A rail screw spike is a steel fastening connector used to secure rails to sleepers, forming a stable interface that supports rail loads, limits displacement and maintains continuous track structure. Screw spikes are indispensable for conventional ballasted track, especially on concrete and hardwood sleepers where threaded holding is required. This article explains the four main head types of screw spikes and how to choose among them.
What Are Screw Spikes
Screw spikes are threaded fasteners that are screwed into a plastic dowel, wooden sleeper or cast-in insert instead of being driven like ordinary dog spikes. Their threaded shank provides strong pull-out resistance and allows removal and re-installation during maintenance. The head type determines which driving tool is used and how much torque can be applied.
The Four Main Head Types
The four main types of screw spike heads are the Ss series sleeper screw, the square head screw spike, the hexagon head screw spike and the double-head screw spike. These types vary in shank length, diameter, thread profile and head shape to fit different sleepers and fastening systems.
| Head Type | Typical Tool | Typical Use |
|---|---|---|
| Ss series sleeper screw | Sleeper screw wrench / socket | European-style fastening on concrete sleepers |
| Square head | Square socket wrench | Traditional fastening systems |
| Hexagon head | Hex socket wrench | Easy torque application, common on many lines |
| Double head | Specialized tools | Increased fastening strength or machinery installation |
Ss Series Sleeper Screws
The Ss series sleeper screw is a specialized, commonly used type in European standard practice. It is installed into a plastic dowel in the concrete sleeper and offers consistent clamping force with reliable re-tightening. Typical specifications include M22 and M24 diameters with lengths from 130 mm to 180 mm, and weights from about 0.45 kg to 0.70 kg depending on the size.
| Type | Specification | Weight (kg) |
|---|---|---|
| Ss 1/130 | M22 x 130 | 0.451 |
| Ss 1/150 | M22 x 150 | 0.478 |
| Ss 5/150 | M24 x 150 | 0.545 |
| Ss 6/150 | M26 x 150 | 0.702 |
| Ss 8/140 | M24 x 140 | 0.528 |
| Ss 8/150 | M24 x 150 | 0.548 |
Square, Hexagon and Double-Head Types
The square head screw spike has a four-sided head and is often used in traditional fastening systems; common sizes include M22 x 145 to M22 x 195. The hexagon head screw spike has a six-sided head for easier torque application and is available in strength grades such as 4.6, 5.6, 8.8 and 10.9. The double-head screw spike, typically sized 23 x 174 mm, is designed for increased fastening strength or specific machinery installation.
Materials and Strength Grades
Screw spikes are made from carbon or alloy steels depending on the required strength. Common grades include Q235, 35#, 45# and 40Cr. Q235 suits light railway and mining tracks; 35# and 45# provide higher strength and wear resistance for main-line and heavy-duty tracks; 40Cr, a chromium alloy steel, is used for crane rails and high-load industrial tracks because of its exceptional strength, toughness and fatigue resistance. Surface treatments include plain oiled, oxide black, zinc plating, hot-dip galvanizing, Dacromet and sherardizing, selected according to the environment.
Common Misconceptions
One misconception is that head type is only a cosmetic difference; in fact, it determines tooling, torque capacity and maintenance accessibility. Another is that a higher strength grade always means a better spike; the grade must match the sleeper material to avoid damaging the dowel or cracking the sleeper. Surface treatment should also be selected for the actual climate, not simply by habit.
FAQ
Q: What are the 4 types of screw spike heads? A: Ss series sleeper screws, square head, hexagon head and double-head screw spikes.
Q: What is an Ss series sleeper screw? A: A specialized sleeper screw commonly used in European standard practice, installed into plastic dowels in concrete sleepers.
Q: What materials are screw spikes made of? A: Common grades are Q235, 35#, 45# and 40Cr alloy steel, chosen by required strength and environment.
Q: Why choose a hexagon head screw spike? A: Its six-sided head allows easier torque application with standard sockets during installation and maintenance.
Q: Do screw spikes need surface treatment? A: Yes. Zinc, hot-dip galvanizing, Dacromet or similar treatments protect the spike from corrosion in wet and aggressive environments.
