Y=Roughness, S=Lay, V=Waviness

In considering the concept of surface finish, we will disregard any sporadic surface defects, which have mechanical or metallurgical causes.  Instead, we will concentrate on the minute, evenly distributed irregularities in the surface layer, which are characteristic of the different means of production and finishing of the steel product. In terms of strict definition, the concept "surface finish" can be said to describe the deviation from the ideal flat surface. This deviation is normally expressed in terms such as roughness, lay and waviness, which in turn may be defined as:

• Roughness represents the size of the finely distributed surface pattern deviations from the smooth surface.
• Lay represents the dominant direction of the surface pattern, such as grinding scores.
• Waviness represents deviations, which are relatively far apart.

Of these, waviness is the most difficult to detect with the naked eye.