Abstract: A two-tiered punch having an extending imprint head with impact surfaces is employed to deform the top threads of a clinch-type nut during installation to create a lock-type nut. As the deforming imprint is applied, a shoulder on the punch supplies the installation pressing force against the top face of the nut. As the imprint head moves downward into the material of the nut, portions of the top thread are deformed, being compressed axially downward. The size of the imprint head and the distance that the imprint head projects from the shoulder determines the depth of imprint deformation and, hence, the degree of thread deformation. The imprint head is centered on the nut thread and is configured in the shape of a polygon extending from the face of the punch. During deformation and installation, the nut is held in a center position with regard to the coining edges of the imprint head by a centering pin which extends from the end face of the punch.