What does the concentricity symbol look like?

• A. Two concentric circles
• B. A single line
• C. A triangle
• D. A parallelogram

Answer: (A)

The symbol for concentricity in GD&T is represented by two concentric circles. This visual representation signifies that features on a part must be positioned such that their centers align with a common axis or center point. The use of concentric circles clearly communicates the intention of ensuring a consistent relationship between two or more features regarding their alignment around a central point.

The concentricity symbol is particularly useful in ensuring that holes or cylindrical features are correctly aligned along the same axis, which is crucial for mechanical components that need to fit together reliably. The straightforward depiction of circles reinforces the concept of circular symmetry that the term 'concentric' embodies, making it easy for engineers and designers to interpret the requirement effectively.