Today the spherical coordinate system is widely used in the study of the drawing stress–strain state. The spherical boundaries hypothesis of the deformation zone test in the cold drawing process of electrical copper wire on a coarse drawing mill was performed. It was found that at the exit of the deformation zone borders form are close to radial, however the boundary has a different shape at the entrance to the deformation zone. The deformation zone is divided into two halves with localization of the velocity intensities in the annular zones which may cause the wire structure inhomogeneity.