Freehand Sketching and Lettering
This domain tests rapid, proportionally correct sketching without instruments and the standard lettering that makes a drawing legible and professional.
Sketching method
Work from light construction lines to firm outlines. Block in the overall bounding box, divide it into halves and quarters to fix proportions, then add detail. Long lines are drawn from the shoulder with the wrist locked; small curves from the wrist. Circles are sketched by marking the centre, drawing a light square of the diameter, marking the midpoints of the sides, then curving through the four points; ellipses are drawn in a box the size of the major and minor axes. Keep the pencil at a low angle and rotate it slightly to keep the lead even.
Proportion and crating
Judge size by comparison, not by absolute measurement: relate each feature to the overall height or width. The crating method boxes the object in a wire frame so all faces are consistent, which prevents the classic faults of a drawing that looks flat or that shows impossible receding edges.
Lettering standards
Technical lettering follows ISO 3098 single-stroke Gothic: vertical or inclined at 75°, drawn with consistent stroke width and even spacing. Standard heights are 2.5, 3.5, 5, 7, 10 and 14 mm; the ratio of height to stroke width is about 10:1. Lower-case letters are used for notes and upper case for titles, with the same height series. Draw guide lines with a hard pencil and letter between them, spacing letters so the area between them looks equal, not the measured gaps.
Worked example
Sketch a bearing bracket freehand, overall 80 × 60 × 50 mm. Draw a light box 80 wide and 50 high, divide the base to give the 60 mm depth in the receding direction, block the upright as 30 mm of the width, then add the bore as an ellipse in a box on the front face. Reinforce outlines last; keep construction lines faint.
Traps
Pressuring the sketch into a hard outline too early; lettering without guide lines; mixing vertical and inclined lettering on one sheet; letter heights wildly inconsistent; sketching circles as eggs.