Choose Surface Finish Based on Function, Not Just Looks

Surface finish affects part performance, not just appearance. A common mistake is specifying a fine finish everywhere, which adds cost without benefit. Instead, match the finish to the function.

For sliding surfaces, a smoother finish reduces friction and wear. For pressure seals, low Ra values help prevent leaks. But rough finishes can retain lubricant or improve adhesion for coatings. Consider the operating environment and contact conditions.

Manufacturing cost rises significantly with tighter finishes. Use rougher finishes for non-critical areas like mounting faces or internal cavities. Typically, a 3.2 µm Ra is adequate for many general applications, while 0.8 µm or finer is for precision fits.

When specifying, use Ra or Rz parameters and note the lay direction if orientation matters. Avoid over-specifying; a 0.4 µm finish on a bracket is unnecessary. Always consult your machinist early to balance function, cost, and capability.

#VacuumCasting# #ToolMaking# #Microfabrication#