THK LM20UU Linear Ball Bushing
The LM20UU is a standard closed‑type linear ball bushing from THK's LM‑UU series. It features a precision‑ground cylindrical outer sleeve, resin retainer, and UU double‑lip dust seals, delivering smooth, low‑friction linear motion with stable radial load capacity. It is widely used in automation equipment, precision machinery, and general linear guidance systems requiring high accuracy and reliability.
The LM20UU is a standard closed‑type linear ball bushing from THK’s LM‑UU series. It features a precision‑ground cylindrical outer sleeve, resin retainer, and UU double‑lip dust seals, delivering smooth, low‑friction linear motion with stable radial load capacity. It is widely used in automation equipment, precision machinery, and general linear guidance systems requiring high accuracy and reliability.
Official Specifications
| Parameter | Value | Unit |
|---|---|---|
| Inner bore diameter (dr) | 20 | mm |
| Outer diameter (D) | 32 | mm |
| Overall length (L) | 42 | mm |
| Number of ball rows | 5 | — |
| Basic dynamic load rating (C) | 980 | N |
| Basic static load rating (C₀) | 1,570 | N |
| Mass | 87 | g |
| Bore diameter tolerance (High grade) | 0 / –0.007 | mm |
| Outer diameter tolerance (High grade) | 0 / –0.016 | mm |
| Length tolerance | ±0.20 | mm |
| Max eccentricity | 15 | μm |
| Radial clearance (High grade) | –6 | μm |
| Retainer material | Resin | — |
| Outer sleeve material | High‑carbon chromium bearing steel (SUJ2) | — |
| Ball material | Hardened steel | — |
| Operating temperature range | –15°C to +80°C | °C |
| Seal type | UU (double‑lip seals) | — |
| Lubrication | Pre‑lubricated with rust‑preventive oil; lithium‑based grease recommended | — |
Key Features
- Closed‑type design: Full cylindrical structure for stable radial load support and consistent performance.
- UU double‑lip seals: Effective dust and moisture protection, extending service life in harsh environments.
- Resin retainer: Lightweight, low‑noise operation with stable ball guidance.
- High precision: Strict dimensional tolerances ensure smooth motion and interchangeability.
- Standard dimensions: Fully compatible with THK LM‑series shafts and metric linear motion systems.
Official Notes
- Designed exclusively for linear motion; not for pure rotational or moment loads. Use multiple bushings on a single shaft to resist moment loads.
- Recommended lubrication: THK AFB‑L grease or equivalent lithium‑based grease.
- Shaft requirements: Surface hardness ≥58 HRC, surface roughness Ra ≤0.4 μm.
- Operating temperature must not exceed 80°C to prevent resin retainer degradation.
