Why is Profile of a surface used?
A casting can satisfy sparse point dimensions yet interfere with a mating cover between them.
PROFILE CONTROL / GD&T SYMBOL GUIDE
PROFILE OF A SURFACE
Profile of a surface controls the full three-dimensional surface within a zone around its theoretically exact shape. Use it when the whole surface matters; profile of a line controls individual cross-sectional line elements. Datum references can also establish orientation and location.
INTERACTIVE APPLICATION
GD&T profile of a surface example: cast housing face
NO SEPARATE CONTROL
Local dimensions miss surface-wide variation
- No separate profile of a surface requirement is stated for this cast housing face.
Limitations
- A casting can satisfy sparse point dimensions yet interfere with a mating cover between them.
- High spots can obstruct assembly or sealing.
PROFILE OF A SURFACE CONTROL
The full face follows one profile zone
- The complete surface must remain inside the 0.30-wide zone between two offset 3D boundaries.
- Basic geometry defines the intended shape; datum A establishes the referenced orientation or location.
Advantages
- The complete surface is checked against the design shape.
- The drawing states the intended requirement for inspection and assembly.
Where is Profile of a surface used?
Cast housings, moulded covers, aerodynamic skins and complex machined faces.
How is Profile of a surface used?
Define the nominal surface with basic geometry, identify its extent and attach the profile frame. Establish datum A before inspection in this example.
The double-ended arrow indicates the total 0.30 tolerance-zone width. The two offset boundaries extend across the whole 3D surface, rather than one cross-section.
How it is used
Define the nominal surface with basic geometry, identify its extent and attach the profile frame. Establish datum A before inspection in this example.
How to read the annotation
Read the profile of a surface symbol first, then the 0.30 tolerance in the drawing units. Datum A establishes the referenced orientation or location. Follow the frame leader to the controlled cast housing face.
Commonly defined variable values
The controlling value is a tolerance-zone width, not a universal process grade. For this profile of a surface example, the drawing states the controlled feature and applicable extent.
Scroll the table sideways to see every column.
| Application | Illustrative starting value | Example feature | Notes / caution |
|---|---|---|---|
| Cast Housing Face | 0.30 mm | cast housing face | Illustrative only; validate coverage and point spacing. |
These are planning examples, not universal rules or guaranteed process capabilities. Set the actual tolerance from function, size, length, process capability, inspection method and the standard specified on the drawing.
Line profile vs surface profile: which one to use?
Profile of a line controls individual cross-sectional line elements. Use it when the requirement is checked section by section, such as an extruded rail contour.
Profile of a surface controls the whole 3D surface. It is normally the right choice when the complete face, including its width and depth, must meet the specified zone.
Explore profile of a line →How is profile of a surface measured in real life?
Establish datum A first. Measure the indicated feature and compare it with the requirement shown on the drawing.
- CMM: Sample an appropriate surface grid and compare it with the basic model from the stated datums.
- 3D scan: Use a calibrated scan and suitable alignment for accessible surfaces.
ASME Y14.5-2018 (R2024)
ASME Y14.5 surface profile controls the indicated surface, with datum references affecting its orientation and location.
ASME Y14.5 edition reference. Examples are learning schematics; use the complete requirements on the drawing.
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