Setting out, marking out, measuring and workshop calculations
Setting out, marking out, measuring and workshop calculations
This domain tests accurate transfer of dimensions from drawing to workpiece and the arithmetic used in cutting lists and costing.
Core rules
- Establish a face side and face edge; all measurements refer to these datums. Mark with a knife and square, not a thick pencil.
- Use the 3-4-5 method or a diagonal check to confirm square. For a rectangle, diagonals must be equal.
- Convert units consistently: 1 m = 1000 mm; 1 m² = 1,000,000 mm²; 1 m³ = 1,000,000,000 mm³.
- Allow for saw kerf, planing allowance and wastage. A cutting list should give finished sizes, material, quantity and grain direction.
- For board area, multiply length by width; for volume, multiply by thickness.
Worked example
A carcass is 600 mm wide, 400 mm high and 300 mm deep, made from 18 mm board. Find the shelf length. Internal width = 600 − 2 × 18 = 564 mm. The shelf fits between the sides, so cut it 564 mm long (or 563 mm for clearance). If the shelf is 280 mm deep, area = 0.564 × 0.280 = 0.158 m². Reasoning: subtracting both thicknesses avoids a shelf that will not fit; converting to metres gives square metres for costing.
Traps
Measuring from a damaged edge; adding rather than subtracting board thickness; forgetting kerf; mixing mm and m; cumulative marking errors; assuming nominal board sizes are exact.