EE was installing a 6.5 X 6.5 square steel tubing core over shaft of a belt winder. EE and coworker placed the winder shaft onto cribbing and placed the core over end of shaft and proceeded to push core onto shaft. As core slid onto shaft ee pinched his left ring finger between core and shaft. Fractured bone in finger tip and laceration, 8 stitches to close wound.