What a Fish Plate Is and What It Must Fit
A fish plate, also called a joint bar or splice bar, is a steel plate bolted to the web of two adjacent rail ends to keep them aligned and to carry the bending moment across the joint. Its size is not a free choice: the plate profile must match the rail web contour, the bolt holes must match the rail's drilling pattern, and the length must give enough bolts and bearing surface to keep the joint rigid under traffic. A plate that is too short or too thin lets the joint dip; one with the wrong hole pattern cannot be bolted at all. The starting point for any fish plate order is therefore the rail section - its standard, its mass per metre, and its hole drilling.
Key Dimensions of Fish Plates
Length: standard bars range from about 200-600 mm; heavy-duty bars for 50-60 kg rails run from 600-800 mm, and special joints can reach about 1100 mm.
Thickness: standard bars are about 20-30 mm; heavy-duty bars for high-tonnage joints are thicker, up to about 38 mm.
Hole pattern: normally 4 or 6 bolt holes per bar, spaced and sized to the rail's drilling; hole diameter is matched to the bolt, commonly 25-28 mm for heavy rails,.
Weight: light-rail bars weigh about 5.5 kg, mainline 4-hole bars about 14-18 kg, and heavy 6-hole bars over 26 kg.
Size Tables by Standard
| Standard | Rail Type | Configuration | Weight |
|---|---|---|---|
| AREMA | 115RE | 4-hole, 24 in or 610 mm, | 17.04 kg |
| AREMA | 115RE | 6-hole, 36 in or 915 mm, | 25.56 kg |
| AREMA | 132-136RE | 4-hole, 24 in or 610 mm, | 17.75 kg |
| AREMA | 132-136RE | 6-hole, 36 in or 915 mm, | 26.63 kg |
| UIC 864 | UIC60 | 4-hole, 630 mm, hole 26 mm | 18.07 kg |
| UIC 864 | UIC60 | 4-hole, 600 mm, hole 28 mm | 17.47 kg |
| UIC 864 | UIC60 | 4-hole, 630 mm, hole 25 mm | 18.10 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 | BS60A | 4-hole | 5.61 kg |
| BS 47-1 | BS80A | 4-hole | 6.50 kg |
| BS 47-1 | BS90A | 685.8 mm, hole 26 mm | 13.23 kg |
| BS 47-1 | BS90A | 792.9 mm, hole 26.2 mm | 15.34 kg |
| BS 47-1 | BS100A | 4-hole | - |
| AS 1085 | AS 50 kg | 4-hole | 14.30 kg |
| AS 1085 | AS 50 kg | 6-hole | 19.50 kg |
| DIN / EN | S49 | 4-hole | 9.71 kg |
| AREA/ASCE | 90/91 lb | 4-hole | 18.08 kg |
| AREA/ASCE | 90/91 lb | 6-hole | 19.90 kg |
Fish plates for these sections are normally machined from medium-carbon steel with about C 0.42-0.50, Mn 0.50-0.80, Si 0.17-0.37, Cr ≤ 0.25, P ≤ 0.035 and S ≤ 0.035 percent by mass, normalized or quenched and tempered to the specified hardness, then drilled to the hole pattern.
Special Joint Bars and When They Are Used
| Joint Bar Type | Construction | Typical Use |
|---|---|---|
| Insulated rail joint bar | Steel bars with composite insulating end posts and bushings; electrical resistance above 10^8 Ω | Track circuit boundaries and signal sections |
| Compromise joint bar | Each end machined to a different rail profile | Joining different sections, e.g. UIC54 to UIC60 |
| Joggled joint bar | Depressed centre section keeps the rail head surface continuous | High-speed jointed sections where wheel impact must be minimised |
| Bridge joint bar | Longer and thicker, reinforced web | Bridge approaches and high-stress locations |
| Glued insulated joint | Bars bonded to the insulation with high-strength adhesive | Long-life insulated joints on main lines |
How to Specify a Fish Plate
State the rail standard and section such as UIC60 to UIC 864 and 115RE to AREMA - this fixes the web profile.
State the hole configuration: 4-hole or 6-hole, hole diameter, spacing and end distance; supply the drilling drawing if it differs from the standard.
State the material and hardness requirement, plus the coating if the joint is in a corrosive environment.
State the bolt specification - fish plate bolts are supplied with matching nuts and washers, and bolt grade must suit the clamping load.
For insulated joints, add the electrical resistance requirement and the insulation material.
Common Misconceptions
"One fish plate fits many rail sizes." The plate profile mirrors the rail web; a UIC60 plate does not seat on a UIC54 rail, and vice versa.
"Longer plates are always stronger." Length must match the drilling and the joint design; an over-long plate with holes outside the rail's bolt range cannot be fastened at all.
"Fish plates and rail are made of the same steel." Plates are machined from plate steel and heat treated to match the rail's strength and toughness - the composition above is typical of the plate grade, not the rail grade.
"Insulated joints are a special order for metro systems only." Every track-circuited line uses them; they are standard products with a defined electrical specification.
FAQ
What is the standard length of a fish plate for 60 kg rail?
UIC60 bars are typically 600-630 mm with 4 holes; heavier and longer 6-hole versions are used where the joint carries more bending, and some national designs run to 800 mm.
How many bolt holes does a joint bar have?
Normally 4 or 6 per bar; the hole diameter , commonly 25-28 mm on heavy rails, and spacing must match the rail drilling and the bolt size.
How much does a fish plate weigh?
From about 5.5 kg for light-rail bars such as BS60A to 26 kg and more for heavy 6-hole bars such as AREMA 136RE 36-inch versions.
What is a compromise fish plate?
A joint bar whose two ends are machined to two different rail profiles, allowing two different rail sections to be bolted together in one joint, for example when changing from UIC54 to UIC60.
Can a fish plate be reused after removal?
Not recommended. Plates develop bolt-hole wear and fatigue from service; reusing a plate transfers hidden damage to the rebuilt joint, so plates are normally renewed together with the bolts when a joint is reconditioned.