Aluminum alloy has low density and low cutting resistance, which reduces the load on cutting tools and allows higher feed rates and spindle speeds. This results in high machining efficiency and easy control of surface roughness. For thin parts, complex curved surfaces, or parts requiring subsequent anodizing, aluminum alloy is the first choice. However, aluminum alloy has relatively low rigidity; if the fixture design and cutting parameters are not appropriate, deformation can easily occur. When requesting a quote, be sure to specify whether anodizing, sandblasting, or painting is required, as these downstream processes affect the tolerance allowance.

Stainless steel is commonly used for parts requiring corrosion resistance, high strength, or medical-grade applications, but its work hardening characteristic causes the material to harden rapidly in the cutting zone, leading to shortened tool life and increased surface scratches. In practice, CNC machining of stainless steel requires lower cutting speeds, a stable coolant supply, and machining allowances reserved for secondary finishing. If buyers specify stainless steel, they should also provide the hardness grade (e.g., 304, 316, 17-4PH) and heat treatment condition, as these directly affect achievable tolerances and pricing.

Brass (including copper) has low cutting resistance and produces short chips, resulting in less tool wear, making it a common material for Swiss-type lathes and precision turned parts. Brass has a good surface finish, and many parts can be shipped in their natural color, saving downstream processing costs. Note that brass has moderate rigidity, so thin-walled parts still require fixture design to control deformation. If buyers use it for conductive, heat dissipation, or appearance parts, they should specify the application and conductivity requirements, allowing the machining shop to recommend the appropriate grade.