When discussing 42, 57, and 86 stepper motors, it refers to their sizes, corresponding to the NEMA (National Electrical Manufacturers Association) standard sizes: NEMA 17, NEMA 23, and NEMA 34. These numbers represent the standard dimensions of stepper motors, with main differences in size, power output, and application scenarios.

1. NEMA 17 (42 Stepper Motor):

   • Size: The NEMA 17 stepper motor has dimensions of 42mm × 42mm, making it a smaller-sized stepper motor.
   • Application: It is suitable for small-scale devices or applications with strict space requirements, such as 3D printers, small CNC machines, precision instruments, etc.

2. NEMA 23 (57 Stepper Motor):

   • Size: The NEMA 23 stepper motor has dimensions of 57mm × 57mm, falling into the medium-sized stepper motor category.
   • Application: Widely used in automation equipment, CNC machine tools, packaging machinery, and other applications with medium power and precision requirements.

3. NEMA 34 (86 Stepper Motor):

   • Size: The NEMA 34 stepper motor has dimensions of 86mm × 86mm, making it a larger-sized and higher-powered stepper motor.
   • Application: Commonly used in large-scale mechanical equipment, industrial automation equipment, laser equipment, etc., with high power and load requirements.

In summary, the differences between the 42, 57, and 86 stepper motors lie primarily in their size, power output, and application scenarios. When selecting a stepper motor, it is essential to consider specific application requirements and space limitations to choose the most suitable size and model.