Which of the following materials has the maximum shrinkage allowance ?

ANS:C - Lead

Among the options provided, lead typically has the maximum shrinkage allowance. Shrinkage allowance refers to the additional dimensions added to a pattern to compensate for the shrinkage that occurs during the solidification and cooling of molten metal in the casting process. Different metals have different rates of shrinkage, which is influenced by factors such as their thermal conductivity, specific heat, and phase transformation during solidification. Lead has one of the highest coefficients of thermal expansion among common casting metals, which means it experiences significant shrinkage as it cools from its molten state to its solid state. Therefore, lead typically requires the largest shrinkage allowance compared to materials like brass, cast iron, and aluminum alloy. It's important to note that the specific shrinkage allowance required may vary depending on factors such as the complexity of the casting, the casting method used, and the desired dimensional accuracy of the final product.