What does the number of drilling angles mean?

The maximum number of protrusions or depressions per square centimeter on the surface of an object. Ra or Rz value, where Ra value is average roughness and Rz value is maximum peak-to-peak roughness. The smaller these values, the smoother the surface of the object, and the more suitable for industrial applications requiring high precision. In machining and manufacturing, the number of drilling angles is a very important quality index, and it is also an important parameter to measure machining accuracy and surface quality.