Press brakes are the perfect tool to finish any machine shop collection. A close cousin to inventor George Keene’s cornice brake (which he patented in 1887), today’s press brakes use a hydraulic or electric servo-powered ram together with a set of male and female dies to form or bend sheet metal into some pretty amazing shapes.
DIY Sheet Metal Bending
There’s just one problem. Like most metal processing equipment, press brakes are expensive, and unless you have one in your garage, you’ll need to pay a metal fabricator to bend your parts. Here at SendCutSend, that’s a pretty simple process, especially if we’re already cutting your parts for you. But sometimes, a design can be altered so you can bend sheet metal parts yourself and it’s almost as simple as having us bend them for you.
With a little ingenuity and some clever CAD work, a laser can cut bend lines in practically any sheet metal part, making it as easy to fold as a paper airplane. (Maybe not, but we can dream right?) I know, I know, you don’t have a laser cutter either, but we do—seven of them, actually—and we’re happy to share a little known method of leaping over the press brake hurdle and getting your project back on track.
Sheet Metal Bending At Home
So how does it work? We promise it’s not magic, though it feels pretty damn close. Here are some step-by-step instructions to help you visualize this process:
- Grab an old book off your bookshelf and tear off the back cover (make sure it’s not from the public library, or the one that your Mom gave you for your birthday last year that you have yet to read.)
- Using a fine marker, carefully draw a series of shapes on your pretend piece of sheet metal to look like Figure 1 below.
- Now, take an X-Acto knife and cut those shapes out. Be careful not to hurt yourself. Feel free to make humming noises while pretending to be a laser cutter. It makes you go faster. Trust us, we’re experts.
- When you’re done cutting along those lines, pick up your masterpiece and bend it along the line. See how easy it was, and how cleanly it folded? Problem solved, no press brake needed.
Bridging the gap
Granted, this little exercise wasn’t done with metal, although it could have been. We routinely make these “wave cuts” in aluminum, steel, titanium, brass, and more, allowing our customers to bend their parts by hand and avoid an extra step in the fabrication process. That said, there are some guidelines you should know about before starting:
- The Gap: in our book cover example, the width of the white line is 0.075” (1.905mm). The cuts you design should be 0.5 times that of the material thickness and a bit more than that in heavier or harder metals. For example, 0.125″ aluminum would need a gap of 0.075″ (1.905mm), while 0.187″ mild or stainless steel should be 0.130″ (3.302mm) or so.
- The Tab: the little angled section between each slot is called the tab. Measured as the crow flies, it should be at least the width of the material thickness across. Make it too wide and you’ll need arms like Arnold Schwarzenegger to bend the part; too narrow, and the part will be weak.
- The Length: Similarly, it’s up to you to determine how long each slot should be and therefore how many of them are needed across the bend length. Again, it depends on the type of material, its thickness, and the width of the bend, but a half dozen or so would be a good starting place for a typical part.
- The Tail: If you have a two-foot long part with a fold in the middle, each “tail” will measure one-foot in length. Thanks to the huge amount of mechanical leverage in our example, it’s as easy as bending cardboard. Make that part just 6-inches long, however, and you’ll have better luck trying to bend your coffee table in half. To fix that, just add more tabs by shortening the slot length.
It’s easy, we promise
Confused? It’s actually easier than it sounds. If you’re a CAD person,, we have some .dxf templates you can use. You should also be aware of something that press brake operators know intimately: when you bend metal, you lose a little bit of material to the radiused section (something called OSSB, or outside setback). You’ll need to add that amount to your part length to achieve the correct dimensions. The formula for OSSB is relatively simple:
OSSB = [Tangent (degree of bend angle/2)] × (Material thickness + Inside radius)
Our sheet metal bending calculator is also helpful for knowing how your parts will look after they’re bent and what you need to do to prepare your design for bending. We’re here to help if you run into trouble. Happy bending!