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Adjustable spanner

Adjustable wrench
Adjustable spanner

An adjustable spanner, shifting spanner, shifter, fit-all, crescent wrench or adjustable-angle head wrench (American English) is a tool which can be used to loosen or tighten a nut or bolt. It has a "jaw" (the part into which the nut or bolt goes) which is of adjustable size, which allows for different size nuts and bolts to be handled by the same spanner. Compare this to the ordinary spanner which has a fixed size.

In Europe so-called French key
In Europe so-called English key

In many European countries (e.g. France, Germany, Spain and Italy) it is called an "English key" as it was invented in 1842 by the English engineer, Richard Clyburn. Other countries, like Denmark, refer to it as a "Swedish key" as its invention has been attributed to the Swede, Johan Petter Johansson, who in 1891 received patent for an improved design of the adjustable spanner. Johansson's spanner was a further development on Clyburn's original "screw spanner". And in some contries (e.g. Slovenia, Poland) it is called "French key".

There are many forms of adjustable spanners, from the taper locking spanners which needed a hammer to set the movable jaw to the size of the nut, to the modern screw adjusted spanner.

There is a class of adjustable that automatically adjust to the size of the nut. The most modern are digital types that use sheets or feelers to set the size, and other simpler models that use a serrated edge to lock the movable jaw to size.

In the 1990s, a further improvement was made by another Englishman, Ian Harrison, who invented a precision adjustable spanner. The knurled wheel design of the traditional adjustable spanner has always meant that it could take some time to adjust it to different sized nuts or bolts and also, once placed on the nut or bolt, could easily slip off, either rounding the edges of the nut or damaging the user's hand. Harrison's invention avoids both these problems with a ratchet mechanism.[1]

Monkey wrenches are another type of adjustable wrench with a long history; the origin of the name is unclear.[2]


Proper use

The movable jaw should be snugly adjusted to the nut or bolt head in order to prevent rounding.

In addition, it's important to ensure that the movable jaw is located on the side towards which the rotation is to be performed, so that the jaw that is of the same piece as the handle receives the majority of the force when torque is applied via the tool to the fitting or fastener. This reduces risk of deformation of the movable jaw or the adjusting mechanism. Using the tool on the wrong side, in a manner such that the non-moveable jaw does not receive the greater part of the manually applied force, increases backlash against the moveable parts. That may result in damage to the tool or in slippage-related damage to the fitting or fastener.

This type of wrench should not be used on a rounded off nut, as this can overload the movable jaw. Nor should such a wrench be used "end on" in cramped quarters (except perhaps when the nut is barely more than finger-tight), where a socket wrench is more appropriate.

Genericized trademark

In the United States, the term crescent wrench is often used by the general public as a generic term to indicate any adjustable spanner. In actuality, the Crescent brand of hand tools is owned and marketed by the Cooper Tools division of Cooper Industries.[3] In some parts of Europe they are often called a Bahco, which is a genericized trademark as well.[1]


  • Monkey wrench
  • Pipe wrench or Stillson wrench
  • Plumber wrench


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