Graphics and Communication
Graphics and Communication tests your ability to read and produce technical drawings that a craftsperson could build from. It covers projection, line conventions, dimensioning, scale and freehand sketching.
Core rules
- Visible outlines are continuous thick lines; dimension, projection and hatching lines are continuous thin; hidden details are dashed; centre lines are chain.
- Dimensions are given in millimetres on construction drawings. Put numerals above a continuous dimension line, keep lines clear of the drawing, and do not repeat a dimension in two views.
- In first-angle projection the front elevation is drawn first, the plan is projected below it and a side view is placed on the opposite side. Project every feature, including hidden edges.
- A scale of 1:10 means the drawing is one-tenth full size. A bar scale is safer than a stated ratio if a drawing is photocopied.
Worked example
A rectangular block is 60 mm long, 40 mm deep and 20 mm high. At 1:1, draw a front elevation 60 mm × 20 mm and a plan 60 mm × 40 mm below it. Project the vertical edges from the elevation down to the plan. If a 10 mm hole runs through the depth, show it as a hidden circle in the plan and as dashed lines in the elevation. Dimension overall length and height once, not each projection line.
Traps
Mixing first- and third-angle projection is the commonest error: in third angle the plan sits above the elevation. Other mark-losers are dimensioning a hidden edge, using thick lines for dimensions, and forgetting that a scale ratio applies to every dimension.