Select Page

GD&T Profile of a Line Definition

In GD&T, profile of a line tolerance is similar in many respects to profile tolerance.  The major difference is that profile of a line establishes a two-dimensional tolerance zone that controls individual line elements of a feature or surface.  Profile of a line is usually applied to parts with varying cross-sections, or to specific cross sections critical to a part’s function.  Examples of parts where profile of a line could be applied include aircraft wings and housings used to seal out dust or water.

An example of profile of a line tolerance is shown below.  In the left figure, profile of a line is applied to the top surface of a part.  The boxed symbols can be read "each line element of this surface at any cross section must lie between two boundaries spaced 0.2 apart relative to datums A and B".  The two right figures show sample cross-sections of the part with line elements that meet this tolerance requirement.  Note that the tolerance remains the same for the line element even though the cross-section shape is different.  Also note that two datums are needed to define the orientation of the cross section plane.

Because profile of a line can require multiple measurements at any number of cross sections, it is customary to specify the number of cross sections to be checked on the drawing. 


Was this information helpful? YES SOMEWHAT NO