What is the purpose of cutting-plane lines in a technical drawing?

Cutting-plane lines serve a specific function in technical drawings, primarily to indicate sections for imaginary cuts. These lines are drawn to illustrate where a hypothetical cut is made through a part, allowing the viewer to understand internal features that are not visible from the exterior. When a cutting-plane line is indicated, it typically leads to a detailed view or section view that reveals the internal geometry, aiding in the interpretation of complex shapes or assemblies.

This practice is crucial for manufacturers and engineers as it provides a clear understanding of the object’s structure, showing elements like holes, cavities, or features that cannot be adequately communicated through external views alone. By using cutting-plane lines, designers ensure that the necessary details are conveyed to facilitate proper manufacturing or assembly processes.