What does Ra value mean?

What Does Ra Mean? 1, Ra is the arithmetic average of the absolute values of the profile height deviations from the mean line, recorded within the evaluation length. Simply put, Ra is the average of a set of individual measurements of a surfaces peaks and valleys.

What is RA in stainless steel?

Ra or Roughness Average is the commonly used term to quantify the level of roughness of stainless steel surface. An average between the peaks and valleys of the surface is taken to calculate the roughness average of a surface. Ra is denoted by micrometers (µm) or micro-inches (µin).

What does Ra mean on a steel bar?

What Ra measures is the average distance (or height) of the peaks & valleys from the mean line. Most drawings and prints you see will have a Ra surface finish requirement called out on it. A device called a profilometer can quickly and easily measure the surface finish of a steel bar.

What does Ra surface finish look like on steel?

Actual surface profile showing the Ra surface finish of 0.164 µm (6 µin microinch) on a ground & polished steel bar. The photo of the ground & polished steel bars show what the surface finish looks like when visually looking at the surface. It looks nearly like a mirror finish, smooth to the touch if you trace your hand along the bar.

What is the Ra value of a surface?

The Ra value is defined as the average value of the departures from its centerline through a prescribed sampling length. The increasing purity requirements in the pharmaceutical and bio-technology industries require surfaces in contact with the product to have finishes that meet BPE standards.

What is the average RA?

Ra stands for Roughness Average. In past years Ra was also known as Center Line Average (CLA), or Arithmetic Average (AA), but today Ra is the most commonly used surface finish parameter in the steel industry. What Ra measures is the average distance (or height) of the peaks & valleys from the mean line.