A rail fish plate is a joint stabilization component that keeps rail ends in the correct relative position, maintaining track geometry and operational reliability in jointed rail systems. Fish plates, also called splice bars or joint bars, are steel bars bolted to the ends of rails to connect them, ensuring structural continuity, alignment and stability. They transfer vertical and lateral loads between rails, prevent rail separation and reduce vibration to improve safety and comfort.
Core Functions of Fish Plates
Connecting rails: joining two rail ends securely with bolts
Maintaining alignment: keeping horizontal and vertical alignment of the rail surface and gauge face
Load distribution: transferring the weight of trains from one rail to the next and reducing stress at the joint
Structural support: providing stiffness to the rail joint and reducing deflection under heavy loads
Frame reinforcement: in structural engineering, strengthening or repairing joints in metal frames by overlapping connecting pieces
Safety and Maintenance Roles
Fish plates are used in regular rail joints, in insulated joints for signaling circuits and in the emergency repair of broken rails. Insulated joint bars break the electrical continuity of the rail so that track circuits can detect train position, while emergency joint bars allow a damaged rail section to be clamped and returned to service quickly.
Fishplate Sizes and Configurations
Rail fishplates typically measure between 600 mm and 1000 mm in length with four or six bolt holes and are engineered to match the height and profile of the rail. They are available in weights from about 10 kg to over 25 kg, tailored to rail types such as UIC60, 115RE and 132-136RE.
| Standard | Rail Type | Configuration | Weight |
|---|---|---|---|
| AREMA 2007 | 115RE | 4 hole, 24 inch | 17.04 kg |
| AREMA 2007 | 115RE | 6 hole, 36 inch | 25.56 kg |
| AREMA 2007 | 132-136RE | 4 hole, 24 inch | 17.75 kg |
| AREMA 2007 | 132-136RE | 6 hole, 36 inch | 26.63 kg |
| UIC 864 | UIC60 | 4 hole, 630 mm, dia 26 mm | 18.07 kg |
| UIC 864 | UIC60 | 4 hole, 600 mm, dia 28 mm | 17.47 kg |
| UIC 864 | UIC54 | 4 hole | 14.34 kg |
| UIC 864 | UIC54 | 6 hole, 800 mm | 19.94 kg |
| BS 47-1 | BS75R | 4 hole | 6.56 kg |
| BS 47-1 | BS100A | 4 hole | not given |
| AS | 50 kg | 4 hole | 14.3 kg |
| AS | 50 kg | 6 hole | 19.5 kg |
| S49 | S49 | 4 hole | 9.71 kg |
Materials and Standards
Fish plates are commonly made of high-strength carbon steel such as grade 45 or grade 55 steel. Steel chemistry is controlled for strength and weldability, with carbon content typically between 0.42 and 0.70 percent, manganese between 0.50 and 0.80 percent and silicon between 0.17 and 0.37 percent, with phosphorus and sulfur limited to 0.035 percent maximum. Finished bars are checked for dimensional accuracy, bolt hole alignment and surface quality.
Selection Notes
Match the fishplate length, hole count and bar profile to the rail section and the joint standard of the project. Confirm the bolt diameter and the required surface treatment before ordering, and verify compatibility when the joint is intended for insulated signaling circuits.
Frequently Asked Questions
What is the main purpose of a fish plate? It connects two rail ends and transfers train loads between them while keeping the rails aligned and stable.
How long are fish plates? Typical lengths are 600 mm to 1000 mm, with four or six bolt holes.
Can fish plates be used for signaling? Yes, insulated fishplates break electrical continuity so track circuits can detect train position.
What steel is used to make fish plates? High-strength carbon steel such as grade 45 or grade 55 is commonly used.
How heavy is a fishplate? Weight depends on rail size and length, ranging from about 6 kg for light sections to over 26 kg for heavy AREMA sections.
