Experimental and statistical design considerations for economical evaluation of metalworking fluids using the tapping torque test

摘要

Recently, multiple evaluation systems (MES) that allow for a large number of tapping torque tests (T{sup}3) to be performed on a single workpiece have been gaining in popularity for the evaluation of metalworking fluids (MWFs). However, MWF formulators have had difficulty obtaining statistically significant results or results consistent with experience in the field, raising questions about the efficacy of MES. This paper develops statistical and experimental design considerations for MWF evaluation by MES that aim to maximize the sensitivity of T{sup}3 to MWF performance and to improve the correlation between laboratory and field performance. Toward this end, a metric of resolving power is developed that quantifies the ability of a T{sup}3 operating condition (speed, material, tool size, etc.) to discriminate between MWFs. It is shown that as resolving power increases, the correlation of T{sup}3 response to expected field performance increases. The paper concludes with a discussion regarding economic trade-offs between increased cost, resolving power, and statistical significance of T{sup}3 results.