Grinding Terms Glossary

The velocity of the grinding wheel periphery in feet per minute. The primary parameter for setting grinding speed. SFM = RPM × Diameter(in) × π ÷ 12.

Metric equivalent of SFM. Used in metric shops. MPS = RPM × Diameter(mm) × π ÷ 60,000.

How many times the spindle rotates per minute. Does not directly describe cutting speed — must convert to SFM using wheel diameter.

The arithmetic mean of the absolute values of the profile height deviations. The most common surface finish specification. Lower = smoother.

The sum of the height of the highest peak and the depth of the deepest valley over a sampling length. Often specified alongside Ra for bearing and sealing surfaces.

Volume of material removed per unit time, typically in cubic inches per minute (in³/min) or mm³/s. MRR = Width × Depth of Cut × Table Feed Rate.

The length of the arc where the grinding wheel contacts the workpiece. Affects heat generation and deflections. Longer contact = more heat.

A grinding operation where the wheel depth of cut is large (up to 0.5 inch) and table feed is slow, producing a large contact area. Used for profile and slot grinding.

The process of restoring a grinding wheel's cutting sharpness by removing loaded or glazed surface layers. Done with a dressing stick, rotary dresser, or diamond dresser.

When the wheel surface becomes shiny and dull from loaded abrasive grains. Causes poor cutting action, heat buildup, and surface burns. Sign that dressing is needed.

When chips and swarf fill the spaces between abrasive grains, preventing cutting action. Common with soft, gummy materials like aluminum. Use appropriate wheel grit and dressing.

The velocity of the outermost edge of the wheel. Numerically identical to SFM (imperial) or MPS (metric). A 6-inch wheel at 3000 RPM = 4,712 surface feet per minute.

The speed at which the workpiece table moves under the grinding wheel, typically in inches per minute (ipm) or mm/min. Affects Ra and MRR directly.

The amount of material removed per pass from the workpiece surface, typically measured in thousandths of an inch (mils) or microns. Affects MRR and heat generation.

Discoloration or metallurgical damage to the workpiece surface caused by excessive heat in the grinding zone. Appears as blue, purple, or black discoloration. Can compromise part strength.

The period at the end of a grinding pass where the wheel continues running without further depth of cut, allowing vibrations and deflections to settle for final sizing and surface finish.