Understanding Sheet Metal Screw Sizes: A Comprehensive Guide

Sheet metal screw sizes are categorised by head styles and three numbers that represent the screw's diameter, length and thread count. The diameter, or sheet metal screw size, is indicated by a number between zero and 24, with the most common sizes ranging from 6 to 14. The length is measured differently depending on the head style of the screw. For flat or bugle heads, the entire length of the screw is measured, while for other head styles, the length is typically measured from underneath the head to the point. Each fastener also has a pitch that indicates the number of threads per inch of its length. For example, a screw labelled 8-14x1 is a size 8 screw with 14 threads per inch and is 1 inch long.

Common Sheet Metal Screw Sizes

Sheet metal screw sizes are indicated by numbers between #0 and #24

The diameter of a screw is an important factor in determining its load-bearing capacity. Larger diameter screws generally have higher load-bearing capacities due to their increased surface area and strength. This is particularly important in construction and engineering applications, where the integrity and safety of structures depend on the proper selection and use of fasteners.

In addition to the diameter, sheet metal screws are also categorized by their length and thread count. The length of a sheet metal screw is measured differently depending on the head style. For flat or bugle heads, the entire length of the screw is measured since it will be completely embedded in the material. For other head styles, the length is typically measured from underneath the head to the point.

The thread count of a sheet metal screw refers to the number of threads per inch of the fastener's length. This is also an important factor in determining the screw's strength and suitability for a particular application. For example, a screw with a higher thread count will generally have greater holding power and may be more suitable for applications where vibration is a concern.

Sheet metal screws are available in different point types, including Type A, Type AB, and Type B. Type A screws have coarse threads and gimlet points, and are used for thin metals and wood. Type AB screws are similar to Type A but have finer threads, making them suitable for more fragile materials. Type B screws have blunt tips and spaced threads, making them appropriate for plastics, plywood, and thin metals.

By understanding the sizing and variations of sheet metal screws, users can make informed decisions when selecting the appropriate fasteners for their projects.

The most common sheet metal screw sizes are #6 to #14

Sheet metal screws are used to fasten metal pieces to other metal objects or to attach metal to another surface, such as plastic, aluminium, plywood, hard rubber, or wood. They are fully threaded to increase retention between materials and have sharp tips and threads to help pierce solid metal surfaces and other sturdy materials.

Sheet metal screws are categorised by head styles and three numbers that represent the screw's diameter, length, and thread count. The diameter, or sheet metal screw size, is indicated by a number between zero and 24 to describe the shank, with the most common sizes used by contractors and OEMs being #6 to #14. The length is measured differently depending on the head style of the screw. For flat or bugle heads, the entire length of the screw is measured since it will be embedded entirely in the material. Each fastener also has a pitch that indicates the number of threads per inch of a fastener's length. For example, a screw that reads 8-14×1 indicates it is a size 8 with 14 threads per inch and is 1 inch long.

Sheet metal screws are available in three point types. Type A screws have coarse threads and gimlet points used in thin metals and wood. Type AB is a fine-thread screw, also with gimlet points, and is ideal for more fragile materials. Type B has blunt tips and spaced threads for plastics, plywood, and thinner metals.

Self-tapping sheet metal screws are ideal for jobs with pre-drilled holes. They have sharp tips to drive the screw through the metal, and the technique of using a pilot hole helps prevent the splitting of the material, creating a more seamless finish. Self-drilling sheet metal screws, on the other hand, have a tip that is more like a drill point to penetrate metal without the need for a pilot hole. They help preserve the integrity of the material by avoiding denting.

Sheet metal screws are categorised by head styles and three numbers

Sheet metal screws are used to fasten metal pieces to other metal objects or to attach metal to another surface, such as plastic, aluminium, plywood, hard rubber, or wood. They are fully threaded to increase retention between materials and have sharp tips and threads to help pierce solid metal surfaces and other sturdy materials.

