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Adjustable spanner
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An adjustable spanner, shifting spanner, shifter, 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 many European countries (e.g.
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Encyclopedia
An adjustable spanner, shifting spanner, shifter, 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 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 counries, 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) 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.
More recently, in the 1990s, a further improvement was made by another Englishman, Ian Harrison, who invented a precision adjustable spanner, something that previously had been thought to be a contradiction in terms! The gnurled 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 its patented ratchet mechanism. In two movements - pulling back on a release button and pushing up the leg of the bottom jaw - the spanner is locked on and cannot slip. Known as a "milli-grip" because it is currently available in metric models, the ratchet moves in increments of 1mm. This same patented ratchet mechanism can be adapted to produce imperial models, moving in increments of 1/16th of an inch.
Monkey wrenches are another type of adjustable wrench with a long history; the origin of the name is unclear.
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. This reduces the risk of deformation of the movable jaw or the adjusting mechanism, thus avoiding the increase of backlash.
This type of wrench should never be used on a rounded off nut, as this can overload the movable jaw. Nor should the wrench be used "end on" in cramped quarters, 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. In some parts of Europe they are often called a Bahco, which is a genericized trademark as well.
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