24x230mm Hot Dip Galvanized Ss36 Sleeper Screw

What the 24x230mm Ss36 Is For

The 24x230mm Ss36 is an extra-long member of the sleeper screw family: 24 mm nominal shank diameter and 230 mm overall length. Sleeper screws fix the sole plate or ribbed baseplate to the sleeper, holding the whole fastening assembly down so that the rail, pad, and plate stay in position. Most sleeper screws are 130-180 mm long; the 230 mm length is specified where the fastening must engage deeper - for example, with thick timber sleepers, heavy baseplates, or where the track design calls for a longer embedment to develop higher pull-out resistance.

Where Extra Length Matters

Longer sleeper screws are used in several situations:

Thick timber sleepers - the screw must pass through the plate and engage a sufficient depth of timber to develop full holding power.

Ribbed and sole plates - plates with a raised profile take up part of the screw length above the sleeper surface, so a longer screw is needed to keep the embedment depth.

High pull-out demand - turnouts, bridge approaches, and heavy-haul sections subject fastenings to higher forces, and deeper engagement increases the resistance to withdrawal.

Re-drilled sleepers - in maintenance, a longer screw can restore holding power in a sleeper whose original hole has been enlarged or damaged.

The Hot Dip Galvanized Finish

Hot dip galvanizing applies a thick zinc coating by immersion in molten zinc, giving the screw a corrosion protection that plain oiled screws do not have. The coating protects the thread, the collar, and the head, which are exactly the areas exposed to moisture and salt on outdoor track. For coastal lines, tunnels, and industrial sidings, the galvanized finish extends the interval between renewals and keeps the fastening tight for longer. Galvanizing is carried out after heat treatment, so the strength of the screw is unaffected.

Use with Timber and Concrete Sleepers

On timber sleepers, the Ss36 screw is driven with a power wrench into a pre-drilled pilot hole; the hole diameter is matched to the timber so the long thread cuts cleanly without splitting. On concrete sleepers, the screw is threaded into a plastic dowel that is cast into the sleeper during manufacture. The dowel protects the concrete from local crushing and makes the fastening demountable, so a worn screw can be replaced without damaging the sleeper. In both cases, the screw works with the baseplate, rail pad, and rail to complete the fastening system.

The Sleeper Screw Family

The Ss36 belongs to a wider family of sleeper screws that share the same principle but differ in geometry:

Ss series sleeper screws - the metric family with the highest volume in service, in a range of diameters and lengths.

Square head screw spikes - the classic style for timber fastening, tightened with a socket.

Hexagon head screw spikes - for higher tightening torque and defined preload.

Double head screw spikes - where the head must sit flush or countersunk.

Dog screws and timber screws - related threaded fasteners for specific sleeper and plate arrangements.

All of these can be supplied with the same hot dip galvanized finish, so a complete project can use one corrosion protection standard.

Specification Points

When ordering 24x230mm Ss36 screws, confirm the shank diameter, overall length, threaded length, head style, material grade, and finish. Because the collar and head geometry differ between national standards, a drawing or sample is the fastest way to fix the profile. Batch inspection before packing should cover dimensions, thread fit, and mechanical properties, and the coating thickness should meet the galvanizing standard applied to the order.

Frequently Asked Questions

1. Why is a 230mm sleeper screw needed when most are 130-180mm?

The 230 mm length is used where the fastening must engage deeper into the sleeper - thick timber sleepers, high-profile baseplates, or positions with high pull-out demand such as turnouts and bridge approaches.

2. Can the 24x230mm screw be used in concrete sleepers?

Yes, with a plastic dowel cast into the concrete sleeper. The screw threads into the dowel, which gives a strong, demountable fastening.

3. What does hot dip galvanizing add to the screw?

A thick zinc coating that resists corrosion at the thread, collar, and head. It is the recommended finish for coastal, high-humidity, and industrial environments.

4. What steel is used for Ss36 sleeper screws?

Q235 carbon steel is the common standard, with 35# or 45# medium carbon steel for higher strength. Where defined, mechanical property classes follow ISO 898-1.

5. Does galvanizing affect the strength of the screw?

No. Galvanizing is applied after heat treatment, so the mechanical properties are unchanged. The zinc coating adds corrosion protection only.

6. How is the long screw installed without splitting the sleeper?

The sleeper is pre-drilled with a pilot hole sized for the timber species. The screw is then driven with a power wrench at controlled speed and torque, so the thread cuts cleanly without splitting the wood.