SQA Higher Graphic Communication Area 2D Graphic Communication: a complete overview of orthographic projection, British Standards conventions, dimensioning, sections, assemblies and building drawings
A deep-dive SQA Higher Graphic Communication guide to the 2D graphic communication area. Covers third-angle orthographic projection, British Standards line types and conventions, dimensioning and tolerances, sectional drawings, assembly and production drawings, and building drawings with standard symbols.
Reviewed by: AI editorial process; not yet individually human-reviewed
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What 2D graphic communication actually demands
The 2D graphic communication area is the technical, production side of Higher Graphic Communication: making and reading the drawings that let a part or building be manufactured accurately. The examiners reward correct projection, the right British Standard line for every feature, precise dimensioning and tolerancing, clear sections, and a well-organised assembly. At Higher the components carry complex features (sloping faces, internal detail, multiple parts), so the conventions you learned at National 5 are applied with more care.
This guide walks through the key areas, then sets out the patterns the SQA repeats. Each key area has a matching dot-point page with practice questions; this overview ties them together.
Orthographic projection
The area is built on third-angle orthographic projection. The front elevation is the master view; the plan sits below it and the end elevation to the side. Widths project vertically, heights project horizontally, and depth is transferred between plan and end elevation with a 45 degree mitre line. The projection symbol states the convention, and an auxiliary view is projected at right angles to a sloping face to show its true shape.
British Standards line types
Every line carries a fixed meaning under BS 8888: continuous thick outlines, continuous thin dimension and projection lines, thin dashed hidden detail, thin chain centre lines, and a chain line thickened at the ends with arrows for the cutting plane. Conventions give an agreed shorthand for repeated features (threads, knurling, springs, repeated holes), saving time while staying universally understood.
Dimensioning and tolerances
Sizes are added with thin projection and dimension lines, neat arrowheads, the diameter symbol O for circles and R for radii, and angles in degrees. Datum dimensioning measures from one reference (preventing tolerance build-up); chain dimensioning measures feature to feature. A tolerance is the permitted variation, given as upper and lower limits (bilateral both sides of nominal, unilateral one side), needed because no process is perfectly exact and because tight tolerances cost more.
Sectional drawings
A section cuts through the component and removes the near part, turning hidden detail into clear outlines. The cutting plane is labelled (A-A), cut material is hatched at 45 degrees, and half and removed sections give inside-and-outside or cross-sectional profiles. Shafts, fasteners, ribs and webs along their length are left unsectioned by convention.
Assembly and production drawings
A detail drawing makes one part; an assembly drawing shows all parts together with item numbers (balloons) and a parts list (name, quantity, material). An exploded view pulls the parts apart along their assembly axes for build and service instructions. The title block records the drawing's identity (title, number, scale, projection, material, date, revision); dimensions are always true size whatever the scale.
Building drawings and symbols
Architectural drawings apply the same orthographic system: the site plan (small scale, locating the building), the floor plan (a horizontal section showing layout), elevations (external faces) and sections (construction). Recognised scales (1:500, 1:100, 1:50) keep the building in true proportion, and British Standard symbols represent doors (with a swing arc), windows, sanitary fittings and services.
How 2D graphic communication is examined
A typical SQA profile for this area:
- Reading drawings. Interpreting third-angle views, sections, dimensions and symbols on an unfamiliar component or building.
- Producing or completing drawings. Adding a missing view, a section, dimensions or an auxiliary view to standard.
- Explanation. Justifying datum versus chain dimensioning, the choice of section, the use of conventions, and the difference between assembly and detail drawings.
Check your knowledge
A mix of recall and explanation questions covering 2D graphic communication. Attempt them, then check against the solutions.
- In third-angle projection, where is the plan placed relative to the front elevation? (1 mark)
- State the line type used for a centre line. (1 mark)
- State the symbol written before a diameter dimension. (1 mark)
- State the angle at which section hatching is normally drawn. (1 mark)
- State what is listed against each item number in a parts list. (1 mark)
- State the type of building drawing that locates a building on its plot. (1 mark)