Machining centers, lathes, and milling machines are three types of equipment commonly used in mechanical processing. They have some obvious differences in working principles, scope of application, and processing methods.

1. Processing methods and principles:
Lathe: Lathes are mainly used for processing rotationally symmetrical workpieces. The workpiece rotates on the spindle and the tool cuts on the workpiece. Lathes are suitable for processing outer circles, inner circles, end faces, tapers, threads, etc.
Milling machine: Milling machine is mainly used for cutting on the workpiece. The cutting tool moves in multiple axes, which can realize the processing of planes, curved surfaces, grooves, holes, etc.
Machining Center: A machining center is a multi-functional machine tool with multiple work axes that can perform the functions of a milling machine and a lathe. It can perform cutting in multiple axes, including plane milling, three-dimensional milling, hole processing, thread processing, etc., and is suitable for high-precision processing of complex workpieces.

2. Scope of application:
Lathe: Mainly used for processing rotationally symmetrical workpieces, such as shaft parts, bushings, etc.
Milling machine: It is suitable for workpieces of various shapes and can perform complex processing such as flat surfaces, curved surfaces, slots, and holes.
Machining center: suitable for complex, multi-faceted workpieces, especially parts that require high precision, high efficiency and multi-process processing.

3. Processing accuracy and degree of automation:
Lathe: The processing accuracy is average and it is suitable for workpieces that do not require particularly high accuracy.
Milling machine: The processing accuracy is higher and can meet more stringent accuracy requirements.
Machining center: It has high machining accuracy and can realize automated processing. The machining process can be automatically completed through CNC control system programming.

4. Processing characteristics:
Lathe: Mainly rotating, machining center cuts during the turning process, usually used for processing cylindrical workpieces.
Milling machine: Mainly cutting, the workpiece is stationary, and the cutting tool moves in multiple axes, which can realize complex processing.
Machining center: Mainly multi-axis cutting, capable of cutting in multiple directions, including planes, elevations, inclined surfaces, etc.

In general, lathes are suitable for processing rotationally symmetric workpieces, milling machines are suitable for plane and curved surface processing, and machining centers are multi-functional machine tools that can complete the functions of lathes and milling machines and are suitable for high-precision multi-faceted processing of complex workpieces.