Manufacturing: Metal Forming

Sheetmetal Forming - Shearing

Shearing is a metal fabricating process used to cut straight lines on flat metal stock. During the shearing process, an upper blade and a lower blade are forced past each other with the space between them determined by a required offset. Normally, one of the blades remains stationary.

Characteristics of the shearing process include:

• Its ability to make straight-line cuts on flat sheet stock
• Metal placement between an upper and lower shear blades
• Its trademark production of burred and slightly deformed metal edges
• Its ability to cut relatively small lengths of material at any time since the shearing blades can be mounted at an angle to reduce the necessary shearing force required.

Limitations -

The use of shears in sheet metal production has diminished through the use of cut-off tooling in CNC punching and the use of shake-out technology to separate parts from the sheet skeleton. Shears are used mainly for rough shearing sub-sizes of sheets for CNC presses or strips for stamping press dies.

In those cases where finished dimensions are sheared, the thickness of the material and the X-Y dimension of the part dictate the degree of precision which is feasible economically. Thicker material and greater X-Y dimensions require greater tolerances.

Process -

Typically, the upper shear blade is mounted at an angle to the lower blade that is normally mounted horizontally. The shearing process performs only fundamental straight-line cutting but any geometrical shape with a straight line cut can usually be produced on a shear.

Metal shearing can be performed on sheet, strip, bar, plate, and even angle stock. Bar and angle materials can only be cut to length. However, many shapes can be produced by shearing sheet and plate.

Materials that are commonly sheared include:

1. Aluminum
2. Brass
3. Bronze
4. Mild steel
5. Stainless steel