Graphical Communication and Technical Drawing
Graphical Communication and Technical Drawing
This domain tests the drawing conventions that let a design be manufactured or built without verbal explanation. In Design and Communication Graphics it covers sheet layout, linework, lettering, scale, orthographic projection, sections, dimensions and freehand communication.
Core rules
- Irish technical drawing uses first-angle projection: the view from the front is placed above the plan, and the view from the left is placed on the right.
- Line hierarchy carries meaning: continuous thick for visible outlines, short dashes for hidden edges, chain lines for centre lines, thin continuous for dimension and projection lines.
- Dimensions are given in millimetres by default; the unit is stated once in the title block, not repeated on every dimension.
- Dimension from visible edges or centrelines, not from hidden detail, and never duplicate a size in two views.
- Every drawing needs a title block, scale, projection symbol where required, and a layout that leaves space for dimensions.
Worked example
A bracket is 80 mm long, 50 mm high and 20 mm deep, with a 20 mm square notch centred on the top edge, 10 mm deep. Choose the front elevation as the face showing the notch; project the plan below it and the end view to its right. The notch appears as a true shape in the front view, projects as two hidden vertical lines in the plan, and appears as a hidden rectangle in the end view. Dimension overall length, height and depth, then the notch width and depth from the top edge. Use the overall dimensions as datum references so the notch is not dimensioned from two different edges.
Traps that cost marks
Second-angle layout, mixing hidden and centre lines, dimensioning to hidden lines, missing overall dimensions, inconsistent line weights, and forgetting the scale or title block.