Technical Drawing, Sketching and Communication
Drawing conventions
Know the difference between sketching (freehand, for ideas) and formal drawing (accurate, to scale). Understand orthographic projection: front, plan and side views arranged in first-angle or third-angle projection, with hidden detail as dashed lines and centrelines as chain lines. Know isometric and oblique pictorial drawings, and that isometric axes are at 30 degrees to the horizontal while true lengths are drawn along them.
Dimensioning and annotation
Dimensions show true sizes, not scaled sizes. Include dimension lines, extension lines, arrowheads and units. Add notes for material, finish, quantities and tolerances. A frequent trap is dimensioning a drawing so that a dimension is repeated or missing, leaving the maker to calculate it. Give each feature once.
Other communication methods
Candidates should recognise flow charts, exploded views, assembly drawings, cutting lists, parts lists, storyboards and CAD models. Know why a cutting list accompanies a working drawing and why an exploded view helps assembly.
Worked example: a simple bracket
To draw a right-angled steel bracket, sketch it isometrically to explain the idea, then produce front and plan views in orthographic projection with hidden lines for the holes, and dimension the hole centres, diameters, plate thickness and overall size. Add a note: 'mild steel, 3 mm, deburr all edges'. The drawing is now a working drawing.
Rule of thumb
A drawing is only complete when a competent stranger could make the part without asking you a question.