Introduction

0.1 ISO/R 76:1958

ISO/R 76, Ball and Roller Bearings — Methods of Evaluating Static Load Ratings, was drawn up by Technical Committee ISO/TC 4, Ball and Roller Bearings.

ISO/R 76 was based on the studies of A. Palmgren et al^[²^],[³^]. The basic static load ratings were defined to correspond to a total permanent deformation of rolling element and raceway at the most heavily stressed rolling element/raceway contact of 0,000 1 of the rolling element diameter. Then the standard values confined to the basic static load ratings for special inner design rolling bearings were laid down.

ISO/R 76:1958 was approved by 28 (out of a total of 38) member bodies and was then submitted to the ISO Council, which decided, in December 1958, to accept it as an ISO Recommendation.

0.2 ISO 76:1978

ISO/TC 4 decided to include the revision of ISO/R 76 in its programme of work and ISO/TC 4/SC 8 secretariat was requested to prepare a draft proposal. As a result, the secretariat submitted a draft proposal^[³^] in January 1976.

The draft proposal was accepted by 6 of the 8 members of ISO/TC 4/SC 8. Of the remaining two, Japan preferred further study and USA, its counter proposal, document ISO/TC 4/SC 8 N 64^[⁴^]. The draft was then submitted to the ISO Central Secretariat. After the draft had been approved by the ISO member bodies, the ISO Council decided in June 1978 to accept it as an International Standard.

ISO 76:1978 adopted the SI unit newton and was revised in total, but without essential changes of substance. However, values of X₀ and Y₀ for the nominal contact angles 15° and 45° for angular contact groove ball bearings were added to the table to calculate the static equivalent radial loads of radial ball bearings (see ISO 76:1978, Table 2).

0.3 ISO 76:1987

During the revision of ISO/R 76:1958, USA had in 1975 submitted a counter proposal^[⁴^] for the basic static load ratings based on a calculated contact stress.

The secretariat requested a vote on the revision of the static load ratings based on a contact stress level in January 1978 and afterward circulated the voted results in June 1978, and the item No. of revision work had become No. 157 of the programme of work of TC 4.

ISO/TC 4/SC 8, considering the proposals made in the documents TC 4/SC 8 N 75^[⁵^] and TC 4 N 865^[⁶^], as well as the comments made by TC 4 members and that several SC 8 members expressed a need for updating ISO 76, agreed to continue its study taking into account the possibility of using either permanent deformation or stress level as a basis for static load ratings, and ISO/TC 4/SC 8 requested its secretariat to prepare a new draft. The new draft was intended to be prepared with the principles and formulae of the document TC 4/SC 8 N 75, and to include levels of contact stress for various rolling element contact stated to be generally corresponding to a permanent deformation of 0,000 1 of the rolling element diameter at the centre of the most heavily stressed rolling element/raceway contact. For roller bearings a stress level of 4 000 MPa was agreed and then ISO/TC 4/SC 8 agreed, by a majority vote, that static load ratings should correspond to calculated contact stresses of

	4 000 MPa for roller bearings,
	4 600 MPa for self‑aligning ball bearings, and
	4 200 MPa for all other ball bearings to which the standard applies.

For these calculated contact stresses, a total permanent deformation occurs at the centre of the most heavily stressed rolling element/raceway contact, and its deformation is approximately 0,000 1 of the rolling element diameter.

ISO 76 was submitted to the ISO Central Secretariat in 1985, and after it had been approved by the ISO members, the ISO Council decided in February 1987 to accept it as an International Standard.

Furthermore, ISO/TC 4/SC 8 decided that supplementary background information, regarding the derivation of formulae and factors given in ISO 76, should be published as a Technical Report. This Technical report was published as ISO/TR 10657:1991.

An Amendment to ISO 76:1987 that explains the discontinuities in load ratings between radial- and axial bearings was published as ISO 76:1987/Amd.1:1999.

0.4 ISO 76:2006

A systematic review of ISO 76:1987 was agreed in 2003, based on the prior held balloting process and documents TC 4/SC 8 N 233 and N 235.

ISO 76:2006 includes editorial adaptations and updates as well as an extension by the static safety factor S₀. Furthermore, ISO 76:1987/Amd.1:1999 was integrated and became the informative Annex A “Discontinuities in the calculation of basic static load ratings”.

0.5 ISO 76: 2006 /Amd.1:2017

ISO 76:2006/Amd.1:2017 includes the following items:

— graphs for the factors f₀, X₀ and Y₀ taken from draft ÖNORM M 6320 to be included in an informative annex;
— formulae for the calculation of the load rating factor f₀ from ISO/TR 10657 to be introduced in the normative part of the standard;
— the tables for the load rating factor f₀ will stay in the normative part of the standard, however a sentence will be introduced stating that the results obtained from formulae are preferred.

PD ISO/TR 10657:2021

Explanatory notes on ISO 76

Current

Published:

30 Nov 2021