ISO 8015 & ISO 14405

02 / 07 / 2011

First the bad news. With a couple of minor tweaks, none of which addressed the fundamental objections put forward by the UK and USA, ISO 8015 has now been approved. The UK, USA and Canada all opposed this, but it was passed with a comfortable majority of other nations voting in favour. The invocation principle, which requires all mechanical engineering specifications to be interpreted according to ISO GPS rules unless an alternative standard is specified, is now enforced. The voluntary nature of standardisation, which has always applied in the past, has in this case been removed. You no longer have to opt in to the use of this standard, you now have to opt out, which places a responsibility on anyone involved with mechanical engineering specifications to be aware of the standard and its rules.

With the new version of ISO 8015 now published, much of the content of the previous ISO 8015, dealing with size and the envelope requirement, has been moved to another standard, ISO 14405-1.

ISO 14405-1 is the first standard to really address the whole issue of size properly, and gives a thorough, and long overdue, breakdown of the different ways in which size can be defined. It also provides tools which enable size to be defined in different ways on a specification when necessary. In the absence of any other indication, the previous definitions of size still apply by default.

This is a good standard, which brings clarity to an area of specification which is often poorly understood.

There is also in the pipe-line an ISO 14405-2 standard. This is really concerned with explaining how a specification will inevitably be ambiguous if datums and geometrical tolerances are not used. The UK felt that this content should be produced as a technical report rather than a standard, as it is really just an informative document, but again were over-ruled. However, the content is perfectly valid, and may be of interest to anyone who is not convinced of the necessity of using geometrical tolerancing to specify products.

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