24x161mm Plain Oiled Ss25 Sleeper Screw: Specs and Applications

The Ss25 sleeper screw is a key threaded fastener of the railway track system. It fixes the rail, usually through a tie plate, to the timber sleeper and holds the track gauge stable under the longitudinal and lateral forces generated by train operation. Its full-length thread distributes the holding load through the timber, giving higher clamping force and pull-out resistance than a plain dog spike and slowing the loosening process caused by vibration.

The 24x161mm Plain Oiled Variant

The 24x161mm Ss25 screw is a plain-oiled version of the Ss25 family: nominal thread diameter 24mm and overall length 161mm. It is manufactured from high-strength carbon or alloy steel by hot forging, with the thread hot-rolled on dedicated thread-forming machines so that the steel grain follows the thread contour and fatigue resistance is preserved.

What Plain Oiled Finish Means

Plain oiled means the screw is protected by a thin film of anti-rust oil instead of a paint or plating layer. The oil film prevents corrosion and wear during storage and transport, reduces friction during driving, and improves installation efficiency. In humid or coastal environments the oil film extends service life, although zinc or hot-dip galvanized finishes give longer corrosion protection where the climate demands it. Because the oil film is thin, the screw thread profile and gauge remain accurate to drawing.

Ss Series Sleeper Screw Range

Type	Dimension (mm)	Weight (kg)
Ss5-150	M24x150	0.545
Ss8-140	M24x140	0.528
Ss8-150	M24x150	0.548
Ss8-160	M24x160	0.568
Ss23-160	M24x160	0.645
Ss25-165	M24x165	0.625
Ss35-161	M24x160	0.657

The 24x161mm Ss25 screw sits within this family; the table shows the standard Ss range used as reference for tendering and replacement orders. Weights are per piece before packaging. Non-standard diameters, lengths and higher strength grades can be produced to customer drawings or samples.

Manufacturing and Materials

Rail screw spikes are produced mainly by hot forging. The threads are hot-rolled, which gives a denser surface and better fatigue life than machined threads. Metric, BS, BSW, TR (trapezoidal) and round thread forms are available. Typical raw materials are Q235, 35#, 45#, 40Mn2 and 20MnSi carbon and low-alloy steels; for screw spikes the strength grade is commonly specified in the 4.6-8.8 range depending on sleeper type and axle load.

Typical Applications

High-speed railway lines where gauge stability and low maintenance are critical.

Heavy-haul freight lines with high axle loads and strong traction forces.

Urban transit and metro depot tracks on timber sleepers.

Turnouts, crossings and bridge approaches on wooden bearers.

Industrial sidings, mining railways and temporary works.

Installation Notes

For maximum holding power, drill a pilot hole of the recommended diameter and depth, keep the screw axis vertical, and drive with a machine that allows torque control so that the timber is not over-compressed. Where the tie plate is used, seat the screw head fully in the plate slot before final torqueing. On re-fixing work, clean the old hole or move the spike position slightly so that the thread bites fresh timber.

Frequently Asked Questions

1. What does Ss25 mean in railway fastening?

Ss25 is one of the screw-spike designations used in timber-sleeper fastening practice, identified by its thread diameter and length, here M24 x 165mm (with the 24x161mm variant supplied on request). It is part of a family that includes Ss5, Ss8, Ss23, Ss35 and Ss36.

2. How is the plain oiled surface different from zinc plating?

Plain oiled screws carry only a thin oil film, which is inexpensive and adequate for dry climates and short storage. Zinc plating or hot-dip galvanizing adds a metallic barrier and is preferred for humid, coastal or chemically aggressive environments.

3. Why use a screw spike instead of a dog spike?

The threaded engagement of a screw spike distributes the holding load along the full length of the shank, increasing pull-out resistance and reducing loosening under vibration. This makes screw spikes the standard choice for higher-speed and heavier-axle-load timber-sleeper track.

4. Which standards apply to Ss series sleeper screws?

Ss series screws are supplied to UIC, AREMA, JIS and GB railway standards or to customer drawings and samples. Thread form, gauge and mechanical property requirements differ between systems, so the applicable standard should be fixed at enquiry stage.

5. Can the 24x161mm screw be supplied with another finish?

Yes. The same Ss25 geometry can be produced with zinc plating, black paint, color paint, hot-dip galvanizing or plain finish, and the length and thread can be adapted to the sleeper section and rail height.

6. How is quality controlled before shipment?

Control covers incoming wire rod, head-forming tooling, burr and dimensional checks, thread pitch and gauge verification, and final shipment sorting so that only conforming screws are packed, matching the inspection sequence described in the general screw-spike quality procedure.