Abstract: In through-feed centerless superfinishing of tapered rollers, an approximately symmetrical smoothed crown can be generated on the conical surface when the rollers feed through straightly with a fixed posture, but the crown generation mechanism not yet be revealed. For the fixed posture that the roller’s axial is just inclined at a fixed angle on the through-feed direction vertical plane, based on the characteristics of the superfinishing process as well as the geometric and kinematic relationship between the rollers and the oilstones, equations of the contact line between the roller and the oilstone as well as the longitudinal section profiles of the roller are established, and the formulas for computting the width of every superfinishing region is derived. Regarding this superfinishing process as a roller wear process in contact with the oilstone, and the crown as the result of the nonuniform roller wear, the crown generation mechanism is revealed as follows according to basic wear principle: there are four different superfinishing regions corresponding to the contact line with the pattern of “π”, and they make more wear at end part than the middle part of the roller; there are different inclination between the longitudinal section profiles of the roller, and they make the roller’s wear depth decrease gradually and nonlinearly from two end point to the middle point of the roller, so the crown is generated. The conclusions are drawn as follows: a symmetrical smoothed crown can be generated only when the roller’s top generatrix inclines at a proper angle with its small end rising up; the roller’s taper angle is the basis, and the crown can be generated only when the taper angle is not zero；the biggest crown generated is restricted by the magnitude of the taper angle, and the bigger the taper angle is, the bigger the crown is. The formulas that determine the range of the proper inclination angle of the roller’s top generatrix are derived .

Key words: Crown generation mechanism, Fixed posture, Tapered roller, Through-feed superfinishing