- Also called:
- spanner
wrench
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What is a wrench?
A wrench is a hand tool with a lever and a notched end, designed to grip and twist nuts and bolts. Wrenches come in different forms, such as open-end, box-end, and socket wrenches, each suited for specific uses. Adjustable wrenches, like monkey wrenches and Crescent wrenches, can be used for various sizes of nuts and bolts within a range. The pipe wrench is a variation used for pipes or circular bars. Power or impact wrenches use electric or pneumatic motors for quick tightening or loosening.
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What is a wrench used for?
A wrench is a hand-operated tool with a notched end that grips nuts and bolts so they can be tightened or loosened by twisting.
There are several types of wrenches:
* Open-end wrenches have straight-sided slots to fit specific bolt and nut sizes.
* Box-end wrenches fully enclose the nut, with multiple points inside the head, suitable for nuts that are hard to reach.
* Socket wrenches are short pipes with a hexagonal hole and a removable handle, used when a nut or bolt head is in a recess.
* Adjustable wrenches have one fixed and one adjustable parallel jaw for use with different sizes of bolts and nuts.
* Torque wrenches measure the amount of torque exerted on the nut or bolt.
* Pipe wrenches are used to hold or turn pipes or circular bars.
* Allen wrenches are L-shaped hexagonal bars used for screws with hexagonally shaped recesses.
* Power or impact wrenches are handheld electric or pneumatic motors that rotate socket wrenches at high speed.3 Britannica SourcesCreated from Britannica articles using AI. AI can make mistakes, so verify using Britannica articles. -
How does a wrench work to tighten or loosen bolts and nuts?
A wrench is a tool with a lever and a notched end that grips nuts and bolts, allowing them to be tightened or loosened by applying force at a right angle.
Different types of wrenches include open-end wrenches, box-end wrenches, and socket wrenches. Wrenches work by providing mechanical advantage, amplifying the force applied to the nut or bolt. Wrenches with adjustable parallel jaws can fit various sizes of nuts and bolts within a limited range.
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What are the main types of wrenches?
A wrench is a hand tool used to tighten nuts and bolts. The main types are:
- Open-end wrenches Feature straight-sided slots to fit specific bolt and nut sizes.
- Box-end wrenches Enclose the nut and have 6, 8, 12, or 16 points inside the head for turning hexagonal or square nuts.
- Socket wrenches Use a socket that fits over the nut or bolt head, with a removable handle. These often come in sets with different sized sockets and handle types like T-handles or ratchets.
- Adjustable wrenches Have one fixed and one adjustable parallel jaw for use with different sizes of nuts and bolts. The monkey wrench and Crescent wrench are included in this category.
- Pipe wrenches (or Stillson wrenches) are adjustable wrenches with serrated jaws for gripping and turning pipes or circular bars.
- Torque wrenches Measure the amount of torque applied to a nut or bolt.
- Allen wrenches Are L-shaped hexagonal bars of tool steel used for recessed-head screws or set screws with hexagonally shaped recesses.
- Power or impact wrenches Use electric or pneumatic motors to tighten nuts quickly and are often equipped with a torque-limiting device.
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How do adjustable wrenches differ from fixed wrenches?
Wrenches are tools for tightening nuts and bolts. Wrenches come in both fixed and adjustable styles to accommodate various needs.
- Fixed Wrenches These have straight-sided slots that fit specific bolt and nut sizes.
- Adjustable Wrenches These have one fixed and one adjustable jaw to fit various sizes within a range. Examples include the monkey wrench and the Crescent wrench. The first adjustable wrenches were sliding-jaw types, with the sliding jaw fixed by a wedge. Screw wrenches followed, using a screw to position the sliding jaw.
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Why is it important to use the right size and type of wrench for a specific job?
Using the correct size and type of wrench is important for specific jobs to prevent damage to both the tool and the bolt or nut. Wrenches are designed to grip and turn fasteners securely, and using the wrong size can result in slippage, which rounds off the edges of the bolt or nut, making it difficult to tighten or loosen.
Different types of wrenches, such as open-end, box-end, socket, and torque wrenches, are designed for specific applications. Torque wrenches ensure screws and bolts are tightened enough to prevent loosening without overtightening. Adjustable wrenches fit various sizes within a limited range, while pipe wrenches are for pipes or circular bars. Using the appropriate wrench ensures efficiency, precision, and safety in various mechanical tasks.
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wrench, tool, usually operated by hand, for tightening bolts and nuts. Basically, a wrench consists of a stout lever with a notch at one or both ends for gripping the bolt or nut in such a way that it can be twisted by a pull on the wrench at right angles to the axes of the lever and the bolt or nut. Some wrenches have ends with straight-sided slots that fit over the part being tightened; these tools are known as open-end wrenches and are made in various sizes to fit specific bolt and nut sizes.
Box-end wrenches have ends that enclose the nut and have 6, 8, 12, or 16 points inside the head. A wrench with 12 points is used on either a hexagonal or a square nut; the 8- and 16-point wrenches are used on square members. Because the sides of the box are thin, these wrenches are suitable for turning nuts that are hard to reach with an open-end wrench.
When a nut or a bolt head is in a recess below the surface of a bolted member, a socket wrench must be used; this is essentially a short pipe with a square or hexagonal hole and either an integral or a removable handle. Modern socket wrenches are made in sets, consisting of a number of short sockets with a square hole in one end that fits a removable handle and 8- or 12-point holes in the other end to fit various bolt and nut sizes. There are several types of handles and extensions, such as a T handle, screwdriver-grip handle, and a ratchet handle (see ratchet).
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A useful accessory for a socket-wrench set is a handle equipped with a mechanism that measures the amount of torque, or turning effort, exerted by the wrench on the nut or bolt. One type of torque handle has two arms attached to the head, which carries the socket that fits the bolt or nut to be tightened; one arm carries the torque-indicating scale and remains fixed relative to the head, while the other arm carries the handgrip and is bent, relative to the head and the scale, when a bolt is tightened. A pointer on the bent arm indicates the torque on the scale. The purpose of a torque wrench is to make sure that screws and bolts in bolted assemblies are installed with sufficient tightness to prevent loosening during use, without being overtightened.
Wrenches with one fixed and one adjustable parallel jaw can be used on various sizes of bolts and nuts within a limited range. On one type the jaws are at right angles to the handle; this wrench is known as a monkey wrench. On another type, originally called a Crescent wrench, the jaws are almost parallel to the handle. On both types the movable jaw is adjusted by turning a worm that engages a rack of teeth cut into the jaw.
The adjustable pipe, or Stillson, wrench is used to hold or turn pipes or circular bars. This wrench has serrated jaws, one of which is pivoted on the handle to create a strong gripping action on the work.
Recessed-head screws or set screws commonly have a hexagonally shaped recess and require a special wrench, usually referred to as an Allen wrench; it consists of a hexagonal bar of tool steel shaped into the form of an L, either end of which fits into the recess.
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Power or impact wrenches are used for tightening or loosening nuts quickly. They are essentially small handheld electric or pneumatic motors that can rotate socket wrenches at high speed. They are equipped with a torque-limiting device that will stop the rotation of the socket wrench when a preset torque is reached. Pneumatic wrenches are commonly used in automobile service stations, where compressed air is available and the sparking of electric motors is a fire hazard.