A Complete Guide to Hex Bolts

What are Hex Bolts Used for?

Hex head bolts are versatile and adaptable fasteners, making them suitable for a variety of uses across a range of industries and applications. Example hex bolt uses include hex head screws for wood, metal, and many other environments and scenarios.

They offer strong tensile properties and most standard types can be used in multiple locations (dependent upon the material and finish). As a result, hex bolts are a widely used staple fastener.

Their primary use is for heavy-duty fixing and fastening applications. This could include:

• Within construction projects

• During the erection, repair, and maintenance of buildings, bridges, and road infrastructure

• Machinery assemblies

• Woodworking tasks such as fastening frames

• Engineering applications

• Vehicle and automotive

Types of Hex Bolts

Various different types of hex bolts are available, each best suited to different applications and environments. Hex bolts can be categorised in a number of different ways – chiefly their sizing, the material or finish used in their manufacture, and whether they are fully or partially threaded.

The following sections provide further detail on some of the key hex bolt types, giving you the knowledge you need in order to make a fully-informed buying decision.

Hex Bolt Threading

The thread of a hex head bolt, also known as the screw thread, is the helical structure which comprises the main body of the bolt. It uses rotational force to drive the bolt firmly and securely into place, helping to provide easier entrance and exit into the material whilst also providing added grip. Both fully-threaded and partially-threaded hex bolts are available.

Hex Bolt Materials

Hex bolts are typically manufactured from steel or stainless steel. While some manufacturers offer hexagonal bolts made from other materials, steel and stainless steel hex bolts are the norm.

Additionally, different coatings and finishes are available. These provide various qualities and appearances in order to suit a wide range of applications.

Popular hex bolt finishes include:

• Bright zinc-plated

• Zinc hex bolt

• Clear passivated

• Black oxide

• Plain

Hex Bolt Sizes

Choosing the right-sized hex bolt for your task is important, and there are several factors to take into consideration when measuring hex bolt dimensions and sizes. These are as follows:

• The length of the bolt (measured from the end of the bolt up to under the head)

• Thread size (the size of the thread, typically using ISO metric or M-style measurements)

• Thread pitch (the number of threads per inch – the finer the bolt, the more threads per inch and the higher the thread pitch)

The ISO metric thread size system is widely used around the world. It is a handy international standard for measuring thread sizes across an array of different screw and bolt types. Each size is denoted by the letter ‘M’ followed by a number. This number indicates the outer diameter of the thread, measured in millimetres. As an example, a hex bolt with a thread size of M8 would have an outer diameter of 8mm.

Click through to shop some of the most common hex bolt thread sizes:

Hex Bolt Size Chart

Most hex bolt size charts refer to a specific range of products. As a result, it can be difficult to locate an accurate chart which covers a range of hex bolt types and sizes. The following hex bolt size charts should help you to easily select the most suitable product for your requirements.

DIN Standard 931 Hex Bolt Size Chart

This size chart focuses on DIN standard 931 bolts (hex bolts which have a partially-threaded clear shank along the length of the body).

DIN Standard 933 Hex Bolt Size Chart

This additional size chart is intended for use with DIN standard 931 bolts (hex bolts which have a completely threaded shank).