If you’re in the market for fasteners or working on a project that requires screws, it’s important to know how to identify the correct size. Screws are sized by their diameter and thread count, which helps ensure they have the strength to hold your project together. In this article, we’ll walk you through the process of measuring your screw diameter and thread count so you can find exactly what you need.
First, you’ll need to decide whether you’re dealing with standard inch-based screw threads or the metric system that is becoming increasingly popular in the United States and elsewhere. Screws in the US are typically measured according to a system called the Unified Thread Standard (UTS). This uses a numbering system with a combination of gauge and threads-per-inch measurements. Screws are also rated by their head diameter and length, which you can measure with a set of calipers.
In this system, the first number in a screw size indicates the screw’s gauge. This number corresponds to the width of a single thread, or its major diameter. The second number is the number of threads per inch, or TPI. You can measure the TPI by counting the number of peaks on a one-inch section of the screw threads. The number of TPI is then multiplied by the screw’s major diameter to give you the thread size.
The UTS screw size system also divides its standard thread sizes into coarse and fine series. The coarse threads are more commonly used, while the fine threads offer a more secure fit for delicate materials like wood. In addition, the UTS screw size system has different types of head threads as well.
While it may seem confusing at first, identifying the right screw size for your project isn’t difficult once you understand the different measurements used. The good news is, there are handy reference charts available that help you determine the correct screw size for any given application. These charts also have the equivalents in the metric system, which can be useful when purchasing fasteners overseas.
There are several different methods for determining screw and bolt sizes, but the most common is to use the screw chart, which shows the standard thread size in both inch and metric formats. The chart identifies the screw gauge, the threads-per-inch measurement, and the head diameter in both metric and imperial units. The chart also includes a conversion table for converting between screw gauges and decimal numbers.
When sizing screws in the US, the decimal equivalent of a screw gauge is listed as the first number on the chart. The chart also gives you the decimal equivalents for screw gauges in mm, so that you can match your metric drill bits to the appropriate screw sizes. In addition, the chart provides the head diameter and length of a screw in both inch and metric units. This makes it easy to shop for the exact type of screw you need for any job. screw size chart