An adjustable spanner or adjustable wrench is a spanner with a "jaw" of adjustable width, allowing it to be used with different sizes of fastener head (nut, bolt, etc.) rather than just one faster, as with a conventional fixed spanner. An adjustable spanner may also be called a shifting spanner, shifter, fit-all, or adjustable angle-head wrench.
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In many European countries (eg France, Germany, Portugal, Spain and Italy) the adjustable spanner is called an "English key" as it was first invented in 1842 by the English engineer Richard Clyburn. Another English engineer, Edwin Beard Budding, is also credited with the invention. Improvements followed: on 22 September 1885 Enoch Harris received US patent 326868[1] for his spanner that permitted both the jaw width and the angle of the handles to be adjusted and locked. Other countries, like Denmark, Poland and Israel, refer to it as a "Swedish key" as its invention has been attributed to the Swedish inventor Johan Petter Johansson, who in 1891 received a patent for an improved design of the adjustable spanner that is still used today. Johansson's spanner was a further development of Clyburn's original "screw spanner". In some countries (e.g. Egypt, Hungary, Iran, Slovenia, Poland, Romania) it is called "French key" (in Poland, "Swedish" or "French" key depending on type). In the USA, a spanner is universally called a wrench.
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. Some adjustable spanners automatically adjust to the size of the nut. Simpler models use a serrated edge to lock the movable jaw to size, while more sophisticated versions are digital types that use sheets or feelers to set the size.
Monkey wrenches are another type of adjustable spanner with a long history; the origin of the name is unclear.[2]
The movable jaw should be snugly adjusted to the nut or bolt head in order to prevent damage to the fastener's head, or rounding. In addition, it is important when applying significant force to ensure that the fixed jaw "leads" the rotation (it follows its tip) and the movable jaw "trails" the rotation, leaving its tip behind, so to speak. The area of contact for the fixed jaw should be farther from the body of the tool. That means the movable jaw's area of contact is relatively close to the body of the tool, which means less bending stress. The fixed jaw can withstand bending stress far better than can the movable jaw, because the latter is supported only by the flat surfaces on either side of the guide slot, not the full thickness of the tool.
This type of spanner should not be used on a rounded off nut, as this can overload the movable jaw. Nor should such a spanner be used "end on" in cramped quarters (except perhaps when the nut is barely more than finger-tight), where a ratchet is more appropriate.
In the United States, the most well-known brand of adjustable spanner (adjustable wrench) is the Crescent® wrench. This brand is so well known in the USA that the term is often used generically–the trademark is becoming diluted. This brand of hand tools is owned and marketed by Apex Tool Group, LLC. In some parts of Europe, adjustable spanners are often called a Bahco.[3] The reason for calling it refers to the company of the Swedish inventor Johan Petter Johansson, which was originally called B.A. (Bernt August) Hjort & Company.