Profile of a Surface

The profile of a surface specification defines a 3-dimensional tolerance zone equidistant from the theoretically exact shape or curve (i.e. the “True Profile”) to control all the points along the surface to be within a tolerance range.

Profile of a Surface Symbol:

GD&T symbol Profile of a Surface

Profile control is a very important aspect in all designs wherein irregular, curved or complex geometries are necessary (common in ergonomic and aerodynamic designs). For example, an airplane wing requires the proper shape to ensure consistent function. You can either use the profile of a surface with datum references or without, depending on the functional requirements for the design.

Profile of a surface is a GD&T symbol used with datum if you want to control every aspect of a feature’s geometry like size, shape, orientation, and even location . Practically, profile of a surface can be checked with a CMM that can measure the actual, as-produced surface compared to the theoretically exact surface (True profile). A CMM can compare the 3D scan of the as-produced surface to the dimensions on the drawing or directly to the CAD model to see if that surface is within the specified tolerance. If you have a simple shape, you may be able to make use of a height gauge and other hand tools along the surface of the feature to see if it’s within the requisite profile tolerance range.

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