Pronunciation: [hˈɛks kˈiː] (IPA) 
Hex key, also known as Allen key, is a type of tool with a hexagonal cross-section used to tighten or loosen bolts and screws with hexagonal sockets. The spelling of the word "hex key" is phonetically transcribed as /hɛks ki/, with the first syllable pronounced as "heks" and the second as "key." The word "hex" refers to the six-sided shape of the tool, while "key" signifies its function as a tool for operating a mechanism or a lock.
A hex key, also known as an Allen wrench or Allen key, is a type of tool used to tighten or loosen screws and bolts with hexagonal sockets or heads. It is commonly used in various industrial, automotive, and household applications.
Hex keys are typically L-shaped or have a T-handle design, featuring a long, slender body with a hexagonal cross-section at one or both ends. The hexagonal shape corresponds to the shape of the socket in the screw or bolt head. The tool is inserted into the socket and rotated to either tighten or loosen the fastener.
Hex keys are available in a wide range of sizes, usually indicated by the width across the flats (the distance between two opposite faces) of the hexagonal cross-section. This sizing system ensures that the hex key fits the corresponding fastener tightly without slipping during operation.
The primary advantage of using a hex key is its ability to deliver high torque with minimal slipping or stripping of the fastener head. This makes it efficient for tasks that require significant force, such as assembling furniture, installing machinery, or repairing bicycles.
In summary, a hex key is a versatile hand tool designed for engaging with hexagonal fasteners. Its design and range of sizes allow for precise and secure tightening or loosening of screws and bolts, making it a valuable tool in various mechanical and DIY applications.
The word "hex key" originated from a combination of two distinct origins:
1. "Hex" comes from the Greek word "hexa" meaning "six". It refers to the six-sided shape of the most commonly used type of hex key, known as the hexagon or hexagonal socket.
2. "Key" in this context refers to a tool used to turn or operate a mechanism. It is derived from the Old English word "cǣg" or "cǣge", which meant a key or a toothed instrument. Over time, the term "key" came to represent various types of tools used to turn or fasten things.
Therefore, the term "hex key" combines the specific shape of the tool (hex) with its function as a turning instrument (key).
