Static Load Rating
The static load rating C0 is the static load at which the permanent (plastic) deformation of rolling element and raceway is still just small enough not to impair running. It is especially relevant under standstill, low speeds, and shock loads. The static safety factor S0 = C0 / P0 shows how far the operating point is from the damage threshold.
Definition
The static load rating C0 is defined per ISO 14728-2 (linear guides) or ISO 76 (rolling bearings) as the static load that causes a permanent deformation of 0.0001 times the rolling element diameter at the most heavily loaded contact point. Below C0 the guiding system remains functional; if C0 is exceeded, permanent indentations can form in the raceway (brinelling), leading to increased noise, vibration, and reduced service life.
Static Safety Factor S0
S0 = Static safety factor (dimensionless; guideline values depend on the application, see below)
C0 = Static load rating [N or kN]
P0 = Equivalent static load [N or kN]: highest load on the most heavily loaded bearing or carriage, including short peaks; if moments act, including the moment component
Shock and vibration are covered by a higher required S0, not by a surcharge on the load. Which S0 is sufficient depends on the application — rolling bearings and profile rail guides have different guideline values.
Guideline values for S0: profile rail guides
| Operating condition | S0 |
|---|---|
| All loads known, smooth running without shock | 3–5 |
| Normal design: loads partly estimated or accuracy of the mounting surfaces not assured; moderate shock and vibration (including from acceleration and braking) | 5–8 |
| High dynamic loading or vibration at standstill, heavy shock, contamination | 8–12 |
| Hanging (overhead) arrangement or high hazard potential — up to 20 with uncertain loads and few carriages; provide fall protection | from 12 |
Notes on the guideline values
The table is the same as in our “Linear Guide Sizing” calculator. P0 (F in the calculator) is the highest load on the most heavily loaded carriage, including short peaks. If moments act, use the equivalent static load (force plus moment component according to the manufacturer catalogue). The guideline values are conservative and follow European manufacturers. Other manufacturers, e.g. from Japan and Taiwan, specify lower minimum values with their own calculation methods (correction factors, separate moment check), roughly 1–3 without and 2–5 with shock. The calculation method and guideline value of the manufacturer actually used are binding.
Rolling bearings (static load rating per ISO 76) have their own guideline values from the bearing manufacturers: depending on the requirements for smooth running and on shock, usually S0 ≈ 1–3, lower for modest requirements, higher for heavy shock. These values cannot be transferred to profile rail guides.
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