A thin-walled spherical shell made of pure iron material is a key part of precision physical experiments. Tool wear is an important factor restricting its geometric accuracy. And tool wear characteristics of curved surface parts are significantly different from those of single-point turning due to the movement of the contact point between the tool and the workpiece. Hence, this article takes the pure iron spherical shell as the research object, which is aimed at investigating the formation mechanisms of flank wear land. Tool wear characteristics are compared between spherical shell turning and end face turning. The results show that uniform flank wear land and notable notch wear occur when turning end face, but notch wear disappears and only flank wear land exists when turning spherical shell. Based on major notch position and minor notch position, a mathematical model is developed to explain formation mechanisms of flank wear land during turning spherical shell of pure iron materials. Theoretical and experimental results show that flank wear land results from the major and minor notch movement. Spherical shell turning and end face turning have the same wear mechanisms, mainly composed of adhesive wear, diffusion wear and oxidation wear.