In this paper an experiment of cutting S 45 C steel is conducted by using a triangular pyramidal diamond single grain to analyse the mechanism of face grinding. The motions of the cutting edge and the work are reversed and a new type of dynamometer with a structure of parallel beams is used. The performance of this dynamometer is described in detail and a few results are reported which are obtained in this method. The results are as follows :
(1) The grinding force equation can be expressed as F=K·g1.5, where F is either the tangential force or the normal force, g the cutting depth and K a constant in cutting.
(2) The resistance force in cutting by the flat face of the pyramid is equal to that in ploughing by the sharp leading edge and the one in oblique cutting by the slant face is larger than those.
(3) The grinding force is inclined to increase slightly or to be almost constant as the grinding speed increases.
