Sheet metal duct work, drain pans and other products that contain large, flat sections of metal will often generate noise or disfigure under pressure. Stiffening the sheet metal reduces noise and increases the strength of a metal component. The nature of sheet metal allows stiffening without adding additional material and weight to the finished piece. The process of stiffening sheet metal--known as cross braking--places a small bend across flat sections of metal. Each bend reduces the flat area of each side, increasing its overall strength.
Increase the gap between the top and bottom dies of sheet metal brake by either pushing the clamping leaf handle away from the front of the brake or pressing the "Raise" button of a press brake.
Slide a piece of sheet metal into the opening between the top and bottom dies of the brake.
Align two diagonal corners of the sheet metal with the point of the top brake die. Lower the top brake die to clamp the piece of sheet metal in place.
Continue lowering the top die of the press brake until the sheet metal extending beyond the brake raises 5 degrees above the point of the die, or pull the lower bending handle of a leaf brake until the metal sits 5 degrees above the lowest point of the top die. Raise the brake's top die.
Spin the sheet metal until the two remaining corners align with the point of the brake's top die. Use the described method to perform a second bend across the sheet metal. Remove the sheet metal from the brake. The finished piece will have an "X" crossing the centre of the sheet metal.
Keep hands and fingers clear of the moving parts of a sheet metal brake to avoid serious injury.