The surface hardness test was measured by Matsuzawa DXT3 Rockwell test device according to the ISO standards, this was done to determine the hardness of the various heat treated springs. The water quenched spring was subjected to an incremental load of 4 kg and an extension of 0.15 cm was measured until an extra load of 4 kg was added to the 16 kg mass and an extension of 0.3 cm was measured, which indicated that 16 kg was the yield load of the water quenched springs, similarly the yield load of the normalized and as received springs can be obtained from Section 3 (Result and Discussion).