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shear pin[′shir ‚pin]
A pin or wire provided in a fuse design to hold parts in a fixed relationship until forces are exerted on one or more of the parts which cause shearing of the pin or wire; the shearing is usually accomplished by setback or set forward (impact) forces; the shear member may be augmented during transportation by an additional safety device.
In a propellant-actuated device, a locking member which is released by shearing.
In a power train, such as a winch, any pin, as through a gear and shaft, which is designed to fail at a predetermined force in order to protect a mechanism.
A specially designed pin that shears if equipment seizes or loads beyond design values are imposed. For example, shear pins are used in arrester barriers, where they give way when an aircraft engages them beyond a given momentum. They are also used in the driveshaft of some engine-driven pumps. If the pump seizes, the shear pin breaks and allows the shaft to rotate, but the pump is prevented from further damage.