What is fish plate and fish bolt in railway?

In railway engineering, fish plates and fish bolts are core components of a traditional rail joint system, used to connect two adjacent rails end-to-end and maintain track continuity.

What Is a Fish Plate in Railway?

A fish plate (also called a joint bar) is a pair of metal plates fixed to both sides of the rail web at the rail joint. Its primary function is to align and hold two rail ends together, ensuring continuity in the vertical, lateral, and longitudinal directions.

Structurally, fish plates are designed to match the rail profile. The inner face usually has a machined contour that fits the rail web and foot, while bolt holes are precisely positioned to ensure correct load transfer. Most fish plates are manufactured from high-strength carbon steel or alloy steel, providing sufficient fatigue resistance under repeated wheel loads.

From a functional perspective, fish plates:

• Maintain correct rail alignment at joints

• Transfer wheel loads smoothly across the joint

• Reduce impact forces and rail end batter

• Allow limited rail expansion and contraction

Fish plates are still widely used in conventional jointed tracks, industrial railways, mining lines, and temporary or auxiliary tracks, even though modern mainlines increasingly adopt continuous welded rail (CWR).

Types of Fishplates

Railway fishplates can be classified according to rail application, functional performance, size compatibility, structural form, and manufacturing method, ensuring reliable rail joint performance under different track conditions.

According to rail weight and usage, fishplates are mainly divided into light rail fishplates, heavy rail fishplates, and crane rail fishplates. Light rail fishplates are used for rails ranging from 8kg/m to 30kg/m and are sometimes referred to as flat joint bars. Heavy rail fishplates are designed for rails of 38kg/m and above, commonly applied on mainline railways and industrial tracks. For crane rail systems, oblique joint fishplates are specially produced for QU70, QU80, QU100, and QU120 crane rails to withstand high wheel loads and frequent impact.

From a functional perspective, fishplates include ordinary fishplates and insulated fishplates. Insulated fishplates are made from high-strength composite insulating materials and offer corrosion resistance, UV resistance, non-conductivity, and non-magnetic properties. As thermosetting products, they cannot be reprocessed after molding, ensuring stable performance and reduced theft risk. These fishplates are widely used in track sections requiring electrical insulation.

In terms of size compatibility, fishplates must strictly match the corresponding rail sections. Common models cover light rails such as 8kg, 9kg, 12kg, 15kg, 18kg, 22kg, 24kg, and 30kg, as well as heavy rails including 38kg, 43kg, 50kg, 60kg, and 75kg. Fishplates are also available for international standards such as S49, UIC54, UIC60, BS75R, BS80A, BS90A, BS95RBH, BS100A, and BS113A, in both standard and insulated types.

Types	Standard	Material	Holes
UIC54 Fishplate	UIC 864	Grade 700	4 holes or 6 holes
UIC60 Fishplate	UIC 864	Grade 700	4 holes or 6 holes
115RE Rail Fishplate	AREMA	Grade 55#	4 holes or 6 holes
132RE Rail Fishplate	AREMA	Grade 55#	4 holes or 6 holes
BS80A fishplate	BS 47-1	European Grade 700	4 holes
BS90A fishplate	BS 47-1	European Grade 700	4 holes
BS100A fishplate	BS 47-1	European Grade 700	4 holes
31kg fishplate	AS 1085.2-2002	AS 1442 or AS 1448	4 holes or 6 holes
41kg& 47kg fishplate	AS 1085.2-2002	AS 1442 or AS 1448	4 holes or 6 holes
43 kg, 50kg, 60kg, 75kg fishplate	TB/T 2345-2008	B7	4 holes or 6 holes
S49 Fishplate	DIN5902:1995	Grade 700	4 holes or 6 holes

Structurally, metal fishplates are typically produced with four-hole or six-hole designs to meet different rail profiles and load requirements. Depending on material and process, fishplates can be manufactured by casting, forging, rolling, pressing, or injection molding, using medium- or high-carbon steel or composite materials to ensure adequate strength, toughness, and fatigue resistance.

What Is a Fish Bolt in Railway?

A fish bolt is a high-strength fastener used to clamp fish plates tightly to the rail web. Fish bolts pass through the aligned holes in the fish plates and rail, working together with nuts and washers to generate the required clamping force.

Fish bolts are typically manufactured from medium-carbon steel or alloy steel, with common mechanical grades such as 4.6, 5.6, or 8.8, depending on load requirements. Surface treatments may include black oxide, zinc plating, hot-dip galvanizing, or Dacromet, improving corrosion resistance in harsh environments.

Fish Bolt Specifications:

Railway Fish Bolt Technical parameters：

Grade	4.6	5.6	8.8	10.9
Material	Q235	35#	45#	40Cr
Mechanical properties	Tensile strength: ≥400Mpa	Tensile strength: ≥500Mpa	Tensile strength:≥800Mpa	Tensile strength: ≥1000Mpa
	Yield strength:≥240Mpa	Yield strength:≥300Mpa	Yield strength:≥640Mpa	Yield strength:≥900Mpa
	Elongation:≥22%	Elongation:≥20%	Elongation:≥12%	Elongation:≥9%
	Cold bending: 90 degree without crac	Cold bending: 90 degree without crac	Cold bending: 90 degree without crac	Cold bending: 90 degree without crac
Surface	plain (oiled), Oxide black, Zinc, HDG, wax, bitumen, Dacromet, Sherardizing
Standard refers	UIC864-2

The main functions of fish bolts include:

• Providing sufficient clamping force to prevent joint loosening

• Ensuring effective load transfer between rails

• Maintaining long-term joint stability under vibration and impact

• Allowing controlled joint movement caused by temperature changes

Correct bolt torque is critical: insufficient torque leads to joint loosening, while excessive torque may cause bolt failure or rail web damage.

Relationship Between Fish Plates and Fish Bolts

Fish plates and fish bolts function as a single integrated joint system. Fish plates provide structural alignment and load distribution, while fish bolts deliver the clamping force required to lock the assembly together. Without fish bolts, fish plates cannot perform their mechanical role; without fish plates, fish bolts have no structural element to secure.

In practical railway applications, they are always selected and installed as a matched system, compatible with the specific rail section, loading conditions, and applicable railway standards.

GNEE RAIL offers different kinds of railway fasteners to meet client’s requirements, such as Elastic Rail Clip and Clamp, Rail Screw Spike, Plastic Dowel, High Tensile Track Bolt with Nut, Rail Base(Tie) Plate, Rail Fish Plate, Railway Shoulder(Insert), Fish Bolt, Railroad Rubber and EVA Pad, etc. Samples and drawings provided by customer, we will manufacture qualified products accordingly.