Complex Rust Patch Panel Made Easy

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.

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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.

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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.

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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.

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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.

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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.

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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.

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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.

-Matt/EW

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43 thoughts on Complex Rust Patch Panel Made Easy

  • Hi , I am so pleased i saw this demonstration on this type of repair. The tub on my F 100 has rusted in the same place ,every time i walk past it i stop and look at it to see if i can think of an idea to fix it . Where do you get those bending wheels from? Great idea.
    Thanks for the Tips , Graeme

  • This Tech Tip couldn’t have come at a better time. I have a same issue on the interior rear floor just below the rear truck door on my English Ford. A 1955 Ford Popular. This will work out great on the repair.

    Thank you, Matt

  • Matt,I’ve seen your video of the pilot house chop, way cool! I’m restoring a ’39 Plymouth pick up that’s pretty solid for 75 years old. I bought a donor cab for the roof, mine met a large tree. Braced both cabs and measured and checked for 2 days before cutting. All went well.I’m now replacing back,bottom of cab like you. I made my patch panel angle from the seat bracket from the donor cab. Recycing at its best. Thanks for sharing the nice work you do

  • this was very interesting I’m in the process of some rust work on a 1963 1/2 Ford Galaxie 500 fastback. not much rust but in all the wrong places.

  • Hi Tom,

    Sounds like a fun project! Those old Plymouth pickups are a rare breed! Feel free to share your progress with us as you go. Thanks for following along!

  • Hi Graeme,

    We offer those forming wheels for the bead roller on our website. They should fit all manual bead rollers with the 7/8″ mandrel like ours.

  • I have seen this method before and it can work if you have a form to hammer against, but you do have to take care not to overstretch the metal with the air chisel. I’d suggest practicing on a smaller piece of metal first.

  • Always nice to see practical applications and approaches. If anyone want to see a master metal former at work check out Lazze on Youtube. He has an excellent site that offers free videos on bead rollers, shrinker stretcher, English wheel. I have learned so much.

  • Great write up and information. I might add you can also complete this type a fabrication with out a tipping/ bead roller, I have completed many. Make your pattern out of card stock, for the horizontal metal, transfer to metal as indicated in the article. At the rear edge, I have either rolled with a radius die or formed with hammer and radius edge dolly. Place the panel aside and repeat the same procedure for the vertical panel, including the radius edge. Now mate the two pieces together and weld it either with TIG or MIG. Use proper welding methods to limit distortion. Metal prep the panel and install with clecos, magnets, or other clamps for the final welding to the existing metal.

    I have a few pictures of a complex patch that I completed on my sons Honda behind the front fender, wheel house , unfortunately, I do not know how to load photos here.
    As with all metal work, I have found there are different methods to achieve the same results. Practice… and more practice.

  • I’m working on a 42 MB Jeep and this was great information, I’d would have loved to see it on a video.

  • Great point Jeff! More than one way to do a job and come out with the same results. Thanks for the great input!

  • What can be done when welding a small repair patch when ya can’t get to the back side of the weld to clean and prime ,paint? welding starts the rust process

  • Good article. Hammer and dollying mig welds is tough the welds tend to be brittle and will break. Tig welds you can beat on all you like

  • I love the info. good pictures very informative. Can always use info from other peoples projects. mines a 54 chevy truck . putting it on 74 blazer frame thank you

  • The best bet is to use an access hole in the backside or drilling a small hole and applying our Internal Frame Coating.

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