INTRODUCTION

This Item provides charts and calculation methods for determining the minimum lubricant film thickness in concentrated contacts that occur, for example, in rolling bearings and gears; in such contacts, often called Hertzian contacts, the nominal contact area increases with applied load.

For the purpose of calculating the lubricant film thickness, Hertzian contacts are regarded as either two-dimensional, with nominally line contact, or three-dimensional, with nominally point contact. Nominally line contact occurs in, for example, roller bearings, roller followers on cams and spur gears while three-dimensional contacts occur in, for example, ball bearings. The charts and calculation methods presented in this Item apply to two-dimensional contacts. It is frequently possible to obtain guidance on some three-dimensional contacts using these methods (see Section 4).

The text of this Item is divided into three main parts. The first part (Section 3) describes the operation of a lubricated Hertzian contact. The second part (Sections 4 and 5) gives guidance on the specification of the design parameters, identification of the regime of operation and determination of the film thickness. The final part gives guidance on ensuring that the contact will operate with an adequate margin of safety.