The Ultimate Guide to Screws

When it comes to screws, the variety available can be overwhelming. Understanding the different characteristics of screws will help you choose the right one for your specific project. In this guide, we will break down all the parts of the various screw types offered on BOLTS.co.uk. 

Material

The material of a screw is crucial as it determines the screw's strength, durability, and resistance to environmental conditions. Here are the common materials used in screws:

• Steel: Steel screws are the most common and versatile. They are strong and suitable for general use.
• Stainless Steel: These screws are corrosion-resistant and ideal for use in environments exposed to moisture or chemicals. There's also different types of stainless steel options available - check out the difference between A2 & A4 stainless steel here.
• Brass: Brass screws are used for their aesthetic appeal and corrosion resistance. They are often used in marine and electrical applications.
• Aluminium: Lightweight and corrosion-resistant, aluminium screws are used where weight is a concern and moderate strength is sufficient.

Finish

The finish on a screw not only affects its appearance but also its resistance to corrosion and wear. Common finishes include:

• Zinc Plating: Provides a layer of corrosion resistance and is commonly used for general-purpose screws.
• Black Oxide: Adds a mild layer of corrosion resistance and reduces glare, often used for aesthetic purposes.
• Galvanized: A thick zinc coating that offers superior corrosion resistance, ideal for outdoor and high-moisture environments, the ideal finish for decking screws.
• Chrome: Provides a shiny, decorative finish along with good corrosion resistance.
• Phosphate: A matte finish that provides good lubrication and corrosion resistance, often used in drywall screws.

Gauge

The gauge of a screw refers to its thickness or diameter. It is an important attribute as it determines the strength and load-bearing capacity of the screw. The gauge is typically indicated by a number, with higher numbers indicating thicker screws. 

Head Type

The head type of a screw affects how it sits in the material and the tool required to drive it. Here are some common head types:

• Flat Head: Designed to sit flush with the material surface, ideal for countersinking.
• Pan Head: Has a slightly rounded, low-profile head that sits above the surface.
• Round Head: Fully rounded head, used where a protruding head is acceptable.
• Hex Head: Six-sided head for use with a wrench or socket.
• Socket Head: Cylindrical head with a hexagonal drive hole, used in machine screws.

Check out our screw head types guide for more information.

Thread Type

Threads are the helical ridges around the body of the screw that allow it to bite into materials. Thread types include:

• Coarse Threads: Fewer threads per inch, suitable for soft materials and quick assembly.
• Fine Threads: More threads per inch, providing greater holding power in hard materials.
• Machine Threads: Uniform threads used with nuts or pre-tapped holes in metal.
• Thread Forming Screws: These screws form threads during insertion, usually in metal, to eliminate the need for thread tapping as a separate process.

For a detailed guide on thread types, check out our comprehensive thread type guide.

Point Type

The point type of a screw determines how it starts into the material. Common point types include:

• Sharp Point: Standard point for most screws, ideal for soft materials.
• Self-Drilling Point: Has a drill-like tip for creating its own hole in metal and wood, reducing the need for pilot holes.
• Blunt Point: Used in applications where a sharp point might damage the material.

Number

The number on a screw, often confused with the gauge, usually refers to the size designation used in certain standards (e.g., #6, #8, #10 in the US). This number can help identify the screw's diameter and thread count.

Total Length vs. Length Under Head

When specifying the length of a screw, it is important to distinguish between:

• Total Length: The entire length of the screw from the tip to the top of the head.
• Length Under Head: The length of the screw excluding the head, which is particularly important for screws with countersunk heads.

Self Tapping vs. Self Drilling

Self-tapping and self-drilling screws offer unique benefits for specific applications:

• Self Tapping: These screws create their own threads as they are driven into the material. They are ideal for materials like plastic, wood, and thin metal.
• Self Drilling: These screws have a drill-like tip that allows them to cut their own hole and create threads in one operation, making them suitable for thicker materials and metal-to-metal fastening.

By understanding these attributes, you can choose the right screw for your project, ensuring optimal performance and durability. Explore the wide variety of screws available at BOLTS.co.uk and find the perfect match for your needs.