This study examines the effects of various heat treatment processes on the dimensional tolerance of metallic materials. Firstly heat treatments such as annealing, normalizing, quenching, and tempering used to enhance mechanical properties like strength, hardness, and ductility were explained. These processes influence dimensional stability due to changes in the microstructure and the release or introduction of internal stresses. Techniques such as stress relief annealing and recrystallization annealing help mitigate dimensional distortions caused by prior deformation or machining. Surface hardening methods, including flame hardening, induction hardening, and cementation, are also evaluated for their impact on maintaining dimensional precision while improving surface hardness. The studies conducted to investigate the effect of heat treating on dimensional tolerances were summarized and finally dimensional tolerances changes of AISI 4140 material after the nitriding process were presented. This analysis highlights the importance of optimizing heat treatment parameters to achieve desired mechanical properties without compromising dimensional tolerances, which is critical for applications demanding high precision.