Excerpt from Machine Design: Hoists, Derricks, Cranes The remaining part will be soft and easily machined. The chilling is effected by using iron sections faced with a light coat ing of loam at the points to be chilled. Iron car-wheels are made in this way, thus giving a chilled tread to resist wear, while the hub is soft, permitting of easy boring for the axle. The thickness of the chilled portion may vary from inch to 78 inch or more, depending upon the iron mixture and the method of chilling.