Patent ID: 8166789

Claim:
A reducing mill including a plurality of stands disposed along a rolling direction line, wherein a pipe or tube is rolled through said plurality of stands along said rolling direction line, said stands each include n rolls, wherein n is equal to or greater than 3, disposed around said rolling direction line, said n rolls are disposed shifted by 180°/n around said rolling direction line from n rolls included in a preceding stand, each of said n rolls included in each of said plurality of stands excluding a last stand has a groove having an arch shape in cross section, a bottom of said groove having a circular arc shape having a first radius around said rolling direction line in cross section, a distance between a surface of a roll flange portion positioned between the bottom and an edge of said groove and said rolling direction line is longer than said first radius, and a distance between the edge of said groove and said rolling direction line is longer than the first radius in the groove of a roll included in said preceding stand.