The aluminum alloy piston produced by our factory has different surface roughness Rα values. It is turned, rolled, and ground, and requires different surface roughness comparison samples. According to the requirements of the roughness grade of each part of the piston, I chose the piston of the same material. After the special processing, I removed the small square with a length of 30mm and a width of 25mm at the required part, including top turning and head turning and (? ) Grinding and other sample blocks, two parts for each part are easy to determine. The small square is taken to the surface roughness measuring instrument for verification, and the Rα value is marked. Such a simple and practical sample is ready.