BS 8888 is just the new name for BS
about BS 8888
No. BS 8888 is an entirely new standard, and is quite
different in nature and content to BS 308.
2 The only difference between BS 8888
and BS 308 is that now we have to use a comma instead of a full
stop as the decimal marker.
No. Although BS 8888 does specify the comma as the decimal
marker (as this is a requirement of the ISO system), this is
just one of a number of presentational changes introduced by the
More important are the fundamental changes brought in with the system
of Geometrical Product Specification.
3 BS 308 was fine as it was, there was
no need for a new standard.
No. The developments in the ISO system over the last decade
have been driven by technical deficiencies in the traditional
methods of specifying component geometry.
If BS 308 had been retained, the technical changes that
have been introduced in the ISO system would also have been
introduced into BS 308, and the problem of two parallel sets of
standards serving the same purpose would remain.
BS 8888 is just more bureaucracy being
imposed from Brussels.
No. BS 8888 does provide a gateway to the ISO system, but the ISO
system is nothing to do with the EU. ISO is a global federation of national standards
organisations representing over 150 nations.
BSI believes that the adoption of the ISO system has the
potential to bring considerable benefits to industry.
5 To comply with BS 8888, you have to
introduce new procedures for document management, system
security, handling of digital data etc, as well as changes to
engineering drawing practice.
Not necessarily. If your engineering drawings are ‘drawn in accordance
with BS 8888’, this claim only refers to the drawing itself.
If you wish to comply with the requirements of BS 8888
for document management etc, that is a separate issue.
6 If we change to BS 8888, we will have
to go through all our drawing archives to bring them all up to
date with the new standard.
Wrong. An explicit requirement of BS 8888 is that drawings are
interpreted according to the standards that were in force at
their ‘acceptance date’. If a drawing was released on 15th June 1957,
correct to the version of BS 308 current on 15th June
1957, it should be interpreted according to the appropriate
version of BS 308 and it does not have to be up-dated.
The BS 308 Story
In 1927, the British Standards
Institute (BSI) introduced a national standard for engineering drawing
known as BS 308.
This standard was developed and expanded over the next 73 odd
years, until it was finally withdrawn in 2000.
While BSI maintained and developed BS 308 over the years, as a key member of the International Organization
for Standardization (ISO), BSI were playing an important part
in the development of international (ISO) standards for technical
specifications in parallel with this. Many of these international
standards were subsequently incorporated as British Standards. By 2000,
a full set of British standards for engineering drawing included
around 30 ISO standards as well as all three parts of BS 308.
The maintenance of two parallel
sets of standards, which duplicated each other in many ways,
was hard to justify. It led to confusion among users about
which set of standards they should be working to, and about the
differences between them. In the second half of 2000, BS
308 was withdrawn, and BSI took the logical and inevitable step
of adopting ISO standards in full for engineering documentation.
Due to the high level of compatibility between the two sets of standards,
this was a relatively smooth transition, but there have been some
changes to working practices.
About BS 8888
In order to make the transition
from British to ISO standards as painless as possible, BSI produced
a new standard to provide a kind of gateway or interface between
the user and the ISO system.
This new standard performed three
This new standard could have been
published as a new version of BS 308, but the nature and content
of the standard were so different to BS 308 that BSI decided that
it should be given an entirely new name, and BS 8888 came into
Since its introduction, BS 8888
has been revised four times, and the current version is BS 8888:2008
which was published in November 2008.
- firstly, it provided a unifying identity for
all those ISO standards which relate to Technical Product
- secondly, it provided an index
showing which ISO standards dealt with which aspect of technical
product specification (TPS);
- finally, it provided BSI with
a platform for providing additional explanation and commentary where
this was felt to be useful
BSI currently plan to publish revised
versions of this standard approximately every two years, and the
next version is due in October 2010. Altogether BS 8888 refers 'normatively'
to over 130 ISO and EN ISO standards (i.e. these must be complied
with if documents claim to comply with BS 8888), and informatively
to around another 30 (i.e. for information but not mandatory).
BS 8888 - What does it mean in practice?
