The Three Dimensions That Decide Fit
An e-clip does not fit because it looks similar to the old one; it fits because three dimensions match. The first is the groove, meaning the diameter, width and depth of the seat in the base plate or shoulder into which the clip is driven and in which it bears. The second is the clip's own free diameter, measured across the coil before installation; this dimension sets how much the clip has to be deflected to reach its working position and therefore how much toe load it will generate. The third is the bar diameter of the spring steel, which controls stiffness and the load the clip can carry without taking a permanent set. A clip with the correct free diameter but a heavier bar will be too stiff for the seat and will either not drive home or will overstress the shoulder.
Reading a Clip Drawing Before Ordering
A usable clip drawing shows the free diameter, the installed height, the leg form, the bar diameter, the material grade and the required hardness. From these values the toe load at the working deflection can be verified against the fastening design. Where a clip is supplied against a sample or a drawing only, ask for the toe load figure at the installed position, because two clips of the same outline and different bar diameter can differ by a large margin in the load they apply to the rail foot. Measuring a used clip is not a reliable way to size a replacement, since a clip that has been in track may have relaxed or taken a set.
Matching the Clip to the Rail Section and Sleeper
The clip works with the rest of the fastening: rail pad, base plate or tie plate, shoulder or insert, and the sleeper material. Rail geometry is fixed by the section standard, for example the profiles in GB/T 2585-2007, and the clip seat is machined or cast to suit that profile. On timber sleepers the assembly usually includes a tie plate and a drive-in spike or a screw spike, on concrete sleepers a cast-in shoulder or a plastic dowel, and the clip form differs between the two. When changing from one sleeper type to another, the clip, the seat and the pad must be reviewed together rather than clip alone.
Reference Dimensions for Common E-Clips
| Clip type | Free diameter | Unit mass | Material grade |
|---|---|---|---|
| E1609 | 16 mm | 0.43 kg | 60Si2MnA |
| E1809 | 20 mm | 0.61 kg | 60Si2MnA |
| E1813 | 18 mm | 0.62 kg | 60Si2MnA |
| E2007 | 20 mm | 0.80 kg | 60Si2MnA |
| E2009 | 20 mm | 0.80 kg | 60Si2MnA |
| E2055 | 20 mm | 0.80 kg | 60Si2MnA |
| Type III | 18 mm | 0.80 kg | 60Si2MnA |
| Tension clip, 13 mm bar | 13 mm | 0.48 kg | 60Si2CrA |
| Tension clip, 13 mm bar | 13 mm | 0.53 kg | 38Si7 |
| Heavy duty clip | 20 mm | 0.97 kg | 60Si2MnA |
| Light clip | 13 mm | 0.25 kg | 60Si2MnA |
Material Grades and Their Composition
Rail clips are forged from spring steel and then quenched and tempered. The grades in common use and their chemical composition requirements to GB/T 1222-2016 are shown below; equivalent supply specifications include DIN 17221 and BS 970. The grade decides how much deflection the clip tolerates without taking a permanent set, so a change of grade is a change of product and requires re-qualification of the toe load.
| Grade | C | Si | Mn | Cr | P max | S max |
|---|---|---|---|---|---|---|
| 60Si2MnA | 0.56-0.64 | 1.60-2.00 | 0.60-0.90 | 0.35 max | 0.030 | 0.030 |
| 60Si2CrA | 0.56-0.64 | 1.40-1.80 | 0.40-0.70 | 0.70-1.00 | 0.030 | 0.030 |
| 55Si2Mn | 0.52-0.60 | 1.50-2.00 | 0.60-0.90 | 0.35 max | 0.030 | 0.030 |
| 38Si7 | 0.35-0.42 | 1.50-1.80 | 0.50-0.80 | - | 0.030 | 0.030 |
Hardness, Fatigue Life and Surface Finish
Hardness after quenching and tempering is normally specified in the range of 44 to 48 HRC for e-type clips and 42 to 47 HRC for tension clamps. The fatigue requirement is expressed as cycles without fracture at the working deflection: a common reference is 3 million cycles for clips formed from 18 mm bar and 5 million cycles for clips formed from 20 mm bar. Surface condition matters as much as the material, because a forging lap or a deep scratch becomes a fatigue initiation point. Standard finishes are plain and oiled, oxide black or colour painted, and where corrosion protection is required a zinc-based coating is used, with cut or damaged areas repaired after installation.
Frequently Asked Questions
Q: How do I measure an e-clip to find its size?
A: Measure the free diameter across the coil with the clip unloaded and measure the bar diameter at a straight section away from the bend. Then compare both with the seat dimensions in the base plate or shoulder, since a matching diameter with the wrong bar diameter will not give the designed toe load.
Q: Can I replace a 20 mm clip with an 18 mm clip of the same shape?
A: Not without checking the design. Bar diameter sets stiffness and toe load, so a lighter bar reduces the clamping force on the rail foot. The substitution should be confirmed against the fastening design data.
Q: What grades are used for rail clips?
A: Common grades are 60Si2MnA, 60Si2CrA, 55Si2Mn and 38Si7, with chemical composition to GB/T 1222-2016. The grade determines the deflection the clip can accept without permanent set.
Q: What hardness should a rail clip have?
A: Typically 44 to 48 HRC for e-type clips and 42 to 47 HRC for tension clamps after quenching and tempering. Hardness outside the range usually means a problem with the heat treatment cycle.
Q: How is fatigue life of a clip specified?
A: As a number of load cycles at the working deflection without fracture. A common reference is 3 million cycles for 18 mm bar clips and 5 million cycles for 20 mm bar clips, tested on a sample from each production batch.
Q: Why does my clip come out bent after installation?
A: The clip has been over-deflected, usually because it was driven into a seat of the wrong depth or the shoulder was not fully formed. Check that the free diameter and the seat groove match the drawing, and drive the clip with the correct tool.