When you get a piece of flat sheet metal, it tends to be very weak, and it can be bent quite easily. So if it is so weak, why do we use this stuff for the bodies of our cars? Why not a heavier metal like metal plate? The simple answer is that, if we did , our cars would all be styled like and as heavy as a tank! This means none of those beautiful curves you see on classic cars – and I don’t want to live in that world! The truth is that sheet metal can actually be very strong once we modify and strengthen it. In this tech guide, we’re going to cover some of the ways you can modify a piece of sheet metal. Knowing techniques for how to roll sheet metal edges and create grooves in a panel are important for fabricating new body panels on a restoration project, rebuild or body repair job. These methods will give sheet metal the rigidity you need to use it in a structural or semi-structural application.
1. Sheet Metal Edge Bending
Folding over the edge of a piece of sheet metal will give the metal instant structural integrity. How large of a bend you put in the metal depends on the application and fitment of the piece. If you’re just trying to strengthen a panel, a broken edge as small as ½-inch wide can make a big difference in the strength of the panel. You can bend the metal many different ways. The simplest method is to clamp the metal down on a table and use your body weight and hands to bend it over. Another is to again clamp the metal down, but use a body hammer and the edge of a dolly to fold the metal over the dolly . This will create a bend that’s more crisp then if you just bend it by hand. The final method is to use a metal brake like the Eastwood Versa-Bend. The size and thickness of the metal you can bend in a brake is dependent on the tool itself, but most quality brakes can handle 20- and 18- gauge metals easily. Using a brake gives you a little more control and the most crisp bends possible.
2. Rolling a Hemmed/Wire Edge into Sheet Metal
This process is similar to that of breaking an edge of the sheet metal in that you’re manipulating the edge of the panel to give it rigidity. The difference here is that you put a small piece of metal wire near the edge of the panel and you fold the edge of the metal over it. Rolling sheet metal edges with wire strengthens the panel in two ways that ordinary sheet metal bending doesn’t. One is that, by metal being folded over itself it has doubled in thickness . The second is it benefits from the structural integrity that the wire hidden inside gives. This also gives a nice finished look to an edge of a panel. It was commonly done on the wheel openings of classic cars.
3. Sheet Metal with Structural Grooved Seams
Pressing grooves, ribs or designs into a piece of sheet metal will greatly increase the strength. Each groove, bead or line will compound the strength and can also add a design to the panel. The stretched metal in those areas will hold tension in the panel and give it structural rigidity. You can stretch or press beads, grooves and lines into a panel a number of ways. The most basic method is using a hammer and a chisel or punch softer than the metal itself. This could be a wooden, brass or plastic chisel or punch. You then set the metal on a surface that has a void where you’re hitting the metal. A panel beater bag is the most diverse piece of metal shaping equipment and can be used to back the panel.
The most common way to add grooved seams to sheet metal is to use a bead roller. With a bead roller, you put the metal between a male and female die that are tightened down to press the design that is cut into the dies into the metal. Bead rollers can be mechanical or electric. Finally, if you have access to big tools, you could use something like a Pullmax with matching dies to press a design in – but they take up a l ot of space and money!
4. Flared or Beaded and Punched Holes
Putting holes in a panel reduces weight, but it also reduces strength – t hat is, until you stretch or form a profile into the edge of the hole. Putting a bead or grooved seam around the hole, or flaring the hole, will give the area around said hole more strength. This process has been around for a long time, but in recent years, small d raw-t hrough p unch-f lare and p unch-b ead dies have come out. These allow you to drill a pilot hole and punch a larger hole with the desired profile around it without the need for a large press. These work much like a Greenlee knockout punch but with an extra step.
5. Stretching the P rofile of the Metal
Stretching the profile of a piece of sheet metal will greatly increase the strength of the metal. This process involves changing the shape of the metal and tends to put a bulge or curve into the panel. This can be accomplished many ways, from simply using a hammer and a sandbag, to an E nglish wheel designed for creating compound curves, to industrial methods like a power hammer. Whichever method you choose, the results are similar; it’s just how much work and time it takes to get there.
Using a combination of these methods can allow you to make a sheet metal panel strong as well as give it some nice shapes. Once you’ve gotten the hang of a few sheet metal strengthening techniques, you’ll be on your way to creating everything from fenders to trunk lids. It only requires a handful of basic metal fabrication tools, and with those, you can make most anything with enough practice and time!