An adjustable spanner or adjustable wrench is an open-end wrench with a movable jaw, allowing it to be used with different sizes of fastener head rather than just one fastener size, as with a conventional fixed spanner. Several other names are in use, including casually imprecise use of the US trademark crescent wrench.
Forms and names
English engineer Richard Clyburn is credited with inventing an adjustable spanner in 1842. Another English engineer, Edwin Beard Budding, is also credited with the invention. Improvements followed: on 22 September 1885 Enoch Harris received US patent 326868 for his spanner that permitted both the jaw width and the angle of the handles to be adjusted and locked. Swedish company Bahco attributes an improved design, in 1891 or 1892, to Swedish inventor Johan Petter Johansson who in 1892 received a patent. In Canada and the United States, the tool is known as a Crescent wrench or an adjustable wrench. In Australia it is referred to as a "shifting spanner", usually abbreviated to "shifter". 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. 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. The tool is therefore usually angled so that the movable jaw's area of contact is closer to the body of the tool, which means less bending stress. Still, one should avoid applying excessive force on tight bolts, since doing so can pry open the mounting of the movable jaw causing the wrench to no longer be able to be snugged to bolt heads, loosen too easily, or mar bolt heads. In some cases the jaws of the tool can break. Monkey wrenches are another type of adjustable spanner with a long history; the origin of the name is unclear. A popular type of adjustable spanner has a base and jaws that form four sides of a hexagon, and is therefore particularly suited for hexagonal nuts and hexagonal headed cap screws and bolts. In the United States and Canada, the adjustable spanner is sometimes colloquially referred to as a "crescent wrench" due to the widespread Crescent brand of adjustable wrenches; the former Crescent Tool Company was the assignee of the 1915 U.S. patent for the most familiar form factor of adjustable wrench. The Crescent brand of hand tools is now owned and marketed by Apex Tool Group, LLC. In some parts of Europe, adjustable spanners are often called a Bahco. This term refers to the company of the Swedish inventor Johan Petter Johansson, which was originally called B.A. Hjort & Company. The Swedes themselves call the key "skiftnyckel", which is translated into adjustable key. In Australia, adjustable spanners are also referred to as "shifters".
