What Are Rail Screw Spikes?
Railroad spikes are a common type of rail fastener used to connect the steel rail and the railway sleeper. There are many types of spikes, including screw spikes and dog spikes. From the appearance point of view, the most prominent difference between the screw spike and the ordinary spike is that the surface of the spike has an obvious thread. A thread is a shape having a uniform spiral protrusion on a section of the outer or inner surface of the solid. According to its structural characteristics and uses, screw spikes can be divided into several categories.
Main Types of Screw Spikes
Screw spikes are produced in several head and shank configurations to suit different fastening systems and driving methods.
SS Series Sleeper Screws
The SS series includes models such as SS1/130, SS1/150, SS2/180, SS5/150, SS6/150, SS7/180, SS8/140 and SS8/150, covering thread diameters from M22 to M26 and lengths from 130 to 180 mm.
Square Head Screw Spike
The square head screw spike is the classic form for timber sleepers and is produced to UIC, AREMA, DIN or GB standards, or according to customer drawings or samples.
Hexagon Head Screw Spike
The hexagon head form suits mechanical driving and repair work. Several sizes are available, such as M22 by 145 mm, M22 by 155 mm, M22 by 165 mm, M22 by 185 mm and M22 by 195 mm.
Double-Head Screw Spike
The double-head screw spike has threads at both ends and is always used together with a spring clip fastening system. It is especially popular in African markets for concrete sleeper track.
Manufacturing Process
The screw spike is produced through a controlled process chain: raw material inspection, wiredrawing, rod cutting, head forming, edge cutting, thread rolling, heat treatment, surface treatment, final inspection, packing and shipment. Thread rolling is preferred over cutting because it improves the fibre structure of the thread flanks and increases fatigue strength. Heat treatment sets the final mechanical properties, and surface treatment such as zinc plating or oiling protects the spike during storage and service.
Technical Requirements for Screw Spikes
Screw spikes can be applied to fasten railway ties, sleepers or railway turnouts, and they can also be used in conjunction with plastic ferrules cast into concrete ties or sleepers. Railroad turnouts are made up of many railway accessories, and in order to ensure safe driving, the quality of each railway accessory must be guaranteed. Only qualified spikes can guarantee the safety of driving. The technical requirements cover the material grade, the mechanical properties, the thread accuracy, the head geometry and the surface finish, and each batch should be verified by inspection before delivery.
Screw Spikes versus Dog Spikes: Selection Points
There are two common types of railroad spikes: the dog spike and the screw spike. The dog spike is a plain steel spike driven into a timber sleeper, and it holds the rail mainly by friction and the compression of the timber. The screw spike has a thread that is screwed into the sleeper, which gives a much stronger grip and a higher resistance to pull-out under train loads. The screw spike can also be removed and re-installed during maintenance, while a dog spike damages the timber when it is pulled out. Because of these advantages, screw spikes have become the standard for mainline track, especially with concrete sleepers and plastic ferrules.
Choose the spike type according to the sleeper material and the fastening system. For concrete sleepers, use screw spikes with plastic ferrules so that the spike can be removed for maintenance. For timber sleepers, both square and hexagon head screw spikes can be used, or dog spikes for lighter track. Match the thread diameter and length to the base plate hole and the sleeper thickness, and specify the surface treatment according to the climate. During maintenance, retighten loose spikes and replace any spike with damaged threads.
A common misconception is that all railroad spikes are the same. Screw spikes and dog spikes have completely different holding mechanisms and applications. Another misconception is that a longer spike is always better; the length must match the sleeper thickness and the embedment depth so that the point does not split the sleeper. It is also often assumed that screw spikes can only be used in timber; in fact they are widely used in concrete sleepers together with plastic ferrules.
Frequently Asked Questions
What is a rail screw spike? It is a threaded fastener used to connect the steel rail and the railway sleeper, giving a strong grip and high pull-out resistance.
What is the difference between a screw spike and a dog spike? screw spike is threaded and screwed into the sleeper, while a dog spike is driven in and relies on friction.
What sizes are available in the SS series? Models range from SS1/130 at M22 by 130 mm to SS8/160 at M24 by 160 mm, with more models on request.
Which head types are available for screw spikes? Square head, hexagon head and double-head forms are available.
Can screw spikes be used with concrete sleepers? Yes, they are used together with plastic ferrules cast into the concrete sleeper.
Why is thread rolling used in manufacturing? Thread rolling improves the fibre structure of the thread and increases the fatigue strength of the spike.
