Full definition
Surface roughness of the shaft contact zone for lip or mechanical seals. For rotary shaft seals (retén): Ra 0.2-0.5 μm (fine-ground). For PTFE lip seals: Ra 0.1-0.2 μm. Too smooth (<0.2 μm) prevents lubricant film formation; too rough (>0.8 μm) erodes the lip. Recommended process: helical grinding with CBN wheel or honing. Lead angle must not exceed 0.05 mm/rev.