The relationship between surface finish and roughness

Surface finish is the old standard for surface roughness;

Their correspondence:

Surface finish grade 14 = RA

Surface finish grade 13 = ra

Surface finish grade 12 = ra

Surface finish grade 11 = ra

Surface finish grade 10 = RA

Surface finish grade 9 = ra

Surface Finish Grade 8 = RA

Surface finish grade 7 = ra

Surface finish grade 6 = ra

Surface Finish Grade 5 = Ra

Surface finish grade 4 = ra

Surface Finish Grade 3 = RA 25

Surface finish grade 2 = RA 50

Surface finish grade 1 = RA 100

The above surface roughness units are m, i.e. microns = 10 -6 meters.

Surface finish is the old standard name, and later changed to surface roughness. The micron industry is called

1 mm = 10 filaments 1 filament = 10 m

Microns (m).

1μm=1×10^(-6)m

All I know is that the roughness is smaller, the higher the finish. It's obvious.

Finish.

Surface roughness. ra

RZ surface finish.

Surface roughness. rarz

In fact, the new standard replaces the old standard, and the specific comparison is shown in the table.

First, the reference is different.

1. Roughness: the unevenness of the small spacing and small peaks and valleys on the machined surface. The distance (wave distance) between two peaks or troughs is small (less than 1 mm), and it is a microgeometric error. The smaller the surface roughness, the smoother the surface.

2. Finish: The surface finish is the degree of flatness of the processed surface from the perspective of human vision.

Second, the measurement method is different.

1. Roughness: A method to determine the value of the measured surface roughness by comparing the measured surface with the roughness sample marked with a certain value. Methods that can be used for comparison: use visual inspection when RA> use a magnifying glass, and use a comparative microscope when RA.

2. Finish: The shape error of the measured surface is displayed in an interference fringe pattern by using the principle of optical code starvation interference (see flat crystal and laser length measurement technology), and the microscopic part of these interference fringes is magnified and measured by using a microscope with high magnification and high grinding die (up to 500 times).

Third, the role is different.

1. Roughness: The surface roughness value is small, which will improve the quality of the fit, reduce wear and tear, and prolong the service life of the parts, but the processing cost of the parts will increase.

2. Finish: It will have different degrees of influence on the coating of parts, thermal conductivity and contact resistance, reflection ability and radiation performance, blind resistance of liquid and gas flow, and the flow of current on the surface of the conductor.

Surface roughness refers to the unevenness of the machined surface with small spacing and small peaks.

Surface roughness is generally formed by the machining method used and other factors, such as the friction between the tool and the surface of the part during machining, the plastic deformation of the surface metal layer when the chips are separated, and the high-frequency vibration in the process system. Due to the different processing methods and workpiece materials, the depth, density, shape and texture of the traces left on the machined surface are different.

The surface roughness is closely related to the mating properties, wear resistance, fatigue strength, contact stiffness, vibration and noise of mechanical parts, and has an important impact on the service life and reliability of mechanical products. In general, RA is used for labeling.

Effect of surface roughness on parts:

It affects the wear resistance of the part, the stability of the mating properties, the fatigue strength of the part, the inability to fit tightly between the surfaces of the parts, the contact stiffness of the parts, and the measurement accuracy of the parts with bright and sensitive segments.

In addition, surface roughness has varying degrees of influence on the coating of parts, thermal conductivity and contact resistance, reflectivity and radiation properties, resistance to the flow of liquids and gases, and the flow of current on the surface of the conductor. <>