Geometric Tolerances Orientation Profile any line
The profile of a line is an orientation tolerance that defines how accurately an individual cross-sectional line of a surface follows the intended geometry in a given plane. It differs from angularity, perpendicularity, and parallelism in that it allows you to control the accuracy of lines for more complex shapes—not just straight angles or directions.
The tolerance zone is formed between two ideal profile lines, spaced apart by the tolerance value given in the drawing. All points of the actual shape must lie within this zone. If the tolerance references a datum, the profile line is related to it; if not, it controls the line independently.
Applications
- Curved and beveled shapes: ensures that the line closely follows the intended geometry, for example in contoured surfaces or cast parts.
- Aerodynamic structures: the profile of a line can specify the accuracy of a surface that affects drag.
- Aesthetic features: controls the precise appearance of visible surfaces.
Notating in drawings
The profile of a line is indicated in a geometric tolerance frame with the profile symbol ∩ and the specified tolerance value. For example:
| ∩ | 0.2 | A |
This means that the points of the cross-sectional line of the actual surface must fit within a 0.2 mm wide tolerance zone relative to datum A.
Significance in manufacturing
The profile of a line is a highly useful tolerance, as it allows for flexible control of even complex shapes. If the line’s shape deviates too much, parts may not fit together properly or may suffer in terms of function, such as with airflow or connections. However, a tolerance that is too tight increases manufacturing costs, since it requires precision machining and measurement, such as by a coordinate measuring machine (CMM).
The profile of a line per ISO 1101 provides designers with a way to control the accuracy of a feature so that the part works in practice, while keeping manufacturing cost-effective.
