The invention relates to a reel mandrel (1) comprising radially mobile expansion segments (2) and/or closing strips (4, 13) arranged on the periphery thereof. According to the invention, the reel mandrel (1) is provided with axially arranged guiding grooves (12) on the periphery thereof, and the expansion segments (2) are provided with ribs (6). The invention further relates to a method for fixing and/or maintaining an expansion segment (2) and/or a closing strip (3, 13) on a reel mandrel (1).