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A wrench or spanner is a tool used to provide a mechanical advantage in applying torque to turn bolts, nuts or other hard-to-turn items.
In American English, wrench is the standard term, while spanner refers to a specialized wrench with a series of pins or tabs around the circumference. (These pins or tabs fit into the holes or notches cut into the object to be turned.) The most common shapes are called open-end wrench and box-end wrench.
In British English, spanner is the standard term. The most common shapes are called open-ended spanner and ring spanner.
Hinged tools, such as pliers or tongs, are not generally considered wrenches.
Common wrenches / spanners
- Open-end wrench, or open-ended spanner: a one-piece wrench with a U-shaped opening that grips two opposite faces of the bolt or nut. This wrench is often double-ended, with a different-sized opening at each end. The ends are generally oriented at an angle of around 15 degrees to the longitudinal axis of the handle. This allows a greater range of movement in enclosed spaces by flipping the wrench over.
- Ring spanner, or box-end wrench: a one-piece wrench with an enclosed opening that grips the faces of the bolt or nut. The recess is generally a six-point or twelve-point opening for use with nuts or bolt heads with a hexagonal shape. The twelve-point fits onto the fastening at twice as many angles, an advantage where swing is limited. Eight-point wrenches are also made for square-shaped nuts and bolt heads. Ring spanners are often double-ended and usually with offset handles to improve access to the nut or bolt (as illustrated).
- Combination wrench, or Combination spanner: a double-ended tool with one end being like an open-end wrench or open-ended spanner, and the other end being like a box-end wrench or ring spanner. Both ends generally fit the same size of bolt.
- Flare-nut wrench, or tube wrench, or line wrench: used for gripping the nuts on the ends of tubes. It is similar to a box-end wrench but, instead of encircling the nut completely, it has a narrow opening just wide enough to allow the wrench to fit over the tube. This allows for maximum contact on plumbing nuts, which are typically softer metals and therefore more prone to damage from open-ended wrenches.
- Adjustable end wrench, or Adjustable spanner, or Shifting spanner (commonly known as a shifter or as an AJ among UK theatre techs): an open-ended wrench with adjustable (usually smooth) jaws, also sometimes called by the original patent holder's brand name as a Crescent Wrench (Crescent Tool and Horseshoe Company).
- Monkey wrench: an old type of adjustable end wrench with a straight handle and smooth jaws. These are also known in the UK as gas grips.
- Crescent wrench: the brand name of an improved version of the adjustable-end wrench (see the photo at right) developed by the Crescent Tool and Horseshoe Company. Often used as a generic term.
- Pipe wrench: an adjustable-end wrench with self-tightening properties and hard serrated jaws that securely grip soft iron pipe and pipe fittings. Sometimes known by the original patent holder's brand name as a Stillson Wrench.
- Socket wrench: a hollow cylinder that fits over one end of a nut or bolt head. It may include a handle, but is usually used with various drive tools. It generally has either a six-point or twelve-point recess, may be shallow or deep, and may have a built-in universal joint. The drive handles generally used are:
- Break-over (or hinged) handle: This handle is also known as a jointed nut spinner or flex head nut spinner, and often as a breaker bar in the United States. It is a long non-ratcheting bar. Breaker bars are often used to free stuck bolts and nuts. The additional length of a breaker bar allows the same amount of applied force to generate significantly more torque than a standard length ratchet wrench.
- Ratchet handle (contains a one-way mechanism which allows the socket to be turned without removing it from the nut or bolt simply by cycling the handle backwards and forwards).
- Speed handle (sometimes called a crank handle or speed brace).
- Screwdriver handle (for use of the socket as a nutdriver).
- Sockets are often sold as a set containing a collection of sockets of various sizes and associated drive tools; usually including, as a minimum, extensions, a ratchet driver, and a universal joint. Sockets are also used with various power tools.
- Crowfoot socket wrench: a type of socket designed to fit some of the same drive handles as the regular socket but non-cylindrical in shape. The ends are the same as those found on the open-end, box-end, or the flare-nut wrenches. These sockets use for use where space restrictions preclude the use of a regular socket. Their principal use is with torque wrenches.
- Saltus wrench: similar in concept to a socket wrench. A Saltus wrench features a socket permanently affixed to a handle. Sockets are not interchangeable as with a socket wrench. The socket often rotates around the handle to allow the user to access a fastener from a variety of angles. Commonly a Saltus wrench is part of a double-ended wrench, with an open-end type head on the opposite side from the socket head.
- A mole wrench, also known as a mole grip, is not a wrench but a type of self-locking pliers.
- A box spanner (UK) is a tube with 6-sided sockets on both ends. It is turned with a short length of rod (tommy bar or T bar) inserted through two holes in the middle of the tube.
- Slogging/flogging Spanner: A spanner (both open and ring types are available) with a block end to the handle specifically designed for use with a hammer. Typically used to release large nuts and bolts where the shock of the impact is useful in breaking rust or paint.
