Nominal diameter and bore diameter

This post was last edited by ylb913 on 2016-6-23 21:18. The nominal diameter comes in series and is standardized. The actual passage size depends on its outer diameter and wall thickness; in fact, there are also series for this, but they are not standardized.

The nominal diameter is the dimension of all piping fittings in a piping system, expressed as a number. It is a convenient round integer for reference only, and it has only an approximate relationship with the actual manufacturing dimensions. The nominal diameter is indicated by the letter “DN” followed by a number. Such as PVC water supply pipes and galvanized water supply pipes: DN40, DN50, DN65. The nominal diameter is also known as the average outer diameter. This is because the wall thickness of many tubes is very thin, and the outer diameter and inner diameter of the tube are almost identical; therefore, the average of the outer and inner diameters is used as the value representing the tube diameter. In engineering, \"bore\" generally refers to pipes within a certain diameter range; for example, a pipe with a bore of 15 corresponds to pipes with an outer diameter of 22 or 20, across various wall thicknesses such as 0.4, 0.5, 0.6, 0.8, 1.0, 1.2, 1.4, 1.5, 1.6, 1.8, 2.0, 2.5, 2.8, etc. Here, the bore denotes pipes within a specific range, rather than the average of the outer and inner diameters. For reference only!