5 Sheet Metal Shearing Defects and Ways to Avoid Them

Metal shearing is one of the primary processes used in sheet metal fabrication. However, defects like rough edges and deformed pieces are some of the persistent problems in using this process. Luckily, these sheet metal shearing defects are avoidable.

In this article, we dive into what these issues are, and how to resolve and circumvent them. With the right knowledge, setup, and maintenance, you can correct your process before it creates any more sheet metal shearing defects.

The shearing process is used to cut straight lines on sheet metal. First, the sheet metal is clamped into place using blank holders. Then, the material is sheared using the edges of two opposing cutting tools. One tool is a moving blade that comes down against a fixed blade, with the gap between them determined by a required offset.

To get a perfect cut you need high-quality shearing tools, able to continuously cut through various sheet metal characteristics and geometry. If not properly maintained and set up, the following defects can occur:

Burred edges are sharp, uneven pieces of metal that remain attached to a sheared metal workpiece. These can be caused by dull and blunt, or improper positioning of shear blades.

Blade position is crucial in metal shearing. In particular, the “gap” or the distance between the two cutting blades must be adjusted according to the thickness of the specimen being cut. Too big a gap and the blades will tear instead of shear, resulting in burrs. Too small a gap and the blades may not make it through the material without faltering, also resulting in burrs.

To avoid blurred edges, you can consult the shear machine’s operating manual to find the correct clearance and positioning for your material type and thickness.

Deformed edges are another defect caused by incorrect shear gaps and blunt blades. It can also be caused by faulty clamp pressures.

If the sheet metal being sheared is not clamped into place, it can wobble or become dislodged while being sheared, leading to a deformed edge. To prevent this, always double-check that the clamps are set properly, and the shearing blades are correctly adjusted and maintained.

When sheet metal pieces come off the shearing machine, sometimes there is a twist in the plate along its axis. The sheet metal may look like it is twisted into a scroll or a spin. This can be caused by cutting too narrow strips or using the wrong rake angle in the shearing blades.

The rake angle is the part that the cutting tool connects with the workpiece. If the rake angle is excessive, it makes the cut edge too thin, causing twisted sheet metal pieces. To avoid this mistake, you must adjust the rake angle according to the sheet metal’s characteristics, geometry, and cutting parameters.

Some sheet metal pieces will have edges rising slightly from the plane, creating a bowed shape. This is also caused by improper rake angles, as well as a lack of clamping and support for the sheet metal piece. Long, narrow strips of sheet metal are also more prone to bowing.

To resolve this possible defect, you should try using a smaller rake angle to best fit the sheet metal’s thickness and characteristics. Back support should also be added to better hold the sheet metal in place.

Cambering is a defect that creates varying sheet thickness along the width of the sheet metal workpiece. This happens when the sheet metal moves horizontally, but with no twisting or lifting along the edges.

The result is a convex, concave, and triangularly shaped workpiece. This can be caused by going against the grain direction of the sheet metal, and improper rake angles.

The shearing process is needed in metal fabrication to achieve clean cuts and straight-edged custom pieces. While the process can result in defects, these can be avoided provided that you follow these recommended methods:

With the right preventative measures, you can reduce the number of sheet metal shearing defects that occur in your metal fabrication project.

If you want to completely resolve this issue, we recommend partnering with trusted sheet metal fabricators, with years of shearing experience — like Regan Industrial Sales, Inc. With us, you get the work of high-quality machines and expert teams, allowing you to get your sheet metal products hassle-free. Contact us today to learn more!