Use a steel tubing chart to identify tubing for a specific project by size. For round tubing, outside diameter (OD) is provided in inches as are the height and width for square or rectangular tubing. The thickness of the tube wall is also provided in inches or by gauge.
Thickness gauges range from 7, the heaviest, to 22, the lightest. Some steel tubing charts also include the interior diameter (ID) and the weight in pounds per foot. Manufacturers provide a variety of tubing charts by unit of measurement or type of steel or tubing, such as fractional or metric gauge charts and 304/316-grade or seamless tubing.
Choose the chart that aligns with the project in terms of measuring unit and composition. Grade tubing that is 304/316 is an alloy most often used for medical purposes, processing foods or refining oil. Seamless tubing is used in situations where there is likely to be high pressure and high probability of corrosion. Steel composition and wall thickness required varies based on how the tubes are manipulated, for example, depending on the types of bends or welds required. Steel tubing and steel pipes are used for different purposes and are sized differently according to that purpose.