精密机械加工是在严格控制的环境条件下，使用精密机床和精密量具和量仪来实现的。加工精度达到和超过 0.1微米称超精密机械加工。在航空航天工业中，精密机械加工主要用于加工飞行器控制设备中的精密机械零件，如液压和气动伺服机构中的精密配合件、陀螺仪的框架、壳体，气浮、液浮轴承组件和浮子等。飞行器精密零件的结构复杂、刚度小、要求精度很高，而且难加工材料所占的比重较大。
精密机械加工的工艺效果是：
①零件的几何形状和相互位置精度达到微米或角秒级；
②零件的界限或特征尺寸公差在微米以下;
③零件表面微观不平度(表面不平度平均高度差)小于0.1 微米;
④互配件能满足配合力的要求；
⑤部分零件还能满足精确的力学或其他物理特性要求，如浮子陀螺仪扭杆的扭转刚度、挠性元件的刚度系数等。
Precision machining is achieved using precision machine tools, measuring tools, and instruments under strictly controlled environmental conditions. Precision machining with a processing accuracy of 0.1 microns or more is called ultra precision machining. In the aerospace industry, precision machining is mainly used to process precision mechanical parts in various parts of the actuator control system, such as precision fittings in hydraulic and pneumatic servo mechanisms, frames and shells of gyroscopes, air and liquid floating bearing components, and floats. The structure of precision parts for aircraft is complex, with low stiffness and high precision requirements, and a large proportion of difficult to machine materials.
The process effect of precision machining is:
① The geometric shape and mutual position accuracy of the parts reach the micrometer or arcsecond level;
② The boundary or characteristic dimension tolerance of the parts is below micrometers;
③ The micro roughness of the part surface (average height difference of surface roughness) is less than 0.1 micrometers;
④ Mutual accessories can meet the requirements of mating force;
⑤ Some parts can also meet precise mechanical or other physical property requirements, such as the torsional stiffness of the float gyroscope torsion bar and the stiffness coefficient of the flexible element.
