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 strengthen a sheet metal panel by modifying it. Knowing techniques for how to roll sheet metal edges and create grooves in a panel is important for fabricating new body panels on a restoration project, rebuild or body repair job. These sheet metal strengthening methods will give sheet metal the rigidity you need to use it in a structural or semi-structural application while keeping your vehicle lightweight.
- 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 in many different ways. The simplest method is to clamp the metal down on a table, then 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 crisper than 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 are 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 crispest bends possible.
(Photo Courtesy of MetalMeet.com
2. Rolling a Hemmed/Wire Edge into Sheet Metal
This process is similar to that of edge bending in that you’re manipulating the edge of the panel to give it rigidity. The difference is that with sheet metal edge rolling, 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 that it benefits from the added structural integrity of the wire hidden inside. This also gives the edge of a panel a nice, finished look. The metal rolling technique 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. Some of the most common sheet metal bends and seams include:
- Straight bends
- Flanges
- Z-shaped bends (aka Offsets)
- Hems (either a U- or C-shaped bend)
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 lot of space and money!
One thing you will need to be careful of when bending or pressing sheet metal is causing cracks in the outside of the metal. This can occur since more strain is placed on the outer metal than the inner metal. To prevent cracks, the minimum “bend radius” — the imaginary circle you’re bending the metal around — should be at least equal to the thickness of the sheet.
4. Flared or Beaded and Punched Holes
Putting holes in a panel reduces weight, but it also reduces strength — that 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 draw-through punch-flare and punch-bead 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.
If you want a different visual look or don’t have the width needed for holes, you also can punch and flare slots in the metal to achieve similar results. For either shape, you should place the holes/slots at least 1/16-inch from the nearest wall or edge on sheet metal that’s 20 gauge or thinner, and 1/8-inch from the edge on all other metals. Additional clearance may be needed if you plan to add an insert or fastener.
5. Stretching the Profile 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 in many ways, from simply using a hammer and a sandbag, to an English 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 almost anything with enough practice and time!
For more sheet metal strengthening tips and tricks, visit the Eastwood Garage and How-To Center or call our tech experts at 1-800-343-9353. Eastwood also has a growing network of brick-and-mortar stores where you can speak to a real person and check out many of the tools we mentioned in this guide. We’ve been helping DIY auto body workers Do the Job Right since 1978.
Usually, I try to use structural grooved seams and wire edges to make my sheet metal stronger, but I would like to know more about what I can do to make it stronger than by simply using the methods that I already know. I liked your last tip to stretch the profile of my metal. I’ll try stretching it by using a hammer and a sandbag to an English wheel and see how that works out. Thanks for the tips!
The beads can be created whenever you’d like as long as you can fit it through the machine. Sometimes the beads must be done first before shaping the part and other times it is done as the last step.
The structural grooves you referred to is an excellent way to provide extra strength to sheet metal. By adding the extra surface area and indents, the metal is better supported with near beam-like structures. Do you know if these grooves can be added after fabrication or if they can only be created while the metal is fresh? I’ve only seen them pre-made, but would be interested in making them myself.
Very helpful information. Fixing to do my floorpans from scratch and needed this.
A kit just like that will be out late summer/early fall. Thanks for reading!
Excellent information. You should make a kit of hole punch and flare from 1” to 2.5” in 1/2” increments that would be great.
Great article very informative and practical As a metal worker and inventor for the last 35 years its a pleasure to see a commercial business such as yours take ownership and pride in passing the skills on I teach my three sons and all of there friends at every oppertunity we have. Despite being blessed with an excellent high school with great teachers they often dont have the class time. Your approach was excellent and I commend you for demonstrating the hand forming methods as well. It would have been easy and understandable if you made it as a machine demo.I hope you can continue these they would add to Eastwood strong reputation perhaps you could put them together as a DVD. Great work Jeff Pitman Southpaw Garage 95 years mechanics\welding\fabricating
Hi Barry,
Those punch flare and punch bead dies are in stock in the first size currently with the other sizes coming later this summer. See them here: http://search.eastwood.com/search?w=dimple+dies&ts=custom
Hi Mark, we just released the first size of those with the other sizes following late this summer. Find them here: http://search.eastwood.com/search?w=dimple+dies&ts=custom
Keep up the good information. Has to promote sales.
This article is sorely needed by those of us that have mechanical skills, but have no training since high school metal shops no longer exist in quantity and quality that I experienced in the 1960’s. There are sources for the equipment used herein-yourself as well as auctions. The restoration industry and self esteem of the car builder stands to benefit incalculably!
I saw the dimple dies that were used to make the bomber bench on project Pilehouse. I was told that they could be available through Eastwood sometime this year. Is there still a chance they will become available?
Very Good , instruction segment , on the punch .is east wood going to be having them in the inventory , in the future ? Thanks
great help
Very informative and spoke on a level easily understood
keep these coming
Very good basic information. Ironically I found this post at exactly the right time. I will have to make partial rear window frames for my new project a 64 cutlass holiday coupe. Of course I will purchase the items necessary to complete this project from Eastwood. Thank you, Jim
I hope this is an ongoing service Eastwood is providing , I’ve been buying tools all my life and have some things I don’t know how to use in the correct way. I will follow anything service you provide and try to master it. Thank you and Eastwood.
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Louie B
The information in this article was very good it is nice to hear some of the other options to metal forming other than the tools that most of us can not aford to buy.
Very interesting, enjoyed it very much. Thanks
Great knowledge