24x230mm Ss36 Sleeper Screw: Specifications and Applications

The 24x230mm Ss36 sleeper screw is a threaded rail fastener used to secure rails (usually through a tie plate) to wooden sleepers in jointed and continuous track. Compared with a plain dog spike, the Ss36 screw engages the sleeper with a full-depth triangular thread, which raises pull-out resistance and holding power and resists the longitudinal and lateral forces generated by braking, acceleration and thermal rail movement.

Design and Function of the Ss36 Sleeper Screw

The Ss36 designation refers to the screw-spike family defined in European and Chinese railway practice for timber-sleeper track. The screw body is hot-rolled from spring or carbon steel, then headed and threaded to the specified profile. When driven into a pre-bored pilot hole, the thread compresses the surrounding timber, producing a firm mechanical lock. This construction keeps the rail foot in position, preserves track gauge accuracy and reduces fastener loosening and wear over long service periods.

Ss36 Series: Length and Rail Height Adjustment

Model	Rail Height Adjustment Range (mm)	Length (mm)	Thread Specification
Ss36 - 260	+29 to +38	260	Common triangular thread
Ss36 - 270	+39 to +48	270	Common triangular thread
Ss36 - 280	+49 to +56	280	Common triangular thread

The 24x230mm Ss36 screw is the base specification in this family; where the rail head height or pad stack changes, the 260-280mm variants provide a controlled vertical adjustment of +29 to +56 mm so that the rail top table can be corrected to the design level.

Ss Series Sleeper Screw Range

The Ss series covers a wide spread of diameters and lengths for light rail, industrial sidings and mainline timber-sleeper sections:

Type	Specification	Weight (kg)	Surface	Standard
Ss 1/130	M22x130	0.451	Zinc, plain, black oil	UIC, AREMA, JIS, GB or per request
Ss 1/150	M22x150	0.478	Zinc, plain, black oil	UIC, AREMA, JIS, GB or per request
Ss 2/180	M22x180	0.595	Zinc, plain, black oil	UIC, AREMA, JIS, GB or per request
Ss 5/150	M24x150	0.545	Zinc, plain, black oil	UIC, AREMA, JIS, GB or per request
Ss 6/130	M26x130	0.658	Zinc, plain, black oil	UIC, AREMA, JIS, GB or per request
Ss 6/150	M26x150	0.702	Zinc, plain, black oil	UIC, AREMA, JIS, GB or per request
Ss 7/180	M24x180	0.636	Zinc, plain, black oil	UIC, AREMA, JIS, GB or per request
Ss 8/140	M24x140	0.528	Zinc, plain, black oil	UIC, AREMA, JIS, GB or per request
Ss 8/150	M24x150	0.548	Zinc, plain, black oil	UIC, AREMA, JIS, GB or per request
Ss 23/160	M23x160	0.645	Zinc, plain, black oil	UIC, AREMA, JIS, GB or per request
Ss 24/165	M24x165	0.590	Zinc, plain, black oil	UIC, AREMA, JIS, GB or per request
Ss 25/165	M25x165	0.625	Zinc, plain, black oil	UIC, AREMA, JIS, GB or per request

Materials, Grades and Surface Finishes

Common raw materials are Q235, 35#, 45# and 55# carbon steels, with strength grades such as 4.6, 4.8, 5.6 and 8.8 depending on service load. Screw spikes are produced by hot forging and the threads are hot-rolled on dedicated thread-forming machines, which preserves the grain flow of the steel and improves fatigue behaviour compared with cut threads.

Standard surface treatments include plain (oiled), zinc plating and black oil. Oiled plain finish protects the screw during transport and initial service; zinc plating adds corrosion resistance for humid and coastal lines; black oil finish is common where the fastener is to be re-coated or kept in dry storage.

Quality Inspection Sequence

Inspection starts at the wire-rod stage, because the quality of the finished screw depends directly on the incoming material. The second step is head-forming inspection, where the tooling (mould) condition is verified; a stable mould is the precondition for a consistent head geometry. The third step checks the formed screw for burrs and confirms the finished dimensions. The fourth step is thread inspection: pitch, flank profile and gauge acceptance must satisfy both the customer drawing and the applicable international standard. The final step is shipment inspection, in which non-conforming pieces are sorted out so that only conforming product is packed for delivery.

Typical Applications

Timber-sleeper mainline and secondary lines where high holding power is required.

Railway turnouts and crossings on wooden bearers.

Mining, industrial and port tracks with heavy axle loads.

Replacement and re-fastening work during sleeper renewal cycles.

Frequently Asked Questions

1. What is the difference between a sleeper screw and a screw spike?

In practice the terms are used interchangeably in railway supply. Both describe a threaded fastener driven into a timber sleeper to hold the rail or tie plate; the Ss designation is one widely used classification of the screw-spike family.

2. Which standards apply to Ss36 sleeper screws?

Ss series screws are commonly supplied to UIC, AREMA, JIS or GB railway standards, or manufactured to a customer drawing or sample. The applicable standard should be confirmed against the project specification because thread profile and gauge differ between systems.

3. Why is a threaded screw better than a dog spike on wooden sleepers?

A threaded screw engages more timber along its length, so pull-out resistance and lateral holding are higher. It also loosens more slowly under vibration and can be re-tightened, which reduces maintenance frequency on busy lines.

4. What surface finish should be chosen for coastal or humid environments?

Zinc plating or hot-dip galvanizing gives the best corrosion resistance for humid or coastal conditions. Plain oiled finish is a low-cost option for dry climates or short storage periods, and black oil suits projects that will re-coat fasteners on site.

5. Can the dimensions or material be customized?

Yes. Non-standard diameters, lengths, thread forms and higher-strength steel grades can be produced on request. Metric, BS, BSW and round thread forms are all available; a pilot-hole diameter matched to the thread is normally specified together with the fastener.

6. How is pull-out performance verified?

Conformance is verified through dimensional inspection, hardness testing and, where required by contract, withdrawal-load testing on a representative timber specimen. The test method and acceptance value should follow the standard cited in the purchase specification.