Our factory uses the existing M4215 honing machine to honing the connecting rod small hole of a diesel engine (Fig. 1). The drawing requires a surface roughness R_z6.3 of φ40_0~(+0.016)mm. Due to the small diameter of the workpiece, it is not possible to directly use the honing head of the original machine tool. To this end, I designed a honing head for honing the small hole of the connecting rod.