Shear Stress

Shear stress is the internal mechanical stress distribution that develops within material as the upper and lower shear blades compress and separate it, ultimately causing the material to fail in shear and separate cleanly into two pieces. The shear strength of a material (measured in pounds per square inch) combined with the cross-sectional area of the cut determines the total force required to complete the cut, which must not exceed the machine's hydraulic or mechanical capacity.

For example, cutting 1/4-inch mild steel across a 4-foot width requires significantly more force than cutting 1/16-inch aluminum of the same width because the cross-sectional area is much larger. Understanding shear stress helps fabricators predict whether a material can be cut on available equipment, and it also explains why blade rake angle and blade clearance optimization can reduce the force needed for difficult materials. Exceeding a machine's shear stress capacity results in incomplete cuts, machine strain, and potential equipment damage.