A high efficiency grinding machine for grinding the pin on a crankshaft has a machining space with a grinding wheel mounted on the lower end of an arm to form a pendulum assembly. A headstock supports the crankshaft in the machining space. A pivot drive rocks the pendulum assembly back and forth equal distances about the equilibrium position causing the grinding wheel to follow the non-circular path of a pin as the crankshaft as it is rotated about its elongated axis.