PURPOSE: To stably pass and run the material by forming the caliber surface in R-type curve toward the outside on the VSB caliber roll formed the caliber on the outer circumferential surface of the circular tube like roll.

CONSTITUTION: The caliber 3 is formed on the outer circumferential surface of the circular tube like VSB (vertical scale breaker) roll 1. In order to make the shape to close the material going to incline in the caliber, the caliber surface 3a of the caliber 3 is made in the R-type curved toward the outside. This rate of curvature of this caliber surface is calculated with the size and the direction of the force applied to the material. The width X or the caliber surface is formed to the size which is a little larger than the sheet thickness Y of the material 2. Further, the depth H of the caliber is made larger than the depth of the former caliber. Therefore, the material going to incline is sealed forcibly and without tucking up of the end part of running material, the material can be stably passed and run.