According to the mathematical formula Ra=0.2×Rz, the corresponding Ra value of roughness 63 is 12.6.

Roughness and Ra are two different surface roughness parameters. Rz and Ra have a certain relationship, not a one-to-one correspondence. The relationship between Rz and Ra can be expressed by a mathematical formula: Ra=0.2×Rz. If you substitute Rz=63, you can get the answer, and the calculated result is that the Ra value is 12.6.