Dimensional Accuracy: Precision machining typically requires IT5-IT7 grade (ISO standard). For example, the tolerance of aero-engine blades needs to be controlled within ±0.005mm (refer to the *Machining Handbook*). High-precision parts, such as optical lens frames, even require IT3 grade, necessitating the use of ultra-precision lathes or grinders.
Surface Roughness: The Ra value of critical components (such as hydraulic valve cores) needs to be ≤0.4μm, achieved through fine grinding or polishing; for ordinary precision parts, Ra within 1.6μm is sufficient. Research shows (*China Mechanical Engineering*, 2022) that for every 0.1μm reduction in surface roughness, the fatigue life of a part can be increased by 15%-20%.
Geometric Tolerances: These include roundness and cylindricity. For example, the roundness error of high-precision bearings needs to be ≤0.001mm, requiring real-time detection using a coordinate measuring machine (CMM).
