A device for expanding a hollow body includes a plurality of sector-shaped expandable jaws disposed in a holder and distributed about a central axis. The expandable jaws extend along the axis to a free end and are radially movable with respect to the axis. Each of the expandable jaws includes: a cylindrical surface having a radius corresponding to a radius of the expanded hollow body and an inward radial taper at an area of the free end； and a plurality of projections and recesses disposed in a joint region and arranged in an alternating manner with each other along the axis and at least partially extending into the area of the free end. The cylindrical surfaces are rounded off to transition to respective outer surfaces of the projections. The outer surfaces of the projections extend, at least at ends of the projections, radially inward with respect the cylindrical surfaces.
