PURPOSE: To adjust inner diameter of a roll for determining diameter of a can drum easily and quantitatively by forming a jig for seam welding to thickness and width sufficiently lower in rigidity than the roll for determining diameter of can drum and to annular shape having a slit.
CONSTITUTION: The annular jig 8 is provided with a slit of fixed width L and its thickness is so determined that the rigidity becomes low enough to be negligible compared with that of the roll for determining diameter of can drum. A displacement gauge 9 corresponds to a clip gauge mounted in the slit, and diameter of the jig 8 can be grasped quantitatively by measuring the width L of the slit by the gauge 9. Inner diameter of the roll for determining diameter of can drum can be obtained easily by inserting the jig 8.
KABASAWA MAKOTO