THK LMK20 Linear Bushing
The LMK20 is a square-flanged linear bushing from THK's LMK series, designed for smooth, low-friction linear motion. Its compact square-flange design lowers the center height compared to round-flange types, enabling space-efficient machine integration. Ideal for precision machinery, automation equipment, and instrumentation requiring stable linear guidance and easy mounting.
The LMK20 is a square-flanged linear bushing from THK's LMK series, designed for smooth, low-friction linear motion. Its compact square-flange design lowers the center height compared to round-flange types, enabling space-efficient machine integration. Ideal for precision machinery, automation equipment, and instrumentation requiring stable linear guidance and easy mounting.
Official Specifications
| Parameter | Value | Unit |
|---|---|---|
| Inscribed Bore Diameter (dr) | 20 | mm |
| Bore Diameter Tolerance | 0 / –0.012 | mm |
| Outer Diameter (D) | 32 | mm |
| Outer Diameter Tolerance | 0 / –0.019 | mm |
| Overall Length (L) | 42 | mm |
| Length Tolerance | ±0.3 | mm |
| Flange Diameter (D₁) | 48 | mm |
| Flange Diameter Tolerance | 0 / –0.2 | mm |
| Number of Ball Rows | 5 | — |
| Basic Dynamic Load Rating (C) | 863 | N |
| Basic Static Load Rating (C₀) | 1370 | N |
| Mass | 100 | g |
| PCD (Mounting Hole Circle) | 37 | mm |
| Mounting Hole (d₁×d₂×h) | 5.5×9.2×5.4 | mm |
| Max Flange Perpendicularity | 15 | μm |
| Max Eccentricity | 15 | μm |
| Radial Clearance | Standard (–8 μm) | μm |
| Retainer Material | Synthetic Resin | — |
| Outer Sleeve Material | High-carbon Chromium Bearing Steel (SUJ2) | — |
| Ball Material | Hardened Steel | — |
| Operating Temperature Range | –10°C to +80°C | °C |
| Standard Lubrication | Pre-lubricated with anti-rust oil | — |
| Seal Type (UU Option) | Double contact seals (both ends) | — |
Key Features
- Square Flange Design: Four-sided flattened flange for low-profile installation and compact assembly.
- High Precision: Strict dimensional tolerances ensure ultra-smooth linear motion and minimal clearance.
- 5-Row Ball Configuration: Balanced radial load capacity and stable operation under moderate to high loads.
- Resin Retainer: Lightweight, low-noise ball circulation with consistent performance.
- Easy Installation: Direct bolting via square flange without additional fixtures; interchangeable with standard shafts.
Official Notes
- For linear motion only; not suitable for pure rotational or moment loads.
- LMK20UU variant includes double UU seals for enhanced dust protection and lubrication retention.
- Recommended shaft: Surface hardness ≥58 HRC, surface roughness Ra ≤0.4 μm.
- Operating temperature must not exceed 80°C to prevent retainer deformation.
- Re-lubricate with lithium-based grease periodically for extended service life.
