THK Linear Ball Bearing ST8
The THK ST8 is a compact, lightweight linear/rotary ball bearing designed for light-load applications requiring both linear and rotational motion, or a combination of both. Engineered with a precision ball cage assembly, it delivers exceptionally low friction (μ=0.0006~0.0012) and smooth operation. Its slim, thin-walled profile saves space and weight, ideal for compact precision mechanisms.
The THK ST8 is a compact, lightweight linear/rotary ball bearing designed for light-load applications requiring both linear and rotational motion, or a combination of both. Engineered with a precision ball cage assembly, it delivers exceptionally low friction (μ=0.0006~0.0012) and smooth operation. Its slim, thin-walled profile saves space and weight, ideal for compact precision mechanisms. This model supports an extended stroke and is typically used in instruments, optical devices, and small automated equipment.
Official Specifications
| Parameter | Value | Unit |
|---|---|---|
| Inscribed Bore Diameter (dr) | 8 | mm |
| Bore Diameter Tolerance | +0.022 / 0 | mm |
| Outer Diameter (D) | 15 | mm |
| Outer Diameter Tolerance | +0.013 / -0.008 | mm |
| Overall Length (L) | 24 | mm |
| Maximum Stroke (S) | 14 | mm |
| Basic Dynamic Load Rating (C) | 9.8 | N |
| Basic Static Load Rating (C₀) | 2.7 | N |
| Mass | 5.5 | g |
| Number of Balls | 18 | — |
| Ball Material | High-Carbon Chromium Steel (SUJ2) | — |
| Outer Cylinder Material | High-Carbon Chromium Steel (SUJ2) | — |
| Cage Material | Light Alloy | — |
| Operating Temperature | -15°C to +80°C | °C |
| Standard Lubrication | Pre-lubricated with grease | — |
| Seal Type | None (Open Type) | — |
| Type | Light Load, Long Stroke | — |
Key Features
- Dual-Motion Capability: Uniquely designed to permit linear, rotary, and combined linear-rotary movement with minimal friction.
- Ultra-Low Friction: Point contact between balls and raceways, plus separated ball retention, achieves an extremely low friction coefficient.
- Long Stroke: Maximum stroke (14 mm) is effectively double the travel range of the internal ball cage.
- Compact & Lightweight: Slim outer tube construction minimizes outer diameter and weight, perfect for space-constrained designs.
- High Precision: Precision-machined cage and hardened components ensure stable, accurate, and quiet motion.
- Light Alloy Cage: High rigidity, low weight, and excellent durability for consistent long-term performance.
Official Applications
- Optical Measuring Instruments & Precision Spindles
- Printing Machine Ink Rollers
- Textile Machinery & Strain Measuring Equipment
- Copiers & Office Automation Equipment
- Small Precision Actuators & Portable Devices
Variant Information
- ST8UU: Same dimensions as ST8, equipped with double lip seals for dust protection.
- ST8B: Medium-load, shorter-stroke version with double the load rating.
