
A hex key, also commonly referred to as an Allen key, Allen wrench, Alum key or hex wrench, is an essential tool for driving bolts and screws with hexagonal sockets. Its simple, compact design—typically L-shaped or T-shaped—provides effective torque control, making it a staple tool in both professional and household applications worldwide.

The hex key’s unique 6-sided tip fits securely into hexagonal socket screws, allowing for the application of significant torque without slippage. This straightforward design reduces wear on fasteners and minimises the risk of rounding, contributing to the hex key’s popularity in a variety of applications, from furniture assembly to precision mechanical work.

These tool are widely used because they are lightweight, easy to store, and affordable. Their compatibility with a vast range of hex socket screws and bolts also them a go-to tool across industries. The precise fit also enhances safety, reducing the risk of tool slippage or damage to the fastener.

## **Types of Hex Key**

Hex keys come in several types, each with specific advantages for different applications.

- **L-Shaped Hex Keys:** The most common type, L-shaped hex keys offer versatility with a hexagonal tip on each end. This design allows users to alternate between the short and long arm for leverage or to access tight spaces.
- **T-Shaped Hex Keys:** T-shaped hex keys, or T-bar Allen keys, have a crossbar or T-handle, providing a better grip and improved torque. They are particularly useful in applications requiring consistent, high-torque fastening.
- **Folding Allen Key Sets:** Similar to a multi-tool, folding hex key sets feature multiple sizes housed within a compact, foldable casing. This design is ideal for portability and convenience, allowing users to carry multiple sizes in a pocket or tool kit.

### **Other Types**

Expanding on other hex key variations, including:

- **Ball-End Hex Keys:** Ball-end hex keys offer the advantage of a rounded tip, enabling use at an angle—typically up to 30 degrees. This flexibility is useful in tight or awkward spaces, such as when fastening screws at difficult angles.
- **Long-Arm and Short-Arm Hex Keys:** Long-arm hex keys provide increased leverage, allowing for greater torque, while short-arm keys are compact and ideal for reaching into tight spots. The choice between long and short arms depends on the specific needs of the task.

## **Surface Coatings of Hex Keys**

Surface coatings on hex keys enhance durability and prevent corrosion, which is important for tools exposed to high moisture or harsh environments. Common hex key coating and their benefits include:

- **Black Oxide Coating:** This is a popular finish for hex keys due to its corrosion resistance and anti-reflective properties. Black oxide-treated hex keys are suitable for general-purpose use, offering moderate protection against rust and moisture. The coating also provides a slight texture, which can improve grip and prevent slippage, particularly in oily or damp conditions.
- **Chrome Plating:** Chrome plating is a highly durable coating that offers superior corrosion resistance, making it ideal for hex keys exposed to outdoor or wet environments. This coating creates a hard, reflective surface that resists rust, moisture, and chemical exposure.
- **Nickel Plated Coating:** Nickel plating provides excellent corrosion resistance and durability, similar to chrome plating, but with a slightly different look and feel. Nickel-plated hex keys are often used in applications requiring a tough, protective layer that can withstand repeated use and contact with moisture or chemicals. The nickel finish offers a smooth, low-friction surface that makes the keys easier to insert and remove, especially from close-fitting hex socket screws.
- **Phosphate Coating:** Commonly applied in a dark grey or matte finish, this type of coating provides a moderate level of corrosion resistance and a non-reflective surface. It is often used on hex keys for automotive applications, as they excel in reducing light reflection, which can be useful in precision settings.

## **Hex Key Sizes**

### **Metric vs. Imperial Sizes**

Metric hex keys are measured in millimetres and are typically used in equipment and machinery manufactured in regions that follow the International System of Units (SI), such as Europe and Asia. On the other hand, imperial hex keys are measured in inches and are often used in the United States and other regions that adhere to the imperial system.

