Roughness is a numerical value used to describe the degree of surface roughness of a product during mechanical processing. These values (such as 0.8, 1.6, 3.2, 6.3, 12.5) represent the average distance or height between the peaks and valleys on the surface of the part, and are explained as follows:

Roughness 0.8: This refers to the roughness value of the surface of an object, indicating that after machining, it is difficult to see obvious machining marks on the surface, but the machining direction can still be slightly distinguished. To achieve this level, precision machining is usually required, such as precision turning, planing, grinding, scraping, etc.

Roughness 1.6: This is also a numerical value that describes the surface processing state of an object. In this state, the surface machining marks are difficult to detect and can only be slightly distinguished from the machining direction. The smaller the surface roughness, the smoother the surface, which has an important impact on the performance of mechanical parts such as fitting properties, wear resistance, fatigue strength, etc.

Roughness 3.2: The absolute average roughness of the part surface relative to the reference is 3.2 microns. The surface smoothness at this level is already very good, equivalent to the precision of mechanical machining.

Roughness 6.3: This value is commonly used to describe the surface roughness obtained by material removal methods, indicating that its average ten point height is not greater than 6.3 micrometers.

Roughness 12.5: This represents the distance between the peaks and valleys on the surface of the part, which is 12.5 microns, and is a specific value of surface roughness.

Overall, the smaller the roughness values, the higher the machining quality and smoother the surface of the part. In practical applications, appropriate roughness values will be selected based on different usage requirements and processing conditions to meet the performance requirements of the product.