4 min read
Mathew Wahome
Drawing Instruments and Lines
Introduction
In the Junior School CBC (KICD), Pre-Technical Studies introduces graphic communication. Technical drawings must be accurate, clear and follow standard conventions so that anyone can understand and build from them.
Drawing instruments
| Instrument | Use |
|---|---|
| Pencils (H, HB, 2H) | Drawing lines of different darkness |
| Ruler | Measuring and drawing straight lines |
| Set squares (45 and 30/60 degrees) | Drawing angles and perpendicular lines |
| Protractor | Measuring angles |
| Compass | Drawing circles and arcs |
| T-square or drawing board | Drawing horizontal lines |
| Eraser | Removing mistakes |
Types of lines
- Outline (thick continuous): visible edges.
- Construction (thin continuous): light guide lines.
- Hidden detail (short dashes): edges not visible.
- Centre line (long and short dashes): centres of circles and symmetry.
- Dimension lines (thin with arrowheads): show measurements.
Layout of a drawing sheet
Border, title block (name, date, scale, title), then the drawing. Keep drawings neat and use capital letters for text.
Basic constructions
- Bisecting a line: with a compass at each end, using more than half the length, draw arcs above and below; join the intersections.
- Perpendicular at a point: use a set square or compass arcs.
- Angle of 60 degrees: draw an arc from the line's end and mark the same radius from the arc.
Worked example
To draw a 10 cm line bisected: draw AB = 10 cm. Set the compass to 6 cm. Draw arcs from A and B above and below. Join the two crossing points; the crossing on AB is the midpoint at 5 cm.
Care of instruments
Keep pencils sharp, wipe the board, store instruments in a case.
Try it
- Draw a 12 cm line and bisect it.
- Draw a rectangle 8 cm by 5 cm with dimension lines.
- Name the line types used to draw a hole inside a block.