ANSI Line Conventions and Lettering

The level of detail in these representations often varies for the intended audience. Sometimes the intent is to show the general design to a client, so details may be left out of the representation so as to focus on the global project issues. Other times, the graphical representation may be used for a machinist or construction worker who needs exact dimensions and tolerances in addition to production/construction information for producing the part or artifact. 

Visible lines are solid thick lines that are used for representing visible edges or contours of objects. Hidden lines are short, evenly spaced thin dashes that depict the hidden features of an object. Section lines are solid thin lines that indicate the cut surfaces of an object in a section view. Special lining symbols are sometimes used to indicate the type of material depicted. 

Solid thin lines used for dimensioning include (1) dimension lines, which indicate the extent and direction of dimensions (2) extension lines, which indicate the point or line on the drawing to which the dimension applies and (3) leaders, which direct notes, dimensions, symbols, item numbers, or part numbers to features on the drawing. 

Phantom lines are used to indicate alternate positions of moving parts, adjacent positions of related parts, and repeated detail. Phantom lines are shown as long thin dashes separated by pairs of short thin dashes. 

AMERICAN NATIONAL STANDARDS INSTITUTE LINE CONVENTIONS AND LETTERING 

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