When sourcing mechanical parts, the material grade is the most critical factor. You must verify the chemical composition and mechanical properties (such as tensile strength and hardness) against international standards like ASTM, DIN, or ISO. For precision components, ensure the supplier provides a Material Test Report (MTR) or a Mill Test Certificate (MTC). Additionally, confirm dimensional tolerances (e.g., +/- 0.01mm) using technical drawings in CAD or STEP formats to ensure compatibility with your existing machinery.