adjust it without having to cut the piece out to save the welds. Using a wide flat blade screw driver, put half of the blade on the patch and half on the panel. Press the patch so it sits just below flush with the opening; then place a tack weld right above the blade. If the panel sits too low in the opening, use a very fine flat blade screwdriver to pry the panel up to the desired depth.