Three Kinds of Shear

Shear stress is force acting parallel to a surface, divided by the area resisting it. It shows up three common ways. Direct shear is a pin, bolt or rivet cut across its shank — stress is simply force over the cross-section, halved if the pin is in double shear. Punching shear is a punch driving through a plate, where the resisting area is the hole perimeter times the thickness. Beam shear is the transverse shear inside a loaded beam, which peaks at the neutral axis rather than spreading evenly.

Does It Pass? Strength and Safety Factor

A stress number on its own does not tell you much. What matters is how it compares to what the material can take. The shear strength of a ductile metal is roughly 58% of its tensile yield (the von Mises result) or about 60% of tensile ultimate. Divide that by a safety factor to get the allowable working stress; if the applied shear stays under it, the part passes. This calculator reports the actual safety factor so you can see how much margin is left.

Single vs Double Shear

A pin in double shear is cut across two planes instead of one, so each plane carries half the load and the stress halves. That is why clevis joints are so common — the same pin and the same material suddenly has twice the capacity. Adding a shear plane is often the cheapest way to make a failing joint pass.