Board Practice and Scale Drawing – JSS1 Basic Technology Lesson Note (Second Term)

Board practice is the skill of using drawing instruments on a drawing board to draw vertical, horizontal and inclined lines neatly and accurately.

Behavioural objectives

By the end of the lesson, students should be able to:

1. define board practice;
2. list the instruments used in board practice and state the use of each;
3. set up a drawing board in the correct steps;
4. draw horizontal, vertical and angled lines;
5. state the information in a title block and where it is placed;
6. define scale and calculate lengths for a scale drawing.

What is board practice?

Board practice is the act of learning how to use drawing instruments on a drawing board to draw vertical, horizontal and inclined lines.

• Aim: to produce clean, accurate and neat drawings.
• Requirement: the appropriate drawing instruments must be used for each job.
• Setting: the drawing paper is fixed on a drawing board before work begins.

What are the instruments used in board practice?

There are eight main instruments used in board practice, listed in the table below with their uses.

How do you set up the drawing board?

The board is set up in six steps, so that the paper is fixed straight and does not move.

1. Place the drawing board conveniently on the table with the square edge to the left-hand side.
2. Place the drawing paper on the board, leaving equal space all around.
3. Place the tee-square on the paper, and gently slide the tee-square to the top edge of the paper.
4. Set the top edge of the paper parallel to the edge of the tee-square, with the stock of the tee-square firmly against the edge of the drawing board on the left-hand side.
5. Gently slide the tee-square down without moving the paper.
6. Cut pieces of adhesive tape to hold the paper in position, and place them over the four corners of the paper.

How are lines drawn on the board?

Lines are drawn with the tee-square and set-square, which are kept firm against the board edge or each other.

Horizontal lines

• Instrument: the tee-square, with its stock held firmly against the left edge of the board.
• Direction: draw the line from left to right.
• Pencil: rotate the pencil slowly as the line is drawn.
• Result: rotating the pencil gives a line of uniform thickness.

Vertical lines

• Instrument: the set-square, sitting on the tee-square.
• Method: slide the set-square along the tee-square to the right position.
• Result: the upright edge of the set-square draws a line at a right angle to the tee-square.

Angled lines

• Instrument: the set-square, turned in different directions on the tee-square.
• 45-degree set-square: draws lines at 45° and 90°.
• 30-60 degree set-square: draws lines at 30°, 60° and 90°.
• Two set-squares together: give other angles, such as 15° and 75°.
• Other angles: mark them with a protractor.

What is a title block and where is it positioned?

A title block is a small box that gives the main information about a drawing, placed at the bottom right-hand corner.

It consists of the following information:

1. Title of drawing
2. Name of object
3. School
4. Scale
5. Date

Lettering in the title block

• Style: the title block is lettered free-hand in single-stroke capitals.
• Vertical lettering: the letters stand upright.
• Inclined lettering: the letters lean to one side.
• Rule: only one method of lettering should be used on a drawing.

What is scale drawing?

Scale drawing is a way of drawing an object larger or smaller than its real size while keeping its shape and proportions correct.

• Scale: the ratio of the length on the drawing to the real length of the object.
• Why it is used: a building cannot fit on paper at full size, and a small screw is too tiny to show detail.
• Where it is shown: the scale is written in the title block, for example 1:10.

What are the types of scale?

There are three types of scale: full size, reduction and enlargement.

• Reading a scale: in 1:10, 1 unit on the drawing stands for 10 units on the object.
• Use of reduction: for large objects such as rooms, houses and tables.
• Use of enlargement: for very small objects such as screws and watch parts.

How do you calculate lengths in a scale drawing?

For a reduction scale, divide the real length by the scale number to get the drawing length.

1. Write the real length in millimetres.
2. Divide by the scale number (for 1:20, divide by 20).
3. Draw the answer in millimetres on the paper.

Worked examples

• Example 1: a table is 2 m long. At 1:20, 2 m = 2000 mm, and 2000 ÷ 20 = 100 mm on the drawing.
• Example 2: a wall is 5 m long. At 1:50, 5000 ÷ 50 = 100 mm on the drawing.
• Example 3: a line on a drawing is 60 mm at 1:5. The real length is 60 × 5 = 300 mm.
• Example 4: a screw is 4 mm long. At 5:1, the drawing length is 4 × 5 = 20 mm.

Evaluation

1. Define board practice.
2. Mention the steps involved in setting up the board.
3. How can horizontal and vertical lines be drawn?
4. List the information required in the title block.
5. A room is 4 m long. What length will it be on a drawing at a scale of 1:50?

Assignment

Answer these in your notebook:

1. List the eight instruments used in board practice.
2. State how the set-square is used to draw vertical and angled lines.
3. State the three types of scale and give one example of each.