The invention relates to a method for preparing the surface of a substrate (100) for the purpose of accepting and holding a coating sprayed by a plasma torch. Said method includes a machining phase and is characterized that it includes the following phases: producing, by means of a machining tool (200), at least one groove having at least one angled edge; offsetting the tool (200) by moving the tool relative to the surface of the substrate (100) in a direction perpendicular to the longitudinal axis of the groove and along a path shorter than the projected length of the angled edge; and using said tool (200) on the angled edge of the groove such as to subject said edge to stress and create another offset groove, and so on and so forth, such that the tool (200) irreversibly changes the shape of the ribs (111, 112, 113, 114) finally obtained between each groove, and said ribs adopt undercut surfaces.