NATIONAL FOREWORD

This Indian Standard (Part 3) (Fifth Revision) which is identical with ISO 4034 : 2012 ‘Hexagon regular nuts (style 1) — Product grade C’ issued by the International Organization for Standardization (ISO) was adopted by the Bureau of Indian Standards on recommendation of the General Engineering and Fasteners Standards Sectional Committee and approval of the Production and General Engineering Division Council.

IS 1363 was originally published in 1960 and first revised in 1967. Subsequent to the publication of 1967 edition, many changes had been agreed upon at international level which have been reflected in IS 1367 series of standards covering ‘Technical supply conditions for threaded steel fasteners’. Accordingly, the second revision was published in 1984 splitting the standard into 3 parts covering hexagon head bolts, hexagon head screws and hexagon nuts. The third revision of this standard was published in 1992 by adoption of ISO 4034 : 1988. The fourth revision was prepared by adoption of ISO 4034 : 1999. The remaining parts of the standard, that is, Part 1 and Part 2 have also been revised by adopting the corresponding latest editions of ISO Standards published in 1999.

In 1967 version of this standard, the widths across flat dimensions for M10 and M12 size fasteners were specified as 17 mm and 19 mm respectively. However, in the 1984 version these width across flat dimensions were brought in line with ISO 4034 : 1979 and specified as 16 mm and 18 mm respectivelyfor M10 and M12 size fasteners. Recognizing the difficulty of immediate changeover to new width across flat dimensions, the Committee decided to permit width across flat dimensions as per 1967 version, that is, 17 mm and 19 mm for M10 and M12 size fasteners till 31 December 1994. Now it is expected that the entire fastener industry would have switched over to new width across flat dimensions and from 1 January 1995, no old width across flat dimensions shall be permitted. This fifth revision of this standard has been undertaken to align it with the latest version of ISO 4034 published in 2012.

The text of ISO standard has been approved as suitable for publication as an Indian Standard without deviations. Certain terminologies and conventions are, however, not identical to those used in Indian Standards. Attention is particularly drawn to the following:

a) Wherever the words ‘International Standard’ appear referring to this standard, they should be read as ‘Indian Standard’.

b) Comma (,) has been used as a decimal marker, while in Indian Standards, the current practice is to use a point (.) as the decimal marker.