Choosing between metric and imperial hex keys is crucial because even slight discrepancies in size can lead to issues such as rounding or stripping of the fastener. For example, using a 5mm hex key in a 3/16” hex socket may seem close, but this small difference can easily damage the socket, especially under high torque.

### **Common Sizes and Choosing the Right Fit**

Hex keys are available in a wide range of sizes, from very small (e.g., 1.3mm or 0.5”) to larger diameters (e.g., 24mm or 3/8”). Common metric sizes include 2mm, 4mm, 5mm, and 8mm, while typical imperial sizes include 1/8”, 5/32”, and 1/4”.

Getting the correct size is essential for effective torque application. Using an undersized key risks stripping the fastener head, while an oversized key won’t fit properly. In cases where high torque is needed, such as with automotive or machinery components, having the exact size match is vital to ensure stability and minimise wear on both the tool and the fastener.

## **Using Hex Keys Correctly**

Proper use of hex wrenches enhances safety and extends the tool’s lifespan. When using a one for your application, keep the following in mind:

### **Inserting the Hex Keys**

Always ensure the hex key is fully inserted into the [hex socket screw](https://au.rs-online.com/web/c/fasteners-fixings/screws-bolts/socket-screws/) before applying force to ensure maximum surface contact between the tool and fastener, which distributes torque evenly. When only partly inserting your hex key, this can lead to slippage or rounding, especially with smaller hex keys. Furthermore, full alignment not only maximises torque but prevents damage to both the wrench and fastener.

### **Applying Torque**

For L-shaped hex keys, use the longer arm for extra leverage when loosening fasteners, as it allows for greater torque application. When tightening, switch to the shorter arm for more controlled force and reduced risk of over-torquing. 

For applications requiring a consistent amount of torque, such as in electronics or automotive work, consider using a T-handle hex key or torque wrench to achieve precise torque settings without damaging components.

### **Avoiding Over-Tightening**

Over-tightening can strip the screw socket, round off the hex key edges, or damage the [hexagon bolt fastener](https://au.rs-online.com/web/c/fasteners-fixings/nuts-washers/hex-nuts/). To avoid over-torquing, tighten only until secure. 

In critical applications where specific torque is required, a torque wrench or hex key with a torque-limiting feature can help prevent accidental over-tightening.

## **Industry Applications**

Hex keys are indispensable in numerous fields due to their versatility and reliability. Some common industry applications include:

- **Automotive:** Used for assembling and maintaining vehicle components, hex keys secure bolts and fasteners in tight spaces where precision and compact tools are essential.
- **Furniture Assembly:** Many flat-pack furniture kits include hex keys, as their small size is perfect for fitting into compact spaces, making assembly easy for consumers.
- **Manufacturing and Construction:** In both light and heavy-duty applications, hex keys are used to secure machinery components, often in hard-to-reach areas requiring tools with a small footprint.
- **Electronics:** Hex keys are commonly used in electronics for assembling small devices and accessing internal components, where traditional tools are too large or cumbersome to use.

## **Your Trusted Hex Keys Supplier & Manufacturer**

RS is a trusted supplier and distributor of high-quality hex keys in Australia, providing a comprehensive selection of hex keys and wrench sets to suit diverse needs. With options from leading brands like [Wera](https://au.rs-online.com/web/b/wera/) and [Bondhus](https://au.rs-online.com/web/b/bondhus/), we offer both metric and imperial sizes to meet industry standards across various applications.

Our range includes individual hex keys and full hex wrench sets available in multiple coatings, such as black oxide and chrome plating, ensuring durability and corrosion resistance for every environment. Whether you need standard hex keys for general use or specialty tools for professional applications, RS AU has the quality and selection to meet your requirements.

Explore our catalogue today to find the ideal hex keys, Allen key sets, and more — designed to deliver reliability and precision in every task. For more details on our delivery services, please check our [delivery page](https://au.rs-online.com/web/content/support/all-articles/delivery).



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