Section views are used when hidden lines make a mechanical drawing difficult to understand. Instead of forcing the reader to mentally reconstruct internal geometry, a section view shows the component as if part of it has been cut away.
Full Section
A full section passes the cutting plane completely through the object. It is useful for housings, manifolds, shafts with internal bores, and other parts where internal geometry is the main information.
Half Section
A half section combines an external view and a sectional view. It is especially useful for symmetric components such as turned parts, housings, and rotating assemblies because the outside and inside can be understood in one view.
Offset Section
An offset cutting plane changes direction to pass through several important features that are not aligned on a single straight plane. The resulting section is drawn as though the cutting plane were straightened out.
Broken-Out Section
A broken-out section removes only a local area of the part. It is useful when one internal feature needs explanation without creating a complete section view.
Hatching Basics
Cut surfaces are normally identified with section lining. In assemblies, adjacent components should be distinguished by suitable hatch direction or spacing. Standard drawing practice should be followed for the applicable drafting standard.
What Should Not Be Sectioned?
Some conventional drafting practices omit section lining for certain fasteners, shafts, ribs, webs, and other features when the cutting plane passes along their length or when a standard convention applies. Always follow the drafting standard used by the project.
Practical Example
| Problem | Useful section type |
|---|---|
| Internal bore through a symmetric housing | Full or half section |
| Several offset holes | Offset section |
| One internal groove | Broken-out section |
| Symmetric bearing housing | Half section |
Drawing Checklist
- Mark the cutting plane clearly.
- Label the section view consistently.
- Use readable hatch spacing.
- Do not clutter the section with unnecessary hidden lines.
- Dimension the section only where it improves manufacturing clarity.
Related Reading
For the complete drawing-reading workflow, see how to read a mechanical engineering drawing.
Conclusion
A good section view reduces ambiguity. Choose the section type based on the internal feature you need to communicate, apply standard drafting conventions, and keep the view focused on information that manufacturing and inspection actually need.