Nuts, Bolts & Washers

Choosing the Right Nuts, Bolts & Washers

At County Building Supplies, we supply nuts, bolts, threaded bar and washers for builders, carpenters, tradespeople and DIY customers. Whether you're connecting timber, securing metal components or completing general construction and maintenance work, choosing compatible fasteners is essential for a reliable fixing.

Our range includes TIMCO cup square carriage bolts in various metric sizes and lengths, alongside nuts, washers and threaded bar for suitable fastening applications.

Which Type of Bolt Do I Need?

The correct bolt depends on the materials being joined, the thickness of the connection and the loads involved.

• Carriage bolts: Also known as cup square bolts, these have a rounded head and a square section beneath it. They're commonly used for suitable timber connections, including gates, fencing and timber structures.
• Hex bolts: Have a hexagonal head designed to be tightened using a suitable spanner or socket. They're widely used for mechanical connections where specified.
• Threaded bar: A continuous length of threaded metal that can be cut to a suitable length and used with compatible nuts and washers for appropriate fixing applications.

What Do M6, M8, M10 and M12 Mean?

Metric bolt sizes identify the nominal diameter of the thread. For example, M8 refers to an 8mm nominal thread diameter, while M12 refers to a 12mm nominal thread diameter.

When a bolt is described as M10 x 100mm, this generally indicates a 10mm nominal thread diameter and a 100mm bolt length. For a standard carriage bolt, length is normally measured from beneath the head.

County Building Supplies lists TIMCO carriage bolts in M6, M8, M10 and M12 sizes, with various lengths available.

What Are Carriage Bolts Used For?

Carriage bolts are commonly used for timber-to-timber and suitable timber-to-metal connections. Their rounded head provides a neat appearance, while the square section beneath the head helps resist rotation when correctly seated in an appropriate material.

They're often used for suitable gates, fencing, timber frames and other joinery or construction projects.

When choosing a carriage bolt, check the required diameter, length, thread specification and compatibility with the nut and washer.

Choosing the Right Nuts

Nuts are used with compatible bolts or threaded bar to secure mechanical connections. The nut must match the bolt's thread diameter and pitch.

Different nut designs are available for different applications, including standard hex nuts and locking types. Where vibration, movement or loosening is a concern, the appropriate locking method should be specified for the connection.

Why Are Washers Important?

Washers are commonly placed beneath a nut or bolt head to distribute contact pressure and help protect the surface of the material being fastened.

• Flat washers: Provide a bearing surface beneath a nut or bolt head.
• Large-diameter washers: Can help spread contact pressure over a larger area, particularly with suitable timber connections.
• Spring washers: Are used in certain fastening arrangements, although they should not be assumed to provide reliable vibration resistance without an appropriate specification.
• Sealing washers: Include a sealing component and are used where the fixing design requires a suitable seal.

Our online range includes TIMCO Dowty washers for suitable sealing applications.

Bright Zinc Plated vs Galvanised Fasteners

Fasteners are available with different protective finishes depending on their intended use.

Bright zinc plated (BZP) bolts have a relatively thin zinc coating that provides a degree of corrosion protection and is commonly used for suitable internal or sheltered applications.

Hot-dip galvanised fasteners generally have a thicker protective zinc coating and can offer greater corrosion resistance in appropriate external environments.

For exposed outdoor applications, treated timber or demanding environments, check the manufacturer's corrosion-resistance specification rather than assuming all zinc-coated products provide the same protection.

How to Choose the Correct Bolt Length

When selecting a bolt, consider the combined thickness of the materials being joined, the washers being used and the nut engagement required.

The bolt should be long enough to accommodate the complete connection and achieve the required thread engagement, without being unnecessarily long for the application.

For structural or load-bearing connections, follow the relevant design and manufacturer's fixing specifications, including bolt grade, diameter, spacing and tightening requirements.

Need Advice?

If you're unsure which nuts, bolts or washers you need, visit your local County Building Supplies branch or contact our team. Tell us what materials you're joining and the dimensions or specifications you require, and our team can help you find suitable products from our range.