Surface roughness is a symbol used to describe the roughness of an object's surface. The following are common surface roughness symbols and their meanings:
1. Ra: Average roughness. It is the absolute value of the average deviation of the surface height of an object over a certain measured length. The smaller the Ra value, the smoother the surface.
2. Rz: Maximum peak-trough value. It is the maximum peak-trough value of the surface height of an object within a certain measured length. The smaller the Rz value, the smoother the surface.
3. Rq: rms roughness. It is the rms value of the height of the surface of an object within a certain measured length. The smaller the Rq value, the smoother the surface.
4. Rt: Maximum peak-valley height. It is the distance between the highest peak and the lowest valley on the surface of an object. The smaller the Rt value, the smoother the surface.
5. Rmax: Maximum peak height. It is the height of the highest peak on the surface of an object. The smaller the Rmax value, the smoother the surface.
These surface roughness symbols and values help engineers and manufacturers assess the quality and suitability of surfaces to determine whether they meet specific requirements and standards.