Abstract: A component of a crawler type machine is hardened by explosive depth hardening. The component is typically a crawler track shoe (10), and the roller path surface (11) of the track shoe and immediate underlying metal portion are pre-hardened by placing explosive charge (15) on the surface of the track shoe (10), and detonating the explosive charge to impart a high force on the surface and underlying metal portion for a short duration. The resultant shock wave causes high-velocity deformation at a high stress level, which leads to intensive development of plastic displacement at microscopic size. This increases the hardness and the strength of the surface and underlying metal portion. The surface (11) may be hardened by repetitive explosive depth hardening. Grooves (20) may also be formed in the roller path (11) to accommodate any flow of material.