Free Hand Sketching – JSS2 Basic Technology Lesson Note (Second Term)

Freehand sketching is the quick drawing of the shape of an object with a pen or pencil, without using drawing instruments.

Behavioural objectives

1. Define freehand sketching.
2. Sketch a straight line, a curve and a circle.
3. Describe how to sketch a square and an irregular edge.
4. Define scale drawing and state the materials and instruments used for it.
5. Name the types of scale drawing and give examples of each.

What is freehand sketching?

Freehand sketching is one of the quickest ways of communicating the shape of an object to others, using a pen or pencil.

• Speed: a sketch shows an idea in a few minutes.
• Less writing: a good sketch reduces the writing needed to describe the object in the designer’s mind.
• Imaginary objects: architects often work with objects that do not yet exist. They cannot photograph them, so they sketch them.
• Skill: the ability to sketch freehand is a valuable asset gained through practice.

Tips for good freehand sketching

• Light lines: draw faintly first so that mistakes are easy to correct.
• Relaxed hand: hold the pencil loosely and move the whole hand, not only the fingers.
• Eyes on the end point: look at where the line will finish.
• Practice: sketch often to improve control.

How do you sketch a straight line?

A straight line is the shortest distance between two points, and you sketch it by drawing towards a fixed end point.

1. Put a dash or dot far enough to the right-hand side of the paper.
2. Start to draw a line from the left-hand side to join the dash or dot.
3. Keep your eyes fixed on the dash or dot as you draw.

How do you sketch a curve and a circle?

A curve is drawn by joining plotted points smoothly, and a circle is drawn by joining the tips of equal lines with small curves.

Curve

1. Plot some points not too far from each other, at different levels.
2. With the points in position, draw a smooth curve to join them.

Circle

1. Draw several lines equal in length to the diameter of the circle, in different directions.
2. Draw each line as faintly as possible, with all the lines crossing one another at one point.
3. Join the tips of the lines with little curves.

How do you sketch a square and an irregular edge?

A square or an irregular edge can be sketched in an isometric view or an oblique view.

• Isometric view: the sloping lines are drawn at 30° to the horizontal on both sides.
• Oblique view: the sloping lines are drawn at 45° to the horizontal on one side.
• Irregular edge: plot points along the edge, then join them with light lines to follow its shape.

What is scale drawing?

Scale drawing is the accurate representation of objects in a determined proportion, so the object appears reduced or enlarged.

• Reducing scales: make the drawing smaller than the object.
• Enlarging scales: make the drawing bigger than the object.

How is freehand sketching different from scale drawing?

Freehand sketching is quick and done without instruments. Scale drawing is accurate and done with instruments to a stated proportion.

What materials and instruments are used for scale drawing?

The main instruments for scale drawing are the metric rule and the scale rule, used with drawing paper and a pencil.

Metric rule

• Shape: it has two flat straight edges and is usually 30 cm long.
• Main divisions: each main division is 1 cm, and 1 cm = 10 mm.
• Small divisions: each centimetre is divided into 10 units of 1 mm.
• Use: always start your measurement from 0.

Scale rule

• Shape: it is triangular and has three straight edges.
• Graduation: each edge is graduated, and each scale designation is marked on the rule.

Other materials

• Drawing paper: the surface on which the drawing is made.
• Pencil and eraser: for drawing lines and correcting mistakes.

Why do we draw to scale?

We draw to scale because some objects are too big to fit on drawing paper and some are too small for their parts to be seen.

• Large objects: a house or a road is drawn smaller than its real size.
• Small objects: a watch part or a screw is drawn larger than its real size.
• Ratio: a scale is usually given as a ratio and is stated in the title block.

What are the types of scale drawing?

There are three types of scale drawing: full scale, reduced scale and enlarged scale.

Full scale drawing

• Meaning: the object is drawn to the same size as its actual size.
• Example: 1:1.

Reduced scale drawing

• Meaning: the actual size of the object is reduced in proportion on the drawing.
• When used: when the object is too big for the paper.
• Examples: 1:2, 1:5, 1:10, 1:50 and 1:100.
• Worked example: a cupboard 1800 mm long drawn as 18 mm has a reduced scale of 1:100.

Enlarged scale drawing

• Meaning: the actual size of the object is enlarged in proportion on the drawing.
• When used: when the object is too small to be seen clearly.
• Examples: 2:1, 10:1 and 100:1.
• Reading the ratio: in a scale such as 100:1, the first figure is the drawing size and the second is the actual size.

Summary table of scales

Evaluation

1. Define freehand sketching.
2. Describe how to sketch a straight line.
3. Describe how to sketch a circle.
4. Define scale drawing and name two instruments used for it.
5. Mention the three types of scale drawing and give one example ratio of each.

Assignment

Sketch a straight line, a curve and a circle by freehand using the steps in this lesson, then write one example ratio each for a full scale, a reduced scale and an enlarged scale.