Rail Screw Spike Fastening System
The Railway Screw Spike is a precision-engineered, threaded fastener distinguished by its deep helical thread form and forged head profile, designed to secure rails to timber sleepers or concrete sleepers with pre-installed inserts through rotational installation rather than impact driving . Unlike the wedge-action dog spike that relies on wood fiber compression, the screw spike generates holding power through positive mechanical interlock-its threads engage with the sleeper material or insert to create a removable, high-strength connection that delivers pull-out resistance approximately 2.5 times greater than equivalent dog spikes .
Technical Specifications:
| Parameter | Screw Spike | Dog Spike | Lag Screw | Elastic Rail Clip |
|---|---|---|---|---|
| Fastening Principle | Threaded mechanical interlock | Fiber compression (friction) | Threaded engagement | Calibrated spring force |
| Sleeper Compatibility | Timber or concrete (with insert) | Timber only | Timber only | Concrete, steel, composite |
| Installation Method | Rotational (torque-controlled) | Impact driving | Rotational (wrench) | Press-in or clip driver |
| Pull-Out Resistance | Very high (2,500-5,000 lb) | Moderate (2,000-4,000 lb) | High | N/A (clamping force) |
| Thrust Resistance | Moderate | Good (group action) | Moderate | High |
| Installation Speed | Moderate (threaded) | Very fast (impact) | Slow (manual) | Fast |
| Removal Difficulty | Low (reverse rotation) | Moderate (puller required) | Low | Low |
Installation & Maintenance Perspective:
- Asymmetric Thread Profile: The pressure flank (load-bearing surface) is oriented at 90-100° to the spike axis, optimizing resistance to vertical uplift while the clearance flank angle facilitates installation and removal .
- Thread Pitch Optimization: Standard pitches of 6-12 mm balance installation speed against holding power-coarser threads install faster but provide less surface area engagement than finer thread variants .
- Pull-Out vs. Thrust Characteristics: While pull-out resistance exceeds dog spikes by 150%, lateral thrust resistance measures approximately 40-50% lower, necessitating closer spike spacing or supplementary fastening in high lateral load applications .
Maintenance & Operational Perspective
- Quenched and Tempered Structure: Premium spikes undergo through-hardening followed by tempering at 400-500°C, achieving core hardness of 25-35 HRC that balances wear resistance with toughness to resist impact during installation .
- Case Hardening Options: For aggressive environments, induction case hardening creates a wear-resistant surface layer (45-55 HRC) to 2-3 mm depth while maintaining ductile core properties .
- Bake Hardening Effect: Controlled cooling after forging promotes precipitation hardening that increases yield strength by 15-20% without additional alloying elements .
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