Surface Roughness (Ra) Selection: A Practical Guide

Surface finish affects aesthetics, friction, and corrosion resistance, but lower Ra values aren't always better:

Avoid Over-Polishing

Mirror finishes (Ra<0.4μm) require expensive manual polishing. Most industrial parts perform well at Ra1.6-3.2μm.

Consider Texture Direction

Critical for sliding surfaces - specify lay orientation relative to motion.

Account for Post-Processing

Blasting/coating alters surface texture - include finishing allowances.

General Guidelines

Non-contact surfaces: Ra6.3-12.5μm

Standard fits: Ra1.6-3.2μm

Precision bearings: Ra0.4-0.8μm