Center lines are an important element of engineering drawings that are used to represent the axis of symmetry for a part or assembly. These lines are drawn as long, thin dashed lines and are used to indicate the center point of cylindrical features, such as holes or shafts. Center lines are used to help ensure that features are aligned properly, and are often used in conjunction with other types of lines and dimensions to communicate critical design information to the manufacturing team. In ASME Y14.2, there are specific conventions and guidelines for drawing center lines that ensure consistency and clarity in engineering drawings.
Center lines extend a short distance past the edges of the feature they describe and they should not extend across views. They should not start or end at other lines. Center lines may be extended as necessary for dimensioning purposes.
