The main technological functions of ultra-precision grinding are as follows: 

Reducing raceway roughness: During ultra-precision grinding, the grinding stone primarily acts on the peaks of the raceway, not the valleys. With good grinding quality, the ultra-precision margin is typically 3-5 μm. 

For heavy-duty bearings, the raceway roughness can be reduced to Ra0.25 or Ra0.4 after ultra-precision grinding. Reducing roughness helps slow raceway wear, decrease frictional resistance, and improve fatigue strength, thereby extending bearing life. Furthermore, lower roughness also improves corrosion and chemical resistance. 

Reducing raceway waviness: The grinding stone makes surface contact with the raceway, and its contact arc is larger than the wavelength of the workpiece surface waviness. This effectively removes the waviness peaks (eliminating only one side of the peak, without affecting the valleys), thus reducing waviness and minimizing vibration and noise during high-speed bearing operation. Improving raceway shape profile: The grinding stone reciprocates and oscillates according to the theoretical profile of the raceway cross-section. Through the grinding action of the fine abrasive, it effectively corrects the local raceway shape, improving it by approximately 30%. 

This helps optimize the stress distribution on the raceway and improve the bearing's load-bearing capacity. Forming an ultra-precision compressive stress layer on the raceway surface: The raceway surface after grinding often has a tensile stress layer with low hardness, making it prone to fatigue spalling. Ultra-precision grinding, through the reciprocating oscillation and pressure of an oilstone, generates residual compressive stress on the surface, resulting in a denser structure and thus enhancing the raceway's fatigue resistance and spalling resistance. Improving the quality of the oil film on the raceway surface: By removing surface peaks and reducing roughness, the oil film thickness and λ ratio can be increased, enhancing lubrication, reducing friction, and ensuring the stability of the oil film between the raceway and rolling elements. 

This helps to lower operating temperatures and extend service life. Improving the cleanliness of the raceway surface: Lower roughness makes it less likely for grinding debris and stains to remain, facilitating cleaning and thus improving the raceway's resistance to rust and chemical contamination, reducing wear, and further extending bearing life.