Surface roughness measurement in our laboratory and workshop
Stainless steel grinded grain 180 or grained 320 must have this surface value is definitely not true! This statement and definition is absolutely wrong!
We perceive surfaces with our natural senses. The comparison rough and finely ground based on personal subjective perceptions. Whether a surface is rough or fine, each person feels differently. Our surface measurements and evaluations are processed according to DIN EN ISO 4288: 1998, as long as they are defined and requested as such in the order.
Surface values Ra and Rz in comparison
The surface comparison on a 40x40x2 square tube 1.4301 with Ra, Rz, Rq value and graphical representation. The sequence of images is arranged in such a way that the graph is shown first, then the Ra value, followed by the Rq value in the next line and finally the Rz value directly below the Ra value. The measured Ra value of 1.009µ in the top row of images is only 0.027µ finer than the second row of images. However, the Rz value is 1.157µ lower than in the second row. This clearly shows that a lower Ra value does not always result in a better Rz value
Marginal differences in the surface
Here is the same square tube 40x40x2 from the same series of polishing as the pictures above. The Ra values differ slightly although it is the same batch and the same machine parameters at almost the same longitudinal point of the tube.
matchbox friction area measurement
The wellknown surface of a matchbox shows a lot of different measurement values on the same stripe. So it`s quite difficult to make a consist statement about surfaces which are seen and the difference when they are felt and measured.