Sectional Views, Cutting Planes and Hatching

≈ 40 min

Sectional Views, Cutting Planes and Hatching

When a part has enough internal structure that hidden detail becomes unreadable, you section it: imagine cutting through, removing the near half, and drawing what is exposed.

The cutting plane is shown on another view as a chain line, thickened at its ends, with arrows showing the direction of sight and letters naming it (A–A). The sectional view is then labelled Section A–A.

Hatching marks material that the cut passed through — thin lines at 45°, evenly spaced. Space that the cut passed through but where there was no material — the inside of a hole — is not hatched, because nothing was cut there.

Hidden detail is normally omitted in a sectional view. The whole purpose of sectioning was to turn hidden edges into visible ones, so leaving dashes in defeats it.

Worked example. Cutting through a block with a hole: the hole becomes a gap in the hatching. A learner who hatches straight across the hole has drawn a solid block and deleted the feature the section was made to reveal.

Core checkpoint: Hatch only what the knife passed through. Where there was a hole, there was nothing to cut.

In a sectional view, which areas are hatched?

Only the areas where the cutting plane passed through solid material.

The whole outline of the sectioned view.

Only the areas containing holes.

Every area behind the cutting plane.

Why should hidden-detail dashes normally be omitted from a sectional view?

Sectioning exists to turn hidden edges into visible ones, so retaining dashes defeats its purpose and re-clutters the view.

Because dashes cannot be drawn over hatching.

Because sections are always drawn at a smaller scale.

They should always be retained, not omitted.

In a sectioned assembly, why are adjacent components hatched at different angles or spacings?

So the boundary between separate components is visible — uniform hatching would make the assembly read as one solid piece.

To indicate that the components are made of different materials.

To show which component is heavier.

It is purely a decorative variation.

How is the position of a section indicated on the other view?

By a chain line thickened at its ends, with arrows showing the direction of sight and identifying letters such as A–A.

By a continuous thick line across the view.

By hatching that view as well.

By a note in the title block only.