The head styles of sheet metal screws include flat, hex, hex washer, oval, pan, and truss. A flat head has a Phillips or slotted style that provides an ideal countersink for various materials, meaning it rests below the surface. A hex head has a hexagonal shape that is often used with a nut to create a secure attachment. A hex washer head, also called a bugle head, has a hexagonal head and a washer to secure the screw's shank to the material. An oval head is similar to a flat head but has more girth on top to provide a finished look. It sits flush against a surface to reduce wind resistance and enhance installation. A pan head is rounded and protrudes above the surface when installed. It can have a Phillips or slotted-head variation and may be zinc-coated or coated in stainless steel, white, or black. A truss head has a wider head and a rounded top with a Phillips-style slot.

Sheet metal screws are available in three point types: Type A, Type AB, and Type B. Type A screws have coarse threads and gimlet points, and they are used in thin metals and wood. Type AB is a fine-thread screw with gimlet points, making it suitable for more fragile materials. Type B screws have blunt tips and spaced threads, making them ideal for plastics, plywood, and thinner metals.

Sheet metal screw diameter is measured in inches or millimetres

Sheet metal screw sizes are categorised by head styles and three numbers that represent the screw's diameter, length, and thread count. The diameter, or sheet metal screw size, is indicated by a number between zero and 24 to describe the shank, with the most common sizes used by contractors and OEMs being 6 to 14. The length is measured differently depending on the head style of the screw. For flat or bugle heads, the entire length of the screw is measured since it will be embedded entirely in the material. For all other sheet metal screw head styles, such as hex, pan, round, and truss, the length is measured from under the head to the screw's tip.

Sheet metal screws are typically #2 to #14 in diameter, with some head styles also available in 5/16" and 3/8". The diameter of a screw is defined by a proportionate number from 0-24, not by its length. A size-8 screw, for example, has double the shank diameter of a size-4 screw. To get the actual diameter, add 0.060 inches to the screw size.

The metric system uses millimetres to measure screw sizes, whereas the imperial system uses a "gauge" table. The length of a screw in both systems is expressed in millimetres or fractional inches, respectively. The gauge of an imperial screw does not directly relate to the head size. However, some sources claim that the gauge is almost double the diameter of the head of a screw gauge 6 and above.

Sheet metal screws have been used since the early 1900s for metallic and non-metallic materials too thin to tap. They are often called thread-forming screws because they "tap" their internal mating threads by forcing material outward, creating a tight fit that won't loosen. They are fully threaded and not tapered, unlike wood screws, and are available in various materials such as standard steel, stainless steel, and zinc-plated galvanised screws.

Sheet metal screws are used for fastening metal to other surfaces

Sheet metal screws are categorised by head styles and three numbers that represent the screw's diameter, length, and thread count. The diameter, or sheet metal screw size, is indicated by a number between zero and 24, with the most common sizes used by contractors ranging from 6 to 14. The length is measured differently depending on the head style of the screw. For flat or bugle heads, the entire length of the screw is measured since it will be embedded entirely in the material. Each fastener also has a pitch that indicates the number of threads per inch of a fastener's length. For example, a screw labelled 8-14x1 is a size 8 screw with 14 threads per inch and is 1 inch long.

Sheet metal screws are typically made of stainless steel, which aids in durability and long-term performance. However, not all sheet metal screws are made of stainless steel, and other materials are available. 410 stainless screws (magnetic) without a protective coating are called passivated, while those with a protective coating have extra protection against surface rust formation over time.

The two main types of sheet metal screws are self-tapping and self-drilling. Self-tapping screws are ideal for jobs with pre-drilled holes and have sharp tips to drive the screw through the metal. Self-drilling screws, on the other hand, have a tip similar to a drill point, allowing them to penetrate metal without the need for a pilot hole. Both types of screws offer advantages in terms of installation speed, corrosion resistance, and versatility.

Sheet metal screws are available in different point types, including Type A, Type AB, and Type B. Type A screws have coarse threads and gimlet points, making them suitable for thin metals and wood. Type AB screws are similar but feature finer threads, making them ideal for more fragile materials. Type B screws have blunt tips and spaced threads, making them suitable for plastics, plywood, and thinner metals.

Frequently asked questions