A portable printer is provided having a housing with a compartment for a roll of media and two spindle members coupled to roll positioning mechanism in the compartment. Each spindle member has tow sides with different diameter conical surfaces and is reversibly mountable in the printer to select such conical surface having a diameter for engaging the core diameter of a roll mounted between the spindle members. Each of the spindle members is reversible in the printer to enable presentation of two different diameter conical surfaces for engaging two different diameter roll cores in the printer. The conical surfaces can also reshape the ends of a crushed roll core from a oval to a circular cross-sectional shape when the spindle members are urged towards each other by the roll positioning mechanism into the ends of the roll core, thereby providing for proper rotational mounting of such roll in the printer.