Abstract: An assembly for making a wax pattern of a hollow component includes a pattern die and a noncircular core which is located within the pattern die. The pattern die is a split die and includes two halves which have shaped internal surfaces to define the external shape of the wax pattern of the hollow component. The core has shaped external surfaces which define the internal shape of the wax pattern of the hollow component. The core has coaxial circular cross-section projections which locate within correspondingly shaped and dimensioned apertures in the pattern die. One of the apertures in the pattern die has a radially extending pin which is arranged to mate in a groove on the projection to locate the core longitudinally. The core is allowed to rotate within the die so that chaplets on the core position the core accurately without imposing strains on the core.