A wrench or spanner is a tool used 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.) In British English, spanner is the standard term.
Wrenches are generally one of two types: the double–handled wrench (see image at right) and the end wrench; with the end wrench, by far, the most common. Hinged tools, such as pliers or tongs, are not generally considered wrenches.
- 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.
- Box-end wrench, or Box spanner, or Ring spanner: a one-piece wrench with a enclosed opening that grips the faces of the bolt or nut. The recess is generally a six-point or twelve-point opening. The six-point is used for nuts or bolt heads with a hexagonal shape. The twelve-point can be used with either square or hex shaped nuts and bolt heads but is not as durable. Box-ends are also often double-ended.
- 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 wrench or ring spanner. Both ends generally fit the same size bolt.
- Flare-nut wrench, or Tube wrench: used for gripping the nuts on the ends of tubes. The design is similar to a box–end wrench but with an opening to allow the wrench to fit over the tube.
- Adjustable end wrench, or Adjustable spanner, or Shifting spanner: 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: the original adjustable end wrench with a straight handle and smooth jaws.
- 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, incorrectly, 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—may include a handle but 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. In additon face driving sockets are available. These are more durable still, and have the ability to drive a range of hexagonal head sizes, with less risk of damaging the nut or bolt head than traditional "corner" drivers. The drive handles generally used are:
- a break–over (or hinged) handle.
- a ratchet handle (contains a mechanism which allows the socket to be turned without removing it from the nut or bolt).
- a speed handle (sometimes called a crank handle).
- a 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 principle use is with torque wrenches.
Other general wrenches
- Wrenches for Screws and Bolts with internal sockets.
- Hex key wrench or Allen Wrench: 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 this wrench.
- Bristol® wrench: another wrench designed for internal socket head screws and bolts. The cross-section resembles a square-toothed gear. Not a common design.
- Torx® wrench: a relatively recent internal socket head screw design. The cross-section resembles a star. Fairly commonly installed with automated equipment.
- Strap or Chain wrench: a self-tightening metal or leather strap or a chain attached to a handle, used to grip and turn smooth cylindrical objects.
- Spoke wrench: a T-handle wrench with a clearance slot for a wire wheel spoke such as a bicycle wheel and a drive head for the adjustment nut.
- 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.
- 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.
- 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.
- Wrench Description & Use, 8 pages; from Integrated Publishing; Commercial site but no pup-ups. (http://www.tpub.com/content/aviation/14001/css/14001_14.htm)