The International Standards Organisation has published a new version of ISO 898-1, the fundamental mechanical property standard for carbon and alloy steel bolts, well before the normal five-year review schedule. Fastener consultant, Dr John Newnham considers the reasons for this early revision and its implications for the fastener industry.

The fundamental mechanical property standard for carbon and alloy steel bolts, which identifies the strength grades, permissible material types, and required tests and methods, is ISO 898-1. This standard is not only used to define the properties of ISO standard bolts, screws and studs, but is called up in numerous proprietary drawings for non-standard fasteners. ISO published the new 2013 version of this standard in January, well before the normal ISO five-year review schedule.

The 2009 issue of the same standard was quite controversial, and several aspects drew comments from various national standards bodies. As a result, ISO Technical Committee 2 sub-committee 11 drafted two amendments to the document to take account of the technical and editorial problems. However the changes were so extensive that rather than issue the amendments separately, ISO 898-1 was re-published with all of the amendments included. The ‘Foreword’ to the standard states that this is a minor revision, but there are some technical changes that could cause some products manufactured before the changes to be out of specification now.

There are numerous editorial revisions for clarification, and the usual updates where necessary, relating to reference standards. The newly agreed ISO practice of not dating the reference standards is continued, to ensure that the latest issue of any quoted standard applies immediately.

There are no changes to the material types or strength grades in this edition, so Table 2 is unchanged. But there are increases to the maximum and minimum Brinell hardness values for property classes 8.8 and above, as given in ‘Table 3. Mechanical and Physical Properties’. Since the new ISO philosophy relating to updated standards is that the latest issue applies, these changes could result in parts being in stock that do not comply with the new requirements.

Other technical changes relate to the definitions and assessment of carburization and decarburization. There is a newly defined surface condition, ferritic decarburization, and there is a clarification of non-carburization which applies to strength grades 8.8 and above. There is also some revision to the way that these conditions must be assessed by microhardness tests and metallography so these need to be reviewed by test laboratories.

ISO classifies this edition as a minor revision, but the technical changes are significant, and both manufacturers and distributors need to be aware of them. The new issue of EN ISO 898-1 is available from national standards organisations.