In rail terminology, a fishplate (also known as a splice bar or joint bar) is a metal bar bolted to the ends of two rails to join them. It grips the rail head and foot and draws the rail ends together, restoring alignment and reducing relative movement. Fishplates are a simple, widely used component on jointed track where rails are laid in discrete lengths rather than as a continuous welded rail.
Design and materials
Typical fishplates are made from steel and are shaped to match the rail profile so their inner faces sit against the web or base of the rail. The outer edges are often tapered so the plate wedges against the rail when bolted. A pair of matching plates—one on each side of the rail web—are fastened with bolts that pass through drilled holes in the rail ends. Variants include insulated joint bars used to maintain electrical separation for track circuits and heavier splice bars employed where increased strength is required.
Functions and common uses
- Alignment: keeps two rail ends in correct vertical and horizontal position.
- Strength: shares bending loads at the joint and reduces stress concentration.
- Electrical continuity: helps provide a return path for traction current (unless insulated).
- Maintenance: allows easier rail replacement and adjustment than welded joints.
Railway operators monitor fishplates because loose or fractured plates and bolts are a common source of joint failures. In cold climates rail expansion and gaps can alter joint behavior, so bolt torque, plate wear and corrosion are regular maintenance concerns.
History and alternatives
The term "fishplate" comes from the nautical word "fish", a plank used to reinforce a mast; the rail engineering name reflects the reinforcing role of the bar. Fishplates were essential to early railways built from short lengths of rail. Over time, continuous welded rail reduced the number of bolted joints on main lines, improving ride quality and reducing maintenance. Nevertheless, fishplates remain important on sidings, yard tracks, lightly used lines and at insulated joints.
In model railroading, tiny slip-on fishplates made of copper or nickel silver are common; they both align the rail ends and maintain electrical continuity between sections. Modern track systems may instead use fishplates with insulating material to separate track circuits or use bonding straps that bypass the joint electrically while preserving mechanical stiffness.
Notable distinctions include insulated joint bars versus conductive splice bars, and bolted fishplates versus welded joints. Despite being a small component, the fishplate plays a key role in track integrity, signaling behavior and the practical maintenance of railway networks.