A vise screw is the part of a vise that draws the two jaws together and separates them. Depending on the design of the vise, the vise screw may be positioned towards the middle of one of the jaws or along one of the edges of the vise. The length of the screw determines how wide the jaws can open.
A simple vise has two jaws and a vise screw. In most cases, one jaw of the vise is stationary and is sometimes built onto the side of a workbench or other sturdy structure. The other side of the vise is movable and is attached to the vise screw. When turned, the vise screw allows this jaw to move towards or away from the other jaw so that the tool can grasp tightly onto a piece of wood, metal, or other material that a person is working with. When the vise screw is properly tightened, the jaws of a vise will hold an object steady without denting, cracking or otherwise damaging it.
Many old-fashioned vises that are made from wood have a wooden vise screw. Though these screws are not as strong as their metal counterparts, they can be used when working with woods or other soft materials. Metal vise screws, which can be used with either wooden or metal vises, make for a stronger vise that can grasp an object more tightly.
The end of the screw used to tighten the vise is often outfitted with a handle or crank. This makes it easy for a person to turn the screw to open or close the vise. Alternatively, many modern vises use a ratchet or even a hydraulics system. Ratchets are often attached to vise screws that open and close the vise quickly while hydraulics are used on heavy-duty or industrial vises.
The design of a vise screw is similar to other types of screws. The body of the screw is threaded so that it remains in place once the vise is closed around an object. Vise screws with threading that is close together take more revolutions to move the jaws but can allow for more precise positioning while vise screws with threading that is wider apart allows the screw to move the jaws more quickly. The length of the screw, along with the length of the arm holding the movable jaw, controls how far the vise can open and close.