Selecting the right scrap steel requires understanding the ISRI (Institute of Scrap Recycling Industries) classifications. Buyers should distinguish between HMS 1 (Heavy Melting Steel), which consists of wrought iron or steel scrap ≥1/4 inch thick, and HMS 2, which is thinner. For high-precision manufacturing, Bonus Grade or Plate and Structural (P&S) scrap is preferred due to its higher density and lower impurity levels. Always request a chemical composition analysis to check for residual elements like copper, tin, or phosphorus, which can affect the quality of the final smelted product.