120mm Wire 1-8mm rollers. Case hardened and accurately trued. Rockwell hardness 63/65 Rolling Precious Metal Into Plate. In order to prepare gold, platinum, and other precious metals for jewelry making, it is necessary to create basic shapes and forms. To do this, barred ingots of precious metal are rolled through mills to attain bars, rods, and sheets in the desired gauges needed to craft jewelry. After each pass through the mill, the rollers are reset to a narrower gauge. After several passes through the mill, the metal must be reheated to cherry red and annealed in order to soften it and keep it from becoming brittle.