Engineering Drawing and Technical Graphics
This domain tests drawing literacy rather than freehand skill: projection layout, line convention, dimensioning rules, sectioning and the tolerance notation that turns a shape into a manufacturable instruction. Questions usually ask you to identify correct view placement, a missing dimension, or the meaning of a symbol.
Views and layout
- Third-angle projection: the top view sits above the front view and the left-side view sits to the left; the truncated-cone symbol identifies the system.
- First-angle projection: the top view sits below the front view and the left-side view is drawn on the right.
- Six principal views exist; use the minimum number that describes the shape fully without hidden detail.
Line convention
Continuous thick = visible edge; dashed = hidden edge; chain thin = centre line or pitch circle; continuous thin = dimension line, leader, hatching. Two crossing centre lines mark a hole centre.
Dimensioning
State the true size, never the scaled size. No dimension appears twice and none is placed on a hidden line; dimensions run to visible outlines and the chain is not closed. Limit notation such as Ø40 H7/g6 means a hole-basis H7 hole running with a g6 shaft.
Sections
Show the cutting-plane line with arrows for viewing direction; hatch at 45°, hatch adjacent parts in opposite directions, and do not hatch solid shafts or ribs cut longitudinally.
Worked example. A 1:5 drawing measures 36 mm between two centres on paper. True distance = 36 × 5 = 180 mm. A dimension written Ø25 ±0.05 gives upper limit 25.05 mm, lower limit 24.95 mm, tolerance 0.10 mm.
Traps. Placing the top view below the front view in third-angle; dimensioning to a hidden line; writing the scale as 5:1; hatching a solid shaft cut along its axis; omitting the projection symbol.