How we improve our machining precision?

We all know that machining accuracy and machining tolerance are both terms to evaluate the geometric parameters of the machined surface.  The machining precision is measured by tolerance level, the smaller the value is, the higher the precision will be; machining tolerance is expressed by numerical value, the larger the value is, the larger the tolerance will be.
There are 20 tolerance levels from IT01, IT0, IT1, IT2, IT3 to IT18, of which IT01 means that the part has the highest machining precision, IT18 means that the part has the lowest machining precision, and generally IT7 and IT8 are medium machining precision levels.
The actual parameters obtained by any machining method will not be absolutely accurate. From the function of the part, as long as the machining tolerance is within the tolerance range required by the part drawing, it is considered that the machining accuracy is guaranteed.
But we can still do the below jobs to improve our machining precision.
1. By test cutting - measuring the size - adjusting the tool - cutting - test cutting again, and so on and so forth until the required size is reached. This method has low production efficiency and is mainly used for single-piece small batch production.
2. The required dimensions are obtained by pre-adjusting the relative positions of the machine, fixture, workpiece, and tool. This method is highly productive and is mainly used for mass production of large quantities.
3. Choose high precision rolling bearing, use high precision multi oil chisel dynamic pressure bearing and high precision static pressure bearing, improve the machining accuracy of the box support hole and spindle journal, and the machining accuracy of mating surfaces with bearings, measure and adjust the radial runout range of the corresponding parts to compensate or offset the error, proper preload of rolling bearings, reduction of drive chain transmission errors.
4. The tool will be resharpened before it reaches the rapid wear stage.
We'll constantly focus on improving the process precision as much as possible.