METHOD FOR CONTROLLING THICKNESS GAUGE

PURPOSE:To reduce the off-gauge length of a top part of steel sheet and to improve the yield of product, by turning on an AGC after selecting a timing of the lower limit capable of avoiding the breakage of sheet in accordance with the finished thickness gauge. CONSTITUTION:An AGC controlling system 5 is controlled by the deviation between the thickness gauge at the exit side of the final stand 1 and the target thickness gauge, and at the same time, the gauge of a steel sheet is controlled by driving a mill motor 7 driven by an ASR controlling system which is controlled basing on the system 5. In this case, the system 5 is turned on against the speed of sheet at the exit side of the final stand 1 in accordance with the finished thickness gauge measured by an X-ray thickness gauge 4 while keeping the speed to be within a range as shown by a dotted line in the figure where the sheet breakage is avoided. As a result, the AGC is turned on at the speed reversely proportional to the thickness of a material, and the off-length of a thick material is reduced.