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HOMEWORK NOTES
TOPIC 1: British Standards: including third angle projection,
dimensioning, line types and use of simple scale
Drawing Symbols
This symbol is the third angle projection symbol. It is found on all orthographic drawings , drawn using British Standards.
Orthographic Drawing
An orthographic drawing drawn using British Standards is laid out like this. The Plan is always aligned above the Elevation. The End Elevations are always aligned to the right or left of the elevation as shown.
Dimensions
Dimensions on a British Standard drawing look like this.
Notice how dimensions are always in millimetres so there is no need to add 'mm' after writing the number. Numbers are always written above the dimension line.
Notice that radius dimensions are preceded by capital R and diameter dimensions by the diameter symbol
Linear
dimension
(vertical)
Radius
dimension
Diameter
dimension
Angular
dimension
Linear
dimension
(horizontal)
Line Types
You will also notice that there are several different lines used in this drawing. The complete list of line- types used in British Standard drawing are shown below.
Continuous thin. Used for construction lines, leader lines, dimension lines, hatch lines on sectional views (see below)
Continuous thick Used for outlines
Dashed thin Used for Hidden detail
Chain thin a) Used for centerlines and lines of symmetry.
b) When thick ends are added this line is also used as a cutting plane in a sectional view
Double dashed chain thin Used for foldlines on development drawings
Sectional Views
When an object in an orthographic view is cut it creates a section or sectional view. It is used to give clear detail about the assembly or internal components in a product.
Look at the example of a shopping trolley wheel and bracket below. Notice the position of the cutting plane ( line X-X ) and how the sectional end elevation is different from a normal end elevation, because it shows angled hatch lines on most surfaces that have been cut.
A A
Cutting
Plane
Line X-X
Hatch Lines
Sectional End Elevation X-X^ Elevation
Look at the different views in Drawing X at the top. How would the views change if they became sectional views?
Write in the number that correctly shows the sectional plan view A-A
and the sectional front elevation view B-B
4 __________________
HOMEWORK 1 QUESTIONS
Question 1 (mark out of 8)
Question 2 (mark out of 4)
Name the line types shown at 1, 2 and 3 and 4
1__________________
2__________________
3__________________
4 __________________
Name the symbol shown at Y________________
This symbol is always used on a particular type of drawing name it
Measure and add the correct dimensions to these drawings using British Standards. Use the leader lines provided for you
Question 3 (mark out of 6)
There are 3 mistakes in the British Standard drawing below, unrelated to the values in millimetres.
a) Write down what these mistakes are.
1._____________________________________________________________________________
2. ._____________________________________________________________________________
3. ._____________________________________________________________________________
b) Make changes to the drawing so it shows now the correct dimensioning techniques.
80
15
10
75
