Locking pliers

''This article is about the tool. For the Vise-Grip company, see Vise-Grip (manufacturer)''.

Locking pliers, also known by the trade name Vise-Grip, are pliers which, when applied to the work piece, can lock in place. Once locked, the grip of the tool stays in place, making the locking pliers similar to a third hand. Traditional designs require the user to reset the gripping tension when the tool is applied to differently-sized work pieces, though a new design by C. H. Hanson allows Set-and-Forget™ tensioning. Many or all designs use a mechanical linkage to allow multiply the force applied by the user beyond the simple multiplying factor of handle length.

Once locked, the grip of a pair of locking pliers is independent of the user's squeezing power, enabling the locking pliers to provide strong, uniform grip, similar to a wrench. Most designs of locking pliers can be tightened with a thumb screw after they have been applied, and later designs include a socket for a hex-key in the thumb screw, enabling the user to further tighten the screw. A new design by C.H. Hanson features a redesigned locking mechanism that allows the user to set the gripping strength independently of the jaw size, theoretically allowing the user to set the tension once and never set it again. In practice, a user needing to adjust the tension will need to release the tool to do so, since the adjustment screw of this design in hidden once the pliers are locked in place.

Locking pliers of either design are useful as welding clamps, makeshift handles, for removing stuck nails, and many other uses where normal pliers are inadequate.

The mechanism of the locking pliers has also been applied to clamps.