Methods of manufacturing sheet film forming rolls

A method of manufacturing a sheet film forming roll comprising:

• processing a thin cylindrical work used as an external cylinder of the sheet film forming roll, by a method including holding the thin cylindrical work using a holding jig for the thin cylindrical work and machining an outer peripheral surface of the thin cylindrical work being held, the holding jig including:
• a holding member made of a metal and having a cylindrical shape and an elastically expandable or contractible diameter, the holding member configured with an outside diameter of the holding member being held smaller than an inside diameter of the thin cylindrical work for insertion of the holding member into an inner periphery of the thin cylindrical work and being expanded after insertion of the holding member into the inner periphery of the thin cylindrical work to hold the thin cylindrical work from an inner peripheral side of the thin cylindrical work with an outer peripheral surface of the holding member in close contact with an entire inner peripheral surface of the thin cylindrical work;
• a diameter changing unit configured to apply either:
• an axial external force in a compressing direction to both ends of the holding member to change the diameter of the holding member,
• an axial external force in a tensile direction to both ends of the holding member to change the diameter of the holding member, or
• an axial external force in a tensile direction and then an axial external force in a compressing direction to both ends of the holding member to change the diameter of the holding member;
• and
• a pair of circular side plates each including outer peripheral portion fixed to an opposite end of the holding member respectively;
• wherein the diameter changing unit is provided between the pair of circular side plate, and wherein the diameter changing unit includes:
• a plurality of rods provided between the pair of circular side plates;
• and
• a screw mechanism configured to apply either a tensile force or a compressing force to each of the rods by rotation of a screw in order to apply either the axial external force in the compressing direction or the axial external force in the tensile direction to the both ends of the holding member via the circular side plates via a reactive force of the tensile force or the compressing force.