How does a sectional view reveal internal features that would otherwise be hidden detail?
Sectional views: the cutting plane and section labelling, hatching at 45 degrees, the half section and revolved/removed sections, and the parts conventionally left unsectioned (shafts, fasteners, ribs and webs).
An SQA Higher Graphic Communication answer on sectional drawings, covering the cutting plane and labelling, hatching at 45 degrees, half sections and removed sections, and the parts conventionally left unsectioned such as shafts, bolts and ribs.
Reviewed by: AI editorial process; not yet individually human-reviewed
Have a quick question? Jump to the Q&A page
Jump to a section
What this key area is asking
The SQA wants you to read and produce a sectional view: the cutting plane and its labelling, hatching the cut material at 45 degrees, the half section and removed/revolved sections, and the parts that are conventionally left unsectioned (shafts, fasteners, ribs and webs). A section turns confusing hidden detail into a clear view of what is inside.
The cutting plane and labelling
The plane is marked on a related view by a cutting plane line: a thin chain line, thickened at its ends and at any change of direction, with arrows giving the viewing direction and capital letters naming it. The section view carries the matching title, for example SECTION A-A. This replaces dashed hidden lines with clear solid edges, which is why a section is used when internal detail is complex.
Hatching the cut material
Hatching shows where there is solid material on the cut face; anything not hatched in a section is either a hole/space or a feature left unsectioned by convention.
Types of section
- A full section cuts straight through the whole component on one plane.
- A half section cuts away a quarter of a symmetrical part, giving the inside on one half and the outside on the other in a single view (useful where you want both).
- A removed (or revolved) section shows the cross-sectional shape of a feature (such as a rib or a spoke) drawn beside or revolved onto the view, to reveal its profile without a separate full view.
- A stepped (offset) section changes plane part-way so the line can pass through several features; the cutting plane line is thickened at the change of direction.
Parts left unsectioned by convention
Worked example
Examples in context
Sections are everywhere in engineering drawings: a sectioned pump or valve shows the flow path and seals that hidden detail could never make clear, and a sectioned assembly shows how parts nest together. CAD packages generate sections automatically from a 3D model, applying hatching and honouring the unsectioned conventions.
Try this
Q1. State the angle at which section hatching is normally drawn. [1 mark]
- Cue. 45 degrees.
Q2. State what a half section shows that a full section does not. [1 mark]
- Cue. The inside and the outside of the part in one view (a quarter is cut away).
Q3. State one type of feature left unsectioned by convention. [1 mark]
- Cue. A shaft, a fastener (bolt/nut/screw/rivet/pin/key), or a rib/web along its length.
Exam-style practice questions
Practice questions written in the style of SQA exam questions on this dot point, with worked answer explainers. The year tag is the paper they imitate, not the source.
SQA Higher (style)4 marksDescribe how a sectional view is produced and labelled, and state how the cut material is shown.Show worked answer →
A sectional view is produced by imagining the component cut through along a chosen plane and the near part removed, so you draw what is revealed on the cut face plus everything visible behind it.
The cutting plane is shown on a related view as a thin chain line, thickened (bold) at its ends and at any change of direction, with arrows showing the direction of viewing, and labelled with capital letters, for example A-A. The section itself is then titled to match, for example SECTION A-A.
The solid material that the plane cuts through is shown by hatching: evenly spaced continuous thin lines, normally at 45 degrees. On an assembly, adjacent parts are hatched in opposite directions or at different spacings so the join between parts is clear.
Markers reward: imagine cutting and removing the near part, the cutting plane as a labelled chain line with arrows, the matching section title, and cut material shown by 45 degree hatching.
SQA Higher (style)3 marksState three features that are conventionally left unsectioned (not hatched) when the cutting plane passes along them, and explain why.Show worked answer →
Features conventionally left unsectioned include: shafts and spindles, fasteners (bolts, nuts, screws, rivets, pins and keys), and thin features such as ribs and webs when the plane passes along their length (also balls in bearings).
They are left unsectioned because sectioning them adds no useful information and can mislead. A solid shaft or bolt has no internal detail to reveal, so hatching it just clutters the drawing. Hatching a rib or web along its length would make it look like a solid block of material and hide its true thin shape, so the convention keeps the section clear and honest about the part.
Markers reward: any three valid items (shaft, bolt/nut/screw/rivet/pin/key, rib or web) and the reason that sectioning them adds no information or would be misleading.
Related dot points
- Orthographic projection in third-angle: the six principal views, the front elevation, plan and end elevation, how they line up and project, and the use of the projection symbol and auxiliary views for complex features.
An SQA Higher Graphic Communication answer on orthographic projection, covering third-angle projection, the front elevation, plan and end elevation, how the views project and line up, the third-angle symbol, and auxiliary views for sloping faces.
- British Standards (BS 8888) line types and conventions: continuous thick outlines, thin lines for dimensions and projection, dashed hidden detail, chain centre lines, cutting planes and the conventional representation of repeated features.
An SQA Higher Graphic Communication answer on British Standards line types and conventions, covering continuous thick outlines, thin dimension and projection lines, dashed hidden detail, chain centre and cutting-plane lines, and conventional representations under BS 8888.
- Dimensioning and tolerances: the rules for dimension and projection lines, leaders and arrowheads, dimensioning circles, radii, diameters and angles, datum and chain dimensioning, and stating tolerances (limits, bilateral and unilateral).
An SQA Higher Graphic Communication answer on dimensioning and tolerances, covering dimension and projection lines, arrowheads and leaders, dimensioning diameters, radii and angles, datum versus chain dimensioning, and stating tolerances as limits.
- Assembly and production drawings: the assembly (and exploded) view, item numbers and the parts list, the title block and scale, and the difference between an assembly drawing and a single-part (detail) drawing.
An SQA Higher Graphic Communication answer on assembly and production drawings, covering assembly and exploded views, item numbers and the parts list, the title block, scale, and the difference between assembly and detail drawings.
- CAD assembly and rendering: assembling components with assembly constraints (mate, align, concentric), exploded views and animation, and producing realistic renders with materials, lighting, cameras and an environment.
An SQA Higher Graphic Communication answer on CAD assembly and rendering, covering assembling parts with mate, align and concentric constraints, exploded views and animation, and producing realistic renders with materials, lighting, cameras and an environment.