Abstract: A method of casting an object, usually a railroad wheel, is provided. A graphite mold having a drag section and a cope section requires a plurality of riser openings in the cope section to ensure proper dimensional accuracy of the cast railroad wheel by allowing molten metal to continue to feed downwardly through the riser openings to the cast wheel cavity during initial cooling. The riser openings are lined with an improved insulating material in an accurate manner such that the insulating material is added between a machined riser opening in the graphite cope mold section and a mandrel inserted in the riser opening.