How to measure surface roughness of metal?
There are numerous parameters to measure a profile’s roughness, of which the value Ra is the most common. Ra measures within a certain sampling length the arithmetic average of the peaks and valleys of the metal surface, including the deviations from the mean line. Measuring surface roughness is done with a profilometer or laser scanner. The greater the deviations, the rougher the surface and if the Ra is small, the surface is smooth. The Ra will be calculated in micrometers (µm) or microinches (µin.). References: Surface roughness
How to get the metal plate with the required roughness Ra?
We use multiple sets of sanding belts to complete it, starting from 80# and ending with 1000#.
Please refer to the following data:
| Surface finish level | Surface roughness Ra | Surface roughness Rz | Belt grit |
| Surface finish level 1 | 100 | 200
|
|
| Surface finish level 2 | 50 | 100 |
|
| Surface finish level 3 | 25 | 50 |
|
| Surface finish level 4 | 12.5 | 25 |
|
| Surface finish level 5 | 6.3 | 12.5 |
|
| Surface finish level 6 | 3.2 | 6.3 | 80# |
| Surface finish level 7 | 1.6 | 6.3 | 120# |
| Surface finish level 8 | 0.8 | 3.2 | 240# |
| Surface finish level 9 | 0.4 | 1.6 | 400# |
| Surface finish level 10 | 0.2 | 0.8 | 600# |
| Surface finish level 11 | 0.1 | 0.4 | 1000# |
