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A vise or vice (see American and British English spelling differences) is a mechanical screw apparatus used for holding or clamping a work piece to allow work to be performed on it with tools such as saws, planes, drills, mills, screwdrivers, sandpaper, etc. Vises usually have one fixed jaw and another, parallel, jaw which is moved towards or away from the fixed jaw by the screw.
Without qualification, "vise" usually refers to a bench vise with flat, parallel jaws, attached to a workbench. There are two main types: a woodworking vise and engineer's vise. The woodworker's bench vise main characteristic is its integration into the bench. An engineer's bench vise is usually clamped or bolted onto the top of the bench. The handle is usually adjustable so that it can be tightened in small places. 
Woodworking vises 
For woodworking, the jaws are made of wood, plastic or from metal, in the latter case they are usually faced with wood to avoid marring the work piece. The top edges of the jaws are typically brought flush with the bench top by the extension of the wooden face above the top of the iron moveable jaw. This jaw may include a dog hole to hold a bench dog. In modern metal woodworkers' vises, a split nut is often used. The nut in which the screw turns is in two parts so that, by means of a lever, it can be removed from the screw and the moveable jaw can be quickly slid into a suitable position at which point the nut is again closed onto the screw so that the vise may be closed firmly onto the work.
Engineer's vises 
An engineer's vise, also known as a metalworking bench vise or fitter's vise, is used in metalworking applications. They are made of cast steel or malleable cast iron for strength. Cheaper vises may be made of cast iron, being somewhat brittle and at risk of breakage when applying too much force or if struck with a hammer. The jaws are separate pieces made of soft or hard metal, usually with serrated or diamond teeth engraved into them. Extra-soft jaws are often used to protect the workpiece, usually as additional jaw covers clipped over the main jaws. These are made of aluminum, lead, plastic or red fibre. The vise is bolted onto the top surface of the bench with the face of the fixed jaws just forward of the front edge of the bench. The bench height should be such that the top of the vise jaws is at or just below the elbow height of the user when standing upright. The vise may include other features such as a small anvil on the back of its body.
The nut in which the screw turns may be split so that, by means of a lever, it can be removed from the screw and the screw and moveable jaw quickly slid into a suitable position at which point the nut is again closed onto the screw. The disadvantage to this system is lower precision, as compared to a solid screw system. Vise screws are usually either of an Acme thread form or a buttress thread. Those with a quick-release nut use a buttress thread. Some vises have a hydraulic or pneumatic screw, making setup not only faster, but more accurate as human error is reduced.
For large parts, an array of regular machine vises may be set up to hold a part that is too long for one vise to hold. The vises' fixed jaws are aligned by means of a dial indicator so that there is a common reference plane.
For multiple parts, several options exist, and all machine vise manufacturers have lines of vises available for high production work:
- The first step is a two clamp vise, where the fixed jaw is in the center of the vise and movable jaws ride on the same screw to the outside.
- The next step up is the modular vise. Modular vises can be arranged and bolted together in a grid, with no space between them. This allows the greatest density of vises on a given work surface. This style vise also comes in a two clamp variety.
- Tower vises are vertical vises used in horizontal machining centers. They have one vise per side, and come in single or dual clamping station varieties. A dual clamping tower vise, for example, will hold eight relatively large parts without the need for a tool change.
- Tombstone fixtures follow the same theory as a tower vise. Tombstones allow four surfaces of vises to be worked on one rotary table pallet. A tombstone is a large, accurate, hardened block of metal that is bolted to the CNC pallet. The surface of the tombstone has holes to accommodate modular vises across all four faces on a pallet that can rotate to expose those faces to the machine spindle.
- New work holding fixtures are becoming available for five-axis machining centers. These specialty vises allow the machine to work on surfaces that would normally be obscured when mounted in a traditional or tombstone vise setup.
There are two main types of jaws on engineer's vises: hard and soft. Hard jaws are available with either a coarse gripping surface or are ground flat and smooth to increase accuracy. The latter relies on pressure for gripping, instead of a rough surface. An unskilled operator has the tendency to overtighten jaws, leading to part deformation and error in the finished workpiece.
Soft jaws are usually made from a soft metal (usually aluminum), plastic, or wood. They are used to either hold delicate workpieces or cut to hold specifically shaped workpieces. These specifically cut jaws are often used in place of fixtures and most commonly used in gang operations. They are also used for rapid change-over type set-ups since they can be easily engraved with the part number, the job number, or other information relevant to the job being run. Soft jaws are considered a consumable item, because they are discarded or recycled after multiple uses.
Other kinds of vise include:
- hand vises
- machine vises - drill vises (lie flat on a drill press bed). Vises of the same general form are used also on milling machines and grinding machines.
- compound slide vises are more complex machine vises. They allow speed and precision in the placement of the work.
- cross vises, which can be adjusted using leadscrews in the X and Y axes; these are useful if many holes need to be drilled in the same workpiece using a drill press. Compare router table.
- off-center vises
- angle vises
- sine vises, which use gauge blocks to set up a highly accurate angle
- rotary vises
- diemakers' vises
- pin vises (for holding thin, long cylindrical objects by one end)
- jewellers' vises and by contrast
- leg vises, which are attached to a bench but also supported from the ground so as to be stable under the very heavy use imposed by a blacksmith's work.
See also 
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