At times rust repair can be ultra simple; cut the old rust out, cut a square of fresh metal and weld it in. But those repairs aren’t usually as frequent as we’d like. Rust seems to like to creep into a curved area or into a body line that takes more care to repair. I recently decided to tackle a large rusty area of the rear portion of the floor on Project Pile House. This area was behind the seat and sat under the original gas tank. Over the years a rusty tank leaked and contaminated the metal underneath. What I was left with was swiss cheese. I wanted to replace this metal completely and make the repair relatively stock looking.
A big part of making a rust repair job go smoothly is to study the damaged area and really think through the repair process before just cutting right into the car and having to change direction afterwards. Above you can see what I was working with. The center section of the panel was rotted away completely and the surrounding areas were eaten away. I also had rust that had rusted away on the back lower outer cab sheet metal, what a mess! I decided to remove the entire width of the floor section that was damaged so I could repair the lower cab skin more easily. I started by using a pneumatic body saw to cut along the corners and the front edge of the damaged area; leaving the stepped bead in place. The majority of the back panel was separated from the metal, so I got off easy. Originally the back panel would have been spot welded to the flange on the floor and they would have had to been drilled out. Cutting the panel this way will leave a clean butt weld between the original floor and the new patch panel.
With the damaged area out we can really see what we’re working with. The metal is very bad in the center as we imagined, but I also noticed it was rotted evenly along almost the entire flange that would have been spot welded to the back of the cab. Another complication was because the part fits in the curve of the back of the cab; the flange and the stepped bead changed dimensions across the piece. I decided to take measurements off of the best side of the part and transfer them to a piece of cardboard to get the initial shape of the patch panel.
With overall shape of the panel laid out on the cardboard. I took a scribe and traced the outside shape of my pattern. I then used a set of dividers and transferred the width of the back flange into the new metal. The scribed line will eventually be my line where we turn the flange. I then removed the pattern and used a divider again to mark out the stepped bead line.
Finally I cut out the patch with the electric shears, leaving an 1/8th or less of the line and came back with the aviation snips to cut accurately right on my cut line. I then used a fresh sharpie to mark my bend and bead line.
Next I mounted the manual bead roller in the vice and set up the offset step dies to make the stepped bead in the panel for strength. I ran a few test pieces to get the size and depth of the bead pretty close to the original. With a helper I rolled the step into the panel.
I then switched the dies and inserted the soft lower wheel and the smallest radius upper die on the bead roller. This step you won’t be able to do in one pass no matter how fancy or expensive of a bead roller you have. You first must make a pass with moderate pressure between the dies and pull up lightly on the panel as it rolls through the rollers. This first pass creates a “track” for the wheel to run in and subsequent passes require less effort to keep the dies on the line. This means more focus can be put on the upward pressure used to tip the flange. Above you can see the panel after three passes. Depending on the shape of your panel it may fight you in the corners because it is trying to tip and there’s too much metal to move. This was the case in our situation. You can solve this by tuck shrinking the corners or putting relief cuts in the corners, removing the excess overlapped metal and welding the seams. The shape of our piece I couldn’t quite get a 90 degree flange on in the bead roller so I used a hammer and dolly to fold the edge over the last few degrees.
With the panel shaped I test fit it in the truck and it should fit well with some very minor adjustments. Before welding the panel in place I’ll clean the entire panel with fast etch. Other than making the pattern, the most tedious part was hammering the flange over the last few degrees. Hopefully anyone with a similar repair can get some ideas from how I did this one.