This study focuses on the refinement of the deformation zone scheme during the deforming broaching of workpieces made of plastic materials under conditions of through plastic deformation. For this purpose, a methodology for analyzing the stress-strain state during the deforming broaching of workpieces made of plastic materials was developed. It is established that when the critical contact pressure arises in the contact zone, certain modifications occur in the known deformation zone scheme. When the contact pressure remains below the critical threshold, the deformation zone scheme corresponds to the known one. It is shown that the emergence of the critical contact pressure corresponds to the critical wall thickness, with its value depending on the tension in the element and the inclination angle of the working element's generative surface. The dependence for its determination is obtained. The presence of critical contact pressure in the contact zone leads to changes in the deformation zone scheme. Local plastic deformation zones appear at the boundaries of the contact area. These zones result in an increase in the contact zone and a decrease in the height of the out-of-contact zone behind the contact area. Additionally, they enable control over the shape of the workpiece, allowing to achieve the required circumferential and axial deformations by selecting the broaching modes and tool geometry. The findings of this study were applied to develop a technology for the restoration of worn piston pins using deforming broaching. The implementation of this technology at a single enterprise saved 4.5 tons of metal per thousand machined parts.