Evaluation of cutting fluids by consumption energy in tapping test

This paper describes the usefulness of the tapping test by introducing the concept of consumption energy, which is estimated by the integration of the total torque-time curve, as an alternative to the tapping torque which is commonly used to evaluate cutting fluids. In the theoretical analysis of the tapping torque, factors which contribute to the torque are the coefficient of friction and the stress required to break a machined material on the rake face of a tap. The reduction of the former factor has been considered to be important as the principal role of cutting fluids. However, the theoretically obtained contribution of the coefficient of friction on the tapping torque is small in comparison with that expected from the measured tapping torque. It is pointed out that the cutting fluids influence the overall cutting process rather than the mere reduction of friction on the rake face. By using consumption energy, it is possible to take account of the overall cutting process. More precise evaluations can be made since the cutting characteristics of the fluids appear clearly in the portion after the maximum of the measured torque-time curve, and that portion corresponds to the process after the cutting edges of a tap pass through the machined material.