An adapter sleeve is a tapered, slotted ring—usually made of hardened steel—that allows a bearing with a tapered bore to be mounted on a standard cylindrical shaft. The sleeve sits between the shaft and the inner race of the bearing. As the bearing is pushed up the taper, it tightens around the sleeve, locking securely in place.
Most adapter sleeves are used in conjunction with a lock nut and locking washer or tab washer to secure the assembly. This method ensures precise alignment and prevents axial displacement during operation.