A laboratory quenching kit apparatus was designed and fabricated using the dimensions, which are within the calculated design limits. The testing of the fabricated quenching kit apparatus was carried out using the standard specimens of 25 mm diameter and two other specimens of lower diameters: 20mm and 15 mm, all made from medium carbon steel. The hardness test was also carried out on the quenched samples. It was found that the hardness of the samples varied with their dianicters. Also the greater the surface area of the sample, the more the martensite formed. This invariably made the sample to be harder.