Press brakes are an incredibly useful piece of sheet metal machinery; they are used to bend the workpiece in a variety of ways and can greatly speed up the sheet metal manufacture process. In this blog, we take a look at three different bending methods that can be achieved using a press brake.

press brake

Air Bending

The air bending method involves positioning the workpiece so that it only comes into contact with the edge of the die and the tip of the punch. The punch is driven past the top of the die into a space within the die opening, without touching the bottom. Because the punch tip does not penetrate the workpiece, the radius of the bend is controlled by the size of bottom die’s v opening, which allows the operator to alter the design by switching bottom dies. However, if dies are not selected in accordance with an air bend force chart, this method can give rise to the production of bad parts. The air bending method should be avoided when working with older, mechanical press brake models, as older machines tend to have greater margins of error.


The coining method involves stamping the sheet metal workpiece between a punch and die, so that it is permanently indented. This method uses 5 to 30 times more force than air bending, and the punch actually penetrates the workpiece. Because there is little to no spring back, the results are highly accurate and repeatable, however this method is often associated with higher costs as higher tonnages of sheet metal are needed for this method to be effective, which also results in more wear-and-tear to machinery.

Bottom Bending

Bottom bending, or bottoming, involves bottoming the workpiece against the die, allowing it to be pressed against the angle of the v opening in the bottom tool. The radius of the punch is then pushed into the workpiece, creating the angle. There is more spring back in this method than with coining, so the workpiece should be over-bended by a few degrees. The results of bottoming are highly repeatable when done properly, however the operator will need a deep understanding of tooling, tonnage, materials and timing in order to achieve satisfactory results.

All three of these methods can be achieved with a press brake, one of the most versatile pieces of sheet metal machinery. ACRA sell both new and used sheet metal machinery and stock a variety of press brake models. To determine which press brake is right for your needs, call us on 03 9794 6675.