LUBRICATING PROPERTIES OF GRINDING FLUIDS .2. COMPARISON OF FLUIDS IN 4-BALL TRIBOMETER TESTS

The traditional four-ball tribometer tests, although disputed in principle, are used in practice as a supplementary tool for comparison and preliminary evaluation of cutting and grinding fluids. Little of the information obtained in such tests is published, and four-ball machine data, especially on water-based fluids and on grinding, are scarcely available. However, a relatively simple, reproducible, cheap and reasonably informative technique is still needed to study lubricating effects in grinding. If the possibility of using tribometer tests for this purpose has to be studied systematically, a sufficient amount of data has to be accumulated. This paper presents four-ball machine data of fluids evaluated in previous studies of the present authors by surface-grinding experiments. Two different four-ball tribometers are employed to determine respectively the extreme-pressure and antiwear properties of the grinding fluids. The four-ball tests provide useful information on the eventual mechanisms of the lubricating behaviour of the fluids, relevant to grinding. However, for correlation studies, rheological and cooling properties at least should also be considered.