What Is an Ideal Rail Joint? Strength, Continuity and Fishplate Data
Dec 31, 2025
What an Ideal Rail Joint Looks Like
An ideal rail joint behaves as if it were not there. It gives the track the same strength and stiffness as the rail itself, keeps both rail ends perfectly in line, allows the rail to move with temperature, and can still be removed and replaced when maintenance requires it.
In practice this is approached in two ways: by welding rails into continuous welded rail, or by using a well designed bolted or insulated joint whose stiffness is as close as possible to that of the parent rail.
Key Characteristics of an Ideal Joint
Strength and stiffness - able to carry the same loads and impacts as the parent rail without breaking or deflecting under traffic.
Continuity and alignment - rail ends stay in line both horizontally and vertically, so wheels do not hop or deviate at the joint.
Elasticity - flexible enough to absorb vibration and dynamic forces in the same way as the rest of the track.
Thermal movement - provides the freedom the rail needs to expand and contract as temperature changes.
No rail end batter - protects the rail ends from the flattening that shortens the life of ordinary joints.
Easy maintenance - one rail can be removed, replaced or adjusted without disturbing the whole line.
Economy - low first cost together with minimal and cost effective maintenance.
Fishplate Types That Meet Different Needs
Standard fishplates - the general purpose joint bar pair for joining two rails of the same section on plain line.
Compromise fishplates - designed to join rails of different sizes or profiles, and essential at transition sections where the rail section changes.
Insulated fishplates - stop electrical current passing between joined rail ends, and play a central role in track signalling and control systems.
Heavy duty fishplates - used on heavy haul and crane rail installations to withstand high loads and severe conditions.
All of these joints are made to international standard requirements, including BS, UIC, GB, AREMA and DIN profiles, and non standard joints can be produced to a customer drawing when a track uses a special section.
Standard and Crane Rail Fishplate Data
The table gives the main dimensions of common fishplates for 43 kg, 50 kg and 60 kg rails and for QU series crane rails.
| Rail type | Length (mm) | Width (mm) | Thickness (mm) | Hole dia. (mm) | Hole spacing (mm) | Bolt size |
|---|---|---|---|---|---|---|
| 43 kg rail fishplate | 800 | 65 | 16 | 22 | 90 / 105 | M22 |
| 50 kg rail fishplate | 800 | 65 | 20 | 24 | 100 / 120 | M24 |
| 60 kg rail fishplate | 860 | 70 | 20 | 24 | 100 / 120 | M24 |
| QU70 crane rail fishplate | 760 | 70 | 20 | 24 | 90 / 105 | M24 |
| QU80 crane rail fishplate | 820 | 75 | 20 | 24 | 100 / 120 | M24 |
| QU100 crane rail fishplate | 950 | 80 | 22 | 26 | 105 / 125 | M27 |
| QU120 crane rail fishplate | 1050 | 85 | 26 | 26 | 110 / 130 | M27 |
Fishplates are produced in carbon steel or alloy steel and are supplied oiled, galvanized or painted, depending on the environment and the maintenance policy of the operator.
Rolled and Forged Joint Bars
Workshop fabricated joint bars are available in both rolled and forged versions. Forged bars are chosen where a tighter fit and higher fatigue performance are needed, and both types can be sandblasted, oiled or hot dip galvanized.
| Model | Material | Unit weight | Surface treatment |
|---|---|---|---|
| SJ50 rail joint | 50# | 11.59 kg/pc | Plain |
| SJ43 rail joint | 50# | 10.16 kg/pc | Plain |
| TJ57 rail joint | 45# | 17.36 kg/pc | Plain |
| S30 rail joint | 50# | 5.8 kg/pc | Plain or as required |
| CR135 rail joint for CR135 crane rail | 50# | per drawing | Plain or hot dip galvanized |
| CR171 rail joint for CR171 crane rail | 50# | 16.0 kg/pc | Plain or hot dip galvanized |
| S49 forged rail joint | Q345 | 8.60 kg/pc | Sandblasted and oiled |
| S60 forged rail joint | Q345 | 14.50 kg/pc | Sandblasted and oiled |
More than fifty sets of rolling and forging dies are available, so both standard and non standard joints can be produced, and design adjustments can be made for a specific track or crane rail section.
Frequently Asked Questions
Q: Can any bolted joint be as good as continuous welded rail?
A welded joint removes the gap completely and therefore gives the best ride and the longest rail end life. A well designed bolted joint can approach that performance, but it always introduces some discontinuity in stiffness and geometry.
Q: When are compromise fishplates needed?
At any location where two rails of different section or weight meet, such as the transition between heavy haul track and a lighter yard or siding.
Q: Why do insulated joints need special attention?
They carry both structural and electrical duty, so the end post, bushes and washer plates must be correctly fitted and the joint must stay tight. A loose insulated joint fails quickly and causes signalling faults.
Q: What causes rail end batter?
Batter comes from repeated impact at a joint that is not perfectly aligned or not fully tight. The wheel strikes the rail end, the metal deforms, and the defect grows until the rail end has to be cut and re drilled.
Q: How are fishplate dimensions specified?
Length, width, thickness, hole diameter, hole spacing and bolt size are all matched to the rail section and to the drilling pattern of the standard being used.
Q: Which standards can fishplates be supplied to?
Fishplates are produced to BS, UIC, GB, AREMA and DIN profiles, and special joints for crane rails and non standard sections are made to drawing.
