Which unit is used to express surface roughness in the thermally cut surface standard?

Which unit is used to express surface roughness in the thermally cut surface standard?

• A. Inches
• B. Millimeters
• C. Micrometers
• D. Nanometers

Answer: (C)

Surface roughness of thermally cut metal is quantified in micrometers because the texture deviations are small and micrometers (μm) provide the practical resolution inspectors use. The common measure, Ra, is given in μm, which lines up with how profilometers and surface gauges assess and compare finish quality after cutting processes like oxy-fuel or plasma. Using micrometers keeps the numbers manageable and meaningful for accept/reject criteria; inches or millimeters would be too coarse to distinguish the finer roughness variations, and nanometers would imply an unrealistically smooth surface for typical thermally cut edges. Therefore, micrometers is the appropriate unit.

Surface roughness of thermally cut metal is quantified in micrometers because the texture deviations are small and micrometers (μm) provide the practical resolution inspectors use. The common measure, Ra, is given in μm, which lines up with how profilometers and surface gauges assess and compare finish quality after cutting processes like oxy-fuel or plasma. Using micrometers keeps the numbers manageable and meaningful for accept/reject criteria; inches or millimeters would be too coarse to distinguish the finer roughness variations, and nanometers would imply an unrealistically smooth surface for typical thermally cut edges. Therefore, micrometers is the appropriate unit.