Key Takeaways:
Hydrostatic bearings routinely achieve radial runout at or below 0.1 μm (high-end designs reach 0.02 μm). The non-contact oil film removes the runout sources that limit rolling bearings.
Runout Defines Precision
Radial runout—the deviation of the rotating axis from a perfect circle—directly limits achievable surface finish and geometric accuracy. Rolling bearings are hard-pressed to reach sub-micron runout because of their discrete contact elements.

How Hydrostatic Hits 0.1 μm
A hydrostatic bearing floats the shaft on a continuous pressurized oil film, eliminating the discrete contact points of rolling elements. With proper cavity flatness (≤0.5 μm) and clean, temperature-stable oil, radial runout reaches ≤0.1 μm, and high-end designs achieve 0.02 μm. Marusaku rotary tables demonstrate this with ±0.001 mm rotary positioning.
Why It Holds
Because there is no contact wear, the runout does not degrade over time—accuracy is built into the film, not into mechanical parts that wear out.