Screws are used for a wide variety of construction tasks, from woodworking to metal roofing. They come in a multitude of lengths and widths to suit any application, but choosing the wrong type can cost time and money, so it’s important to know how to measure and select the right screws for your project. While it’s not as simple as grabbing a nail and hammering it in, measuring screws is much more straightforward than many assume – and it comes down to three essential measurements: gauge, length, and threads per inch (TPI).
Screw sizes are typically labeled with a callout number that includes the screw’s major diameter and its pitch, which indicates how far each thread extends from one end of the screw to the next. However, the callout numbers can be difficult to decipher, especially if you’re unfamiliar with screw sizing terminology. Luckily, HouseholdQuotes has put together this article to help make it easier to understand the different measurement formats and their associated specs.
Generally speaking, most wood screws are listed with their major diameter and length. The length will usually be expressed as an imperial fraction and the major diameter will be expressed in decimal form. However, it’s not uncommon to see metric-only measurement callouts as well, which can be even more confusing for those unfamiliar with metric screw sizing.
When it comes to selecting the best screw for your project, you should always consider the intended purpose of the screw and how it will be used. Screws are available in a wide range of head types, so it’s important to choose the right one for your specific needs. For example, a screw with a rounded head (also known as a countersunk screw) is best for anchoring into a wood surface. A square-drive screw, on the other hand, is better suited for fastening materials that require more force.
If you’re looking for a specific screw size, you should be able to find it using a screw sizes chart. The chart will include the major diameter, the head diameter, and the length – all of which you can use to determine the proper screw for your project. The screw sizes chart also includes information on the screw’s pitch and type if you’re using a metric screw.
The screw size is the first number in the imperial callout, followed by the screw’s length. The major diameter is the largest dimension of the screw, and the pitch is the distance between each thread on the screw. Screws sold in the US are typically labeled with both the major diameter and the screw pitch, whereas screws sold in Europe are often only labeled with their major diameter.
The screw’s pitch is represented by the second number in the metric callout. The number will indicate the distance between each screw thread, which is sometimes separated into two columns: one for coarse screw threads and one for fine screws. For example, a 10 mm screw has a thread pitch of 1.5 mm. screw sizes chart