Sections and auxiliary views

A section view imagines the part cut along a cutting plane (labelled A–A) and shows the cut surface. Internal features become visible edges instead of hidden lines, making drawings much clearer.

• Full section: cut right through.

• Half section: a quarter removed — shows inside and outside of symmetrical parts.

• Offset section: the cutting plane steps to pass through several features.

• Broken-out section: a small local cut-away.

• Revolved / removed section: the cross-section of a bar or arm shown rotated in place or nearby.

Cut surfaces are hatched with thin lines, typically at 45°. Adjacent parts in an assembly get different angles or spacing. Keep hatching consistent for one part across all views. Material-specific patterns exist, but many standards now use general hatching and state the material in the title block.

By convention, some items are not hatched even when the cutting plane passes along them: shafts, bolts, nuts, pins, keys, ribs and webs cut lengthwise, and similar solid features — hatching them would mislead.

An inclined face appears foreshortened in principal views. An auxiliary view looks perpendicular to it, showing true shape and size so features on it can be dimensioned. Often only the inclined face is drawn in the auxiliary view.