Sectional Views and Conventions
This domain tests whether you can cut a component on a defined plane and present the interior clearly, using the standard conventions rather than inventing your own.
The cutting plane and hatching
Mark the cutting plane on an adjoining view with a heavy chain line, thickened and arrowed at the ends to show the direction of sight, labelled A–A. The section view carries the title SECTION A–A. Exposed cut material is hatched with thin continuous lines at 45° to the principal outlines, evenly spaced about 2–4 mm apart. Hatch the same part in the same direction throughout; hatch adjacent separate parts in opposite directions or at different spacings so the joint stays visible.
Types of section
A full section cuts right through. A half section removes one quarter and is used for symmetrical parts, showing half in section and half in outside view, separated by a centre line. An offset section steps the cutting plane to pass through features not in one plane. A revolved section is drawn on the view itself, and a removed section is drawn nearby and labelled. A broken-out section exposes only a small local feature, bounded by a freehand break line.
Conventions you must know
Ribs, webs, spokes, gear teeth, shafts, bolts, nuts, keys, pins and similar solid items are not hatched when the cutting plane passes through them lengthwise; they are treated as solid to avoid giving a false impression of mass. Hidden detail is normally omitted from a section unless it is essential. Standard material hatching applies for cast iron, steel, aluminium, brass, concrete and plastics.
Worked example
A cast bracket has a vertical plate and a triangular rib. Cut A–A runs through the rib's length. In the section, the plate is hatched but the rib is outlined solid with no hatching, because a lengthwise cut through a thin stiffening web is not hatched. Hatching it would make the bracket look far heavier than it is.
Traps
Hatching the rib; arrows on the cutting plane pointing the wrong way so the section is a mirror image; hatching at odd angles into corners; drawing section lines thick and black instead of thin; forgetting the label.