Common engineering solids usually have thermal expansion coefficients that do not vary significantly over the range of temperatures where they are designed to be used , so where extremely high accuracy is not required , calculations can be based on a constant , average , value of the coefficient of expansion . Common engineering solids usually have coefficients of thermal expansion that do not vary significantly over the range of temperatures where they are designed to be used , so where extremely high accuracy is not required , practical calculations can be based on a constant , average , value of the coefficient of expansion .