Other general wrenches / spanners
- Wrenches for screws and bolts with internal sockets are generally referred to in the UK as keys, and include:
- Hex key, Allen wrench or Allen key: a (usually) L-shaped wrench fabricated from hexagonal wire stock of various sizes, used to turn screw or bolt heads designed with a hexagonal recess to receive the wrench.
- Bristol wrench, or Bristol spline wrench: another wrench designed for internal socket-head screws and bolts. The cross-section resembles a square-toothed gear. Not a common design, it is chiefly used on small set screws.
- TORX wrench: an internal socket-head screw design. The cross-section resembles a star. Commonly used in automobiles, automated equipment, and computer components as it is resistant to wrench cam-out and so suitable for use in the types of powered tools used in production-line assembly.
- Strap wrench or chain wrench: a self-tightening wrench with either a chain or strap of metal, leather, or rubber attached to a handle, used to grip and turn smooth cylindrical objects. In bicycle repair circles it is known as a chain whip and is used to remove and install cassettes on rear hubs.
- Alligator wrench: a formerly common type of wrench that was popular with mechanics, factory workers, and farmers for maintenance, repair and operations tasks in the days when fasteners often had square rather than hex heads. The wrench's shape suggests the open mouth of an alligator.
- Breaker bar: A breaker bar is an extended-length handle for socket wrenches that adds extra torque for loosening strongly tightened or frozen fasteners.
Specialized wrenches / spanners
- Spoke wrench or spoke key: a wrench with a clearance slot for a wire wheel spoke such as a bicycle wheel and a drive head for the adjustment nipple nut.
- Peanut butter wrench or crank (bolt) spanner: a wrench used by cyclists to tighten cranks (wheel nuts), and to scoop out peanut butter from a jar.
- Tap wrench: a double-handled wrench for turning the square drive on taps used in threading operations (cutting the female threads such as within a nut) or a precision reamer.
- Die wrench: A double-handled wrench for turning the dies used in threading operations (cutting the male threads such as on a bolt).
- Torque wrench: a socket wrench drive tool that measures the amount of rotational force applied to the socket—this may be indicated visually with a rod or dial or may simply slip when a set torque is exceeded. The torque wrench would also be categorized as a measuring tool.
- Drum wrench: a tool commonly used to open bungs on large 55 gallon drums.
- Lug wrench: a socket wrench used to turn lug nuts on automobile wheels. Commonly known in the UK as a wheel brace.
- Plumber wrench: a tool to screw (rotate with force) various pipes during plumbing.
- Tuning wrench: a socket wrench used to tune some stringed musical instruments.
- Oil-filter wrench: a type of wrench for removing cylindrical oil filters. It may be either a strap-type wrench or a socket.
- Sink wrench: a self-tightening wrench mounted at the end of a torque tube with a transverse handle at the opposite end. Used to tighten tubing connections to washstand valves in ceramic sinks—the nuts are often located deep in recesses. The self-tightening head may be flipped over to loosen connections. Also known as a Basin wrench.
- Podging Wrench or Podger: A steel erecting tool which consists of a normal wrench at one end and a spike at the other, used for lining up bolt holes. In the U.S. often called a spud wrench.
- Golf shoe spike wrench: a T-handle wrench with two pins and clearance for the spike—allows removal and insertion of spikes in shoes.
- Head nut wrench: a flat wrench with a circular hole and two inward protruding pins to engage slots in the nut. This type of nut is used on bicycles to secure the front fork pivot bearing to the headpiece of the frame.
- Fire hydrant wrench (hose connection): The hose connection has a threaded collar with a protruding pin. From the handle of the wrench an arc has at its end a loop to engage the pin.
- Fire hydrant wrench (valve operator): This is a pentagonal (five-sided) box wrench. Avoiding a hex shape for the lug makes the valve tamper-resistant: with the opposite faces nonparallel, unauthorized opening of the hydrant is less likely, because the would-be opener lacks a suitable tool.
- Chain wrench: Similar to a pipe wrench, but uses a chain similar to a drive chain, instead of an adjustable jaw. The links of the chain have extended pegs which fit into grooves in the front of the handle, with one end of the chain attached permently to the handle. This is used in situations where pipe wrenches can't maintain a proper grip on an object such as a wet or oily pipe. Larger versions of chain wrenches are sometimes known as "bull tongs" and are used with large diameter pipe such as is used deep wells.
- Left-handed wrench: A non-existent tool which is often the object of a fool's errand.
- Air impact wrench: A compressed air (pneumatic) powered wrench commonly used in car garages and workshops to tighten and remove wheel nuts.
- Graduated wrench: An adjustable wrench with a small number (usually 2-4) of discrete sizes. This is sometimes used as an inexpensive substitute for a monkey wrench.