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Fish bolts, also known as rail bolts or fishtail bolts, are a specialized fasteners used in railway construction to join two fish plates that connect two rail tracks. These bolts, made from low or medium carbon steel, have unique head shapes and feature spring washers and nuts to securely fasten the rail joints. They are designed to withstand the significant stress of railway operations, improving ride quality and safety by ensuring a continuous and robust connection between rails.
Connecting rail tracks: A fishplate is placed on either side of a rail joint (the point where two rail ends meet), and fish bolts are inserted through holes in both the plates and the rail web.
Distributing stress: When the nuts are tightened, the fish bolts firmly hold the plates against the rails. This distributes the stress across the joint, preventing misalignment and premature wear of the rail ends.
Accommodating movement: The bolt holes are slightly larger than the bolts themselves. This allows the rails to expand and contract with temperature changes without putting too much strain on the joint.
Ensuring stability: Used with nuts and spring washers, fish bolts ensure a tight, secure connection that withstands the dynamic stresses and vibrations from passing trains.
There are a few different types and grades of fish bolts, including:
Common fish bolts: Made from standard steel, they are used for many general applications.
High-strength fish bolts: Made from stronger, high-carbon alloy steel, these are often used for permanent connections, such as on bridges or high-speed rail lines.
Insulated fish bolts: Used with insulated fishplates, these prevent electrical currents from passing between rail sections, which is important for track signaling systems.
A fish bolt is fundamentally different from a standard bolt in its specialized design and purpose, as it is engineered to withstand the extreme dynamic stresses and vibrations found in railway applications. A standard bolt is a general-purpose fastener designed for various uses in construction and machinery.
Key Differences Between Fish Bolts And Standard Bolts
A fish bolt is fundamentally different from a standard bolt in its specialized design and purpose, as it is engineered to withstand the extreme dynamic stresses and vibrations found in railway applications. A standard bolt is a general-purpose fastener designed for various uses in construction and machinery.
Fish bolts, also known as track bolts, are available in several head types, each designed to meet specific railway and fastening standards. The head and neck design are crucial for preventing the bolt from rotating when the nut is tightened, ensuring a secure and reliable connection.
Common head types for fish bolts
Oval Neck Fish Bolt: These are among the most common types. The neck has an elongated oval or elliptical shape that fits into a correspondingly shaped hole in the fishplate, preventing the bolt from turning when the nut is fastened.
Cup Head Oval Neck Fish Bolt: This variant features a rounded, cup-shaped head in addition to the oval neck. It provides a smooth bearing surface that reduces stress concentration on the fishplate and minimizes the risk of snagging.
Button Head Oval Neck Track Bolt: Similar to the cup head, this bolt has a rounded, low-profile, button-shaped head. The sleek design is ideal for applications where minimizing obstructions and creating a flush surface are important.
Square Head Track Bolt: These bolts have a square head and a square neck. The square-shaped neck sits in a square hole in the fishplate, preventing rotation during installation.
Diamond Neck Track Bolt: This design features a diamond-shaped neck that locks into a matching hole in the rail joint, providing strong resistance to rotation.
Heavy Hex Head Frog Bolt: Used for turnouts (frogs), these bolts have a heavy hexagonal head and are made from a high-strength grade of steel to handle the high stress in these areas.
Hexagon Head Bolt: While less specialized than oval or diamond neck bolts, some fish bolts are manufactured with a standard hexagonal head. However, these are often used in situations where other anti-rotation measures are in place.
Fish bolts vary significantly in size, with typical imperial diameters ranging from 1/2 inch to 1-1/8 inch and metric sizes from M12 to M24, while lengths are selected based on the specific rail profile and fishplate thickness, ranging from around 1-3/4 inches to over 6 inches. Specific sizes are often determined by the rail standard being used (e.g., AREMA, DIN, BS, JIS).
Common Imperial Sizes (approximate)
Diameters:1/2", 5/8", 3/4", 7/8", 1", 1-1/8"
Lengths:1-3/4", 2", 2-1/4", 2-1/2", 3-1/2", 4-1/2", 5-1/2", 6-1/2" and more, depending on the rail section
Common Metric Sizes (approximate)
Diameters:M12, M16, M18, M20, M22, M24
Lengths:45mm - 145mm or upon customer request
Factors Determining Size
Rail Standard:The standard used by a specific railway system, such as AREMA (American), DIN (German), or BS (British), dictates the required fish bolt sizes.
Rail Profile:The height and web thickness of the rail section determine the appropriate length of the fish bolt and the corresponding fish plates.
Fish Plate Thickness:The thickness of the fish plates also dictates the required fish bolt length.
How to Determine the Correct Size？
To find the correct fish bolt size, you must:
1.Identify the rail standard: This is the primary factor in determining the bolt.
2.Measure the rail and fish plates: Determine the thickness of the fish plates and the dimensions of the rail's bolt holes.
3.Consult the relevant standard or manufacturer specifications: Match these measurements to the available standard sizes for that specific rail and standard.
Kunshan Signum Machinery Technology Co.,Ltd is able to supply fish bolts/track bolts according to clients’ requirements or drawing with competitive price.
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Email: admin@rail-fastening.com
Address: 120 Tongjing Road, Lujia Town, Kunshan, Jiangsu 215331, China
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