The paper presents the results of model tests related to the process of forming a pipeline arc using the mechanical bending method with a new flexible mandrel design. The introductory section outlines the problems associated with the pipeline manufacturing process and the methods and tools used to shape bent pipeline sections, in particular the so-called mandrel bending. The shortcomings of the currently used cold pipe bending methods and the need to search for new solutions in this area are pointed out. The main part of the paper consists of the results of model tests of deformations and stresses resulting from the process of forming a mechanically bent pipeline arc using the proposed version of the mandrel, which has the properties of flexible adaptation to the shape of the formed pipe while maintaining radial stiffness. The model studies included an analysis of the values of deformations and stresses occurring in the cross-section of a bent pipe arc depending on changes in the design parameters of the flexible mandrel using the finite element method. Based on the obtained test results, the design parameters of the flexible mandrel were determined, thanks to which the stresses in the cross-sections of the bent pipe section caused using the mandrel are within the limits imposed by normative recommendations, while eliminating the ovalisation of the cross-section of the shaped pipe. This demonstrates the practical usefulness of the proposed flexible mandrel with a new design. The innovative nature of the proposed solution is determined by the fact that the mandrel is characterised by flexible susceptibility to bending deformation, while maintaining radial rigidity. The presented flexible mandrel also allows pipes to be shaped using traditional methods without the need for specialised and expensive mandrel bending machines.