How do you measure SAE flange fittings?

SAE flange fittings are measured by their nominal size, which corresponds to the diameter of the pipe they are designed to fit. Additionally, the flange dimensions, such as the bolt hole diameter, bolt circle diameter, and thickness, are specified according to SAE standards. It's essential to use calipers or a micrometer for precise measurements, particularly for the flange face and the sealing surface to ensure a proper fit. Always refer to the relevant SAE specifications for detailed dimensional requirements.