Abstract In single-shot hardening applications, heat treated components often feature a variety of geometric complexities including variable wall thicknesses, sharp diameter transitions, lightening holes, slots, etc. Due to the inherent 3D electromagnetic nature of single-shot coils and the complex geometry components which they must accommodate, the design and optimization of single-shot hardening coils is typically a demanding and intricate task. This paper presents combined electromagnetic-thermal and thermal-mechanical FEA simulation results for the single-shot induction hardening of a power transmission shaft. The simulation results, including electromagnetic, thermal, metallurgical, and mechanical data demonstrate the value of computer simulation in the design and development of single-shot induction hardening systems.