Abstract: A core assembly for a continuous sheet includes a core of a cylindrical form. A side channel is formed in the core to extend fully in an axial direction thereof. A shaft hub is disposed through the core movably in the axial direction. A changing unit or adjuster displaces the core in response to moving of the shaft hub between first and second positions, and enlarges an outer diameter of the core when the shaft hub is in the second position than when the shaft hub is in the first position. Preferably, the changing unit includes a cam roller, disposed on the shaft hub, for projecting in a radial direction. A cam ramp surface is formed with an inner surface of the core, has a height increasing toward the second position, is pressed by the cam roller.