What is the purpose of a center line on a blueprint?

What is the purpose of a center line on a blueprint?

• A. Locate the center of a cylindrical part or feature
• B. Show surface roughness
• C. Indicate material specification
• D. Mark part origin

Answer: (A)

Center lines indicate the axis of symmetry or the center axis of cylindrical features on a drawing. They provide a reference for locating centers, holes, and other round features, which is essential for aligning machining operations (like turning, drilling, or boring) and for accurate dimensioning and inspection. This is why locating the center of a cylindrical part or feature is the best description of their purpose. They aren’t used to show surface roughness (that uses a roughness symbol and value), they don’t specify material (that’s shown in notes or a bill of materials), and they don’t by themselves mark the part origin (datum references handle that role).

Center lines indicate the axis of symmetry or the center axis of cylindrical features on a drawing. They provide a reference for locating centers, holes, and other round features, which is essential for aligning machining operations (like turning, drilling, or boring) and for accurate dimensioning and inspection. This is why locating the center of a cylindrical part or feature is the best description of their purpose.

They aren’t used to show surface roughness (that uses a roughness symbol and value), they don’t specify material (that’s shown in notes or a bill of materials), and they don’t by themselves mark the part origin (datum references handle that role).