There are a number of changes and
developments to working practices, many of which would have been
introduced through a new version of BS 308 if it had not been withdrawn. Principle changes can be summarized as follows:-:
BS 8888:2008 - what has changed from BS
A number of 'fundamental principles' which
were previously listed in the front of the document, and which were
largely incomprehensible to readers, have been simplified,
relocated, and in some cases removed altogether.
standards cover more than just engineering drawing, they cover
all aspects of technical product specification, including, for
instance, the use of 3D CAD models to define component geometry.
for drawing borders and title blocks have been formalised and
changed in some areas
The comma is to be used as a decimal marker instead of the full stop.
Size tolerances should be interpreted in accordance with
ISO 8015 (i.e. according to the Principle of
This differs to their interpretation under BS 308, or the
American ASME Y14.5 standard.
use of dimensions, size tolerances, datums, geometrical tolerances,
edge and surface specifications have been formalised and systematised
under the heading of Geometrical Product Specification
(GPS). This approach is the driving philosophy behind BS 8888
and the current generation of ISO standards, and industry will
potentially benefit enormously from its adoption.
The rules governing the use of implied dimensions have been spelt
out. Additional references to ISO standards
have been added to reflect the publication of new ISO standards in
some areas, and to correct omissions in others.
The most important change in the 2008
revision is that there is no longer a requirement to indicate
whether specifications have been toleranced in accordance with the
Principle of Independency or the Principle
of Dependency. BS 8888 now simply follows the ISO
practice of working to the Principle of Independency as defined in
The fact that there is no longer an option to choose to work to the
Principle of Dependency has not led to any technical deficiency in
the system, as the Envelope Requirement may still be invoked when
required. The 'Dependency' option was also in contradiction to the
fundamental purpose of BS8888, which was to act as a gateway into
the ISO system. The benefits of the new approach are:
- BS 8888 is now fully consistent with the ISO system.
- industry is no longer being required to
choose between two different tolerancing principles, when neither is
- there is no longer a risk of two different 'dialects' of BS 8888
- drawings are now to be marked 'TOLERANCING ISO 8015', which is
an internationally recognized means of indicating which standards
govern their interpretation
of Dependency and the Principle of Independency describe the two fundamental ways
in which size tolerances can be interpreted. It is important to know
which principle you are working to from both a design and an inspection point of view.
Under the Principle of Dependency, the envelope
requirement is applied by default to all
features-of-size. Under the Principle of
Independency, it has to be specified.
Both approaches were acceptable under previous revisions of BS 8888, as they were under BS 308.
The Principle of Dependency was the default under BS
308, early revisions of BS 8888, and remains the default
for the American ASME Y14.5 standard. However, the
rules governing its operation have never been fully
defined in any BS or ISO standard, so there were always
potentially some difficulties with it.
The Principle of Independency is defined in ISO 8015,
which also defines the envelope requirement. ISO
8015 is now normatively referenced from BS 8888. A
consequence of this is that all drawings compliant with
BS 8888 must now also state 'TOLERANCING ISO 8015',
which is an internationally recognized indication.
ISO 8015 is due to be replaced by a new standard, ISO
14405, at some point. This is likely to happen in
2010. Watch this space - we will post further
details about ISO 14405 when they become available.
BS 8888 formats:
BS 8888:2008 can be purchased in paper
format, either on its own or in 'kits' (where
it is supplied with sub-sets of the referenced ISO standards), or as
The CD ROM includes all the ISO standards that are referenced from
within BS 8888 in PDF format. Each reference within BS 8888 is
hyper-linked to the appropriate ISO standard to ease navigation
through the system.
BSI have also been working on the development of an 'on-line'
version of the standard.
When available, this will work in a similar way to the CD ROM
version, with links to all the referenced ISO standards, but also
with additional guidance and explanation. This web-based version has
been delayed, and is now likely to appear later in
All engineering drawing and geometrical tolerancing training offered
by Iain Macleod Associates takes full account of the changes to
BS 8888 (and is now fully updated to take account of changes in
BS 8888:2008), and conforms with current ISO standards.