Department
of
Technological
Education
Graphic Communication
British Standards
Knowledge & Understanding
British Standards - Drawing Conventions
Line Types
Dimensioning
• Why?
• We have a greater understanding of why we are
doing things in a certain way.
• We have an broader understanding of the
implications it has on industry.
What does British standards
mean to you?
• The British Standards Institution (BSI) is
the UK's national standards body.
• It brings together representatives from a
range of organisations to develop formal
Standards for the benefit of UK business
and consumers.
British Standards
• Standards make our lives easier, safer and
healthier. Without them, everyday actions we
take for granted would be unpredictable.
• Standards help to make many of the products
we use safer and more reliable.
• Once you are familiar with the idea of products
meeting Standards, it will help you to understand
how Standards are met in order to keep us safe
and sound.
British Standards
• In Short they are set methods/procedures
that allow us to consistently reproduce
quality products.
• With regards to Drawings BS allows
standardisation ie. It creates a common
language between professional people.
British Standards –Drawing
• BS EN ISO 128-20:2001 - Technical drawings. General
principles of presentation. Basic conventions for lines.
• BS EN ISO 128-21:2001 - Technical drawings. General
principles of presentation. Preparation of lines by CAD systems.
• BS EN ISO 5456-2:1999 - Technical drawings. Projection
methods. Orthographic representations.
• BS 308-2.3:1995 -Technical drawings. Dimensioning and
tolerancing.
• BS ISO 128-40:2001 -Technical drawings. General
principles of presentation. Basic conventions for cuts and sections.
• Visible Outlines
and Edges.
A continuous thick line.
• Construction,
projection and
dimension
projection.
A continuous thin line.
These are the two basic line thicknesses recommended
in the BS. However you will see there are variations in
Their use.
• Hidden outlines and
edges.
A broken thin line. Dashed
lines should start on a line
& finish on a line. Dashes
and spaces should be of
even length and spacing.
• Centre Lines.
Thin line.
Long dash – short dash. Centre
lines should extend slightly
passed the feature it applies to.
They should not stop at another
line.
Where centres points are
defined – long dashes should
cross.
• Section lines
(cutting planes)
• Fold lines
Like the centre line but
ends and change of
direction are thick
Thin line.
Chain of long dash and two
short dashes.
Question?
Solution!
Question?
Solution!
Section Line
Fold Line
Centre line
• When applying measurements there are
some simple rules to follow!
1
Projection lines should be
thin and disconnected from
the part.
12
2
Arrow heads should be narrow
Filled
17
14
3
Sizes should be written
Clearly ABOVE the line
• Two methods we should know for now!
12
12
17
14
29
43
Linear Dimensioning
Parallel Dimensioning
• For A radius…
The dimension line should pass
through the centre point of the
arc.
The dimension line should
have one arrowhead that
touches the arc.
R10
The symbol R is placed in front
of the dimension.
• For a Diameter…
The dimension line should pass
through the centre point of the
arc.
The dimension line should
have two arrowheads that
Touch the arc.
The symbol Ǿ is placed in front
of the dimension.
Ǿ 10
• For Angles…
Curved double headed arrow
between lines.
The angle is written outside the
Arrow.
Alternatively Arrows can be
Outside with the angle written
Lines.
30°
30°
•
•
•
•
Angle used is 45°
Spacing equal 4mm
For Exploded views direction of hatching
is the same.
For assembled views
1. Part 1 in one direction
2. Part 2 in the opposite direction with same
spacing.
3. Part 3 spacing reduced to half.
Assembled
Exploded
We do not Hatch…
1. Nuts, Bolts, washers.
2. Keys, Webs, Shaft.
3. Spindles, Gears, Pins.
– Note – Shafts are only sectioned if cut
through the cross sectional area.
Go for it!
• BSI-Education.org/BritishStandards