Allen key is also known as a/an ___________.

Question

Prepp Team · Accepted Answer

Understanding Allen Keys and Their Names

The question asks for another name for an Allen key. An Allen key, also known as an Allen wrench or hex key, is a simple tool used to drive bolts and screws with hexagonal sockets in their heads. These types of screws are often used as set screws because the head doesn't protrude.

Why "Hollow Set Screw Wrench"?

Allen keys are specifically designed to fit into the hexagonal hole, or "hollow" part, found in the head of certain screws and bolts, particularly set screws. A set screw is typically used to secure a pulley, gear, or other component onto a shaft. Many set screws have this hexagonal socket drive. Because the Allen key is frequently used with these screws and works by engaging the "hollow" (socket) in the "set screw", the term "hollow set screw wrench" became a common alternative name.

Analysing the Options

Let's look at the given options and see why some are correct and others are not:

Hollow set screw wrench: As explained above, this is a widely accepted alternative name for an Allen key, directly relating its use with set screws that have hexagonal sockets (hollow centres).
Open end wrench: An open end wrench has a U-shaped opening at one or both ends and is used for gripping the external sides of nuts and bolts. It is completely different from an Allen key.
Pipe wrench: A pipe wrench is a heavy-duty tool with adjustable jaws designed for gripping and turning pipes or fittings. Its function and design are very different from an Allen key.
Adjustable wrench: An adjustable wrench (also known as a crescent wrench) has one fixed jaw and one movable jaw, allowing it to grip nuts and bolts of various sizes. Like the open end wrench, it grips external surfaces and differs significantly from an Allen key.

Based on the design and common usage of an Allen key, the name "hollow set screw wrench" accurately describes its primary function and application with set screws.

Comparison of Wrench Types
Tool Name	Description	Primary Use
Allen Key (Hex Key)	L-shaped or T-shaped rod with hexagonal cross-section. Fits into hexagonal sockets.	Driving screws/bolts with hexagonal sockets (often set screws).
Open End Wrench	U-shaped opening at ends. Grips external sides of fasteners.	Turning nuts and bolts.
Pipe Wrench	Heavy-duty tool with adjustable jaws. Grips cylindrical objects like pipes.	Turning pipes and fittings.
Adjustable Wrench	Adjustable jaw to fit various fastener sizes. Grips external sides.	Turning nuts and bolts of varying sizes.

Conclusion

Comparing the options, the term "hollow set screw wrench" is the only one that correctly serves as an alternative name for an Allen key due to its common use with set screws featuring hexagonal sockets.

Revision Table: Hand Tools and Wrenches

Common Hand Tools
Tool Category	Examples	Key Feature
Wrenches/Spanners	Allen key, Open End, Socket, Adjustable, Pipe	Used for turning fasteners (nuts, bolts, screws) or pipes.
Screwdrivers	Phillips, Flathead, Torx	Used for driving screws with different head types.
Pliers	Needle-nose, Slip-joint, Locking	Used for gripping, bending, cutting wires or small objects.

Additional Information: History and Sizes

The Allen key system was developed by the Allen Manufacturing Company in the early 20th century, hence the name "Allen key". The use of hexagonal sockets provides several advantages over traditional screw heads like slotted or Phillips:

It allows for higher torque application.
It is less likely to strip the head.
The screw head can be smaller relative to the thread size.
The socket design allows the screw head to be flush or below the surface, useful for set screws.

Allen keys come in various standard sizes, specified in either metric (in millimeters, e.g., 4 mm, 5 mm) or imperial (in inches, e.g., 1/8 inch, 5/32 inch). It is crucial to use the correct size Allen key for the screw socket to prevent damage to both the tool and the fastener.