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Used across almost all industries, screws and bolts are an essential piece of kit to have on hand at all times. Coming in many shapes, sizes and types, screws and bolts are a simple, convenient yet highly effective form of fastening. Here at Cromwell, we have a range of screws and bolts from our trusted own brands Qualfast and Matlock as well as from market leading brands TTC Lifting, Spax® and Thomas Smith Fasteners.

What are screws and bolts?

Screws and bolts refer to the broad category of fasteners that are designed for attaching two materials or objects together via a threaded body. Whilst the terms are often used interchangeably, the key difference between them lies in their thread design and fastening type. Screws generally possess a tapered thread and have the capability of creating their own thread in a material as they are drilled. Bolts however, are designed to be turned into a pre-existing threaded hole and are to be used in combination with a nut and washer for a secure grip.

Why screws and bolts?

The main reason for selecting screws and bolts for your fastening needs is their versatility. They come in various shapes, sizes, materials and styles to ensure that no matter your application, there is a screw or bolt that fits. They are also readily available, common products that are both cost and time efficient, saving you money and time in use.

When are screws and bolts used?

Screws and bolts are a staple of any well rounded tool kit, for both the professional and DIYer. Used in almost all industries including construction, manufacturing, automotive, carpentry and engineering to name a few, screws and bolts are an effective and efficient way of securing components, materials and objects together. Unlike nails, they can easily be removed via a screwdriver whilst still providing a firm and secure hold.

Screws and bolts types

There are numerous, varied types of both screws and bolts. They vary in their size, material, shape and general function. Below, we've outlined and explained the most common eight types of screws and bolts, making it simple for you to make an informed purchasing decision.

• Hex bolts   -   Often referred to as hex cap screws, hex bolts are characterised by their six sided head which requires a spanner or wrench to tighten. They can be either fully or partially threaded and have a flat end, suited for fastening into a pre-existing threaded hole.

• Socket screws   -   With a deep set head, socket screws are designed with a hexagonal drive, making them suited for use with a hexagonal - Allen - key or wrench. They are ideal for use in confined spaces, where a conventional screwdriver may not be adequate for driving.

• Set screws   -   Also referred to as grub screws, these are easily distinguished from other types of screws and bolts due to their shape. They are threaded along their entire length, possess a flat end and have no screw head, making them ideal for applications where a flush finish is required. They are designed to be driven into pre-existing holes.

• Eye bolts   -   This type of bolt is designed for use when securing cables or ropes that form part of a pulley system. They are characterised by their flat ends and even thread, finishing with a circular looped head in which to insert cables, providing a guide to stop ropes and cables from being left hanging loosely.

• Machine screws   -   These screws have a flat tip and are designed to be drilled into pre-existing threaded holes when clamping two parts of machinery together. They also possess a uniform thread, unlike other screws which have tapered threads and are generally tightened with a nut.

• Roofing bolts   -   Characterised by their large surface area head, roofing bolts are suited for bearing heavier loads than some other bolts, making them ideal for use when attaching thinner materials together. They also possess a flat end are designed for insertion into a pre-existing threaded hole.

• Security screws   -   Commonly referred to as tamper-proof screws, security screws are designed with a unique driving head, making it more difficult for them to be removed with a commonly shaped screwdriver.

• Self drilling screws   -   As suggested in the name, self drilling screws are designed to be bored into a material without the need for a pilot hole. They feature a tip shaped similarly to a drill bit, allowing for efficiency when driving.

Considerations when choosing screws and bolts

• Material - Whilst the majority of screws and bolts are manufactured from steel as standard, they can also occasionally be made from brass, nylon, titanium or iron. It's best to consider which material would be best for your specific application.

• Application - There are various types of both screws and bolts as outlined above. Ultimately, the right screw or bolt for you depends on the intended application. Once you have established exactly what purpose you wish the screws and bolts to serve, the material you will be working with and the features that you require of the screw, you will be able to select the right type of screw or bolt.

• Size - The size of your screw or bolt will depend upon the size of your desired hole. Some screws and bolts require a hole to be pre-threaded, so this will need to be taken into consideration when purchasing. Screws and bolts are measured by their thread size and length.

• Protective coating - In order to bolster the longevity of the screw or bolt, a protective coating such as zinc is sometimes applied. It's best to consider whether this is something you deem necessary depending on where the screw or bolt

Screws and bolts jargon buster

We want to make it easy for you to browse and shop our range of screws and bolts, so here are some key terms that will help you understand the range and their applications a little better.

What do the thread types BA, BSF, BSW, UNC and UNF mean?

The above acronyms stand for various measuring systems and standards to help you correctly identify the screw or bolt you need. Below, the acronyms are defined to help you shop our range with ease.

• BA - British Association screw thread. These were standardised in 1903 and are stylised in sizes as such: 0BA, 1BA, 2BA etc. where the bigger number denotes a smaller screw size. They are mainly still used in the railway and aerospace industries.

• BSF - British Standard Fine screw thread. This was posited as a fine pitch alternative to the BSW thread described below. They are widely used in automotive and other machinery based industries and applications.

• BSW - British Standard Whitworth screw thread. Established in 1841, this is an imperial based screw standard and was the first thread standard of its kind on a national scale.

• UNC - Unified Coarse screw thread. This is part of the UTS (Unified Thread Standard) which is commonly used in Canada and the United States. This is comparable to the ISO Metric Threaded standard of screws.

• UNF - Unified National Fine screw thread. Similarly to the distinction between BSF and BSW screws, UNF screws are the fine threaded sibling to UNC screws.

FAQs

What screw is best in plasterboard?

Also known as drywall screws, there are a specific type of screws designed for driving into plasterboard. They are a type of self tapping screw and are available with various threads such as coarse and fine depending on what material you are attaching to plasterboard.

What screw is designed for use with wall plugs?

Generally, you can use any screw in a wall plug, but the more coarse the thread, the better the grip. It's always best to make sure you pair the right size screw with the right size wall plug to ensure a firm and secure grip.