vise

Three types of vises

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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.

Varieties of vises

Without qualification, "vise" usually refers to a bench vise with flat, parallel jaws, attached to a workbench.

• A woodworker's bench vise is a more or less integral part of the bench.
• An engineer's bench vise is bolted onto the top of the bench.

Engineer's bench vise or fitter's vise - image inset shows soft jaws

Machine vise - mill

Small machine vise - drill

Woodworker's vise

Other kinds of vise include:

• hand vises (hand-held),
• 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 solving triangles and gauge blocks to set up a highly accurate angle,
• rotary vises,
• diemakers' vises,
• table 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.

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.

Metalworkers' vises

For metalworking, the jaws are made of metal which may be hardened steel with a coarse gripping finish. Quick change removable soft jaws are being used more frequently to accommodate fast change-over on set-ups. They are also kept for use where appropriate, to protect the work from damage.

Metalworking bench vises, known as engineers' or fitters' vises, are 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. Where several people use the one vise, this is a good guide.

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. Many fitters prefer to use the greater precision available from a plain screw vise. The vise may include other features such as a small anvil on the back of its body.

Vise screws are usually either of an Acme thread form or a buttress thread. Those with a quick-release nut use a buttress thread.

Metalworking vises in machine shops

In high production machine work, work must be held in the same location with great accuracy, so CNC machines may perform operations on an array of vises. To assist this, there are several machine-shop specific vises and vise accessories.

Hard and soft machine jaws have a very important difference between other metalworking vise jaws. The jaws are precision ground to a very flat and smooth surface for accuracy. These rely on mechanical pressure for gripping, instead of a rough surface. An unskilled operator has the tendency to over-tighten jaws, leading to part deformation and error in the finished workpiece. The jaws themselves come in a variety of hard and soft jaw profiles, for various work needs. One can purchase machinable soft jaws, and mill the profile of the part into them to speed part set-up and eliminate measurement. This is most commonly done in gang operations, discussed below. For rectangular parts being worked at 45 degree angles, prismatic hard jaws exist with V grooves cut into them to hold the part. 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 the CNC machine.

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.

See also

• Parallels

External links

Look up vise in Wiktionary, the free dictionary.

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