The purpose of this study is to evaluate the effect of mild steel as dummy with various heights on the inductance value of core. The experiment is performed according to standard operation procedure used in VACUUMSCHMELZE (M) SDN. BHD. (VAC) production line and all parameters such as core weight, tension of core and temperature process are controlled based on the actual practice for specific core production. The VITROPERM 500 (Fe–Cu–Si–X) strip was used as the main material and the magnetic field annealing process was carried out using magnetic field annealing furnace. As for the inductance value measurement, a UNITESTER test machine which developed by VAC was used to measure the inductance value for each core after the heat treatment process for 12 h duration. Prior to the annealing process, a test on the magnetic field strength inside the furnace was done to check the strength of magnetic field where the data indicate a non-linear strength along the furnace, which is the strength will be greater at the middle (1.85 kA/cm) and lowest at the bottom of the furnace (1.70 kA/cm) where the cores is placed. Quantitative analyses showed the inductance value of bottom core decreased greater than 10% as compared to the neighboring core with the absence of the mild steel. One should keep in mind that the value for the tested cores is not specified, only the deviation of the inductance value of bottom core will be considered. This phenomenon occurred due to the attraction strength of bottom dummy towards the magnetic field. Further experiment was done to evaluate the effect of different height of mild steel and it is worth to note that various height of mild steel does not gives any significant effect on the inductance value of core.