Metal Buying Glossary

Brass 260 is a 70/30 copper-zinc alloy known as cartridge brass. It has a rich gold color, excellent machinability, and polishes to a mirror finish. Standard for engraving plates, decorative hardware, signage, and knife furniture. Available in sheet and flat bar forms. Meets ASTM B36.

T6 indicates an aluminum alloy that has been solution heat-treated and then artificially aged to achieve peak strength. This is the most common temper for structural applications — it produces the highest strength in heat-treatable alloys like 6061 and 7075. T6 material is ready for immediate use in load-bearing applications.

Mill finish is the surface condition of metal as it comes from the rolling mill, with no additional finishing applied. It is the default finish for most aluminum, stainless steel, brass, and copper products. Mill finish is suitable for most fabrication applications and can be further finished by anodizing, polishing, brushing, or painting.

Extrusion and rolling are two primary methods for forming metal. Extrusion pushes heated metal through a shaped die to create complex cross-sections (angle, channel, tube, bar). Rolling passes metal between heavy rollers to produce flat products (sheet, plate). Extruded products are identified by alloy-temper (e.g., 6063-T52), while rolled products use the same convention (e.g., 5052-H32).

ASTM International (formerly the American Society for Testing and Materials) develops and publishes voluntary consensus standards for materials, products, systems, and services. In metals, ASTM specifications define chemical composition, mechanical properties, and testing methods. Common specs include ASTM B209 (aluminum sheet/plate), ASTM A240 (stainless sheet/plate), and ASTM B36 (brass sheet).

A Mill Test Report (MTR), also called a Material Test Report or mill cert, is a document issued by the producing mill that certifies the chemical composition and mechanical properties of a specific heat or lot of material. MTRs provide full traceability from the original melt and are required for quality-critical applications in aerospace, defense, and food processing.

Anodizing is an electrochemical process that creates a durable, corrosion-resistant oxide layer on aluminum surfaces. The oxide layer can be dyed in various colors and provides excellent wear resistance. 6063 aluminum produces the smoothest, most uniform anodized finish. Type II anodizing (sulfuric acid) is standard for architectural applications; Type III (hard anodize) provides a thicker, harder coating for industrial use.