Dog Spike Sizes: Standard Dimensions for Timber Sleepers
Sep 30, 2025
What Is a Dog Spike?
A dog spike, also called a cut spike or cut track spike, is a large nail with a square shank and a wedge-shaped tip, used to fasten T-rail and tie plates to timber sleepers. The head is offset to one side, and the underside of the head is sloped so that it sits on the sloping flange of the rail base or on the shoulder of the tie plate. The spike is driven across the grain of the sleeper with the wedge parallel to the track, which gives a strong mechanical grip without splitting the timber. Its main job is to keep the rail in gauge and to hold the plate firmly against the sleeper.
Standard Dog Spike Sizes
The size designation gives the shank diameter and the length in inches. The following sizes are the most frequently specified for timber-sleeper track:
| Size | Shank (in) | Length (in) | Typical use |
|---|---|---|---|
| 5/8 x 6 | 5/8 | 6 | Standard main line timber track, standard tie plates |
| 9/16 x 5-1/2 | 9/16 | 5-1/2 | Smaller rail sections, light branch track |
| 1/2 x 3-1/2 | 1/2 | 3-1/2 | Light industrial and yard track |
| 3/8 x 3-1/2 | 3/8 | 3-1/2 | Very light track, temporary lines |
The 5/8 x 6 and 9/16 x 5-1/2 are the two most popular sizes in the North American market, especially in the United States. Other lengths and shank diameters are available to order; for non-standard sections it is normal to manufacture from the customer's drawing or sample.
How the Spike Geometry Works
Three features decide how well a dog spike holds: the head, the shank, and the tip. The offset head presses down on the rail flange or plate shoulder, converting the clamping force into vertical restraint on the rail. The square shank fills the hole left by the wedge tip and resists rotation, so the spike cannot work loose under vibration. The wedge-shaped tip is driven across the grain, which compresses the wood fibres and locks the spike in place. The slope under the head must match the rail base slope, typically 1:4 or 1:2.75 depending on the rail section, which is why the spike and the rail section should be specified together.
Materials and Mechanical Properties
Dog spikes are made from carbon steel, commonly A3 or Q235, with 45# or 55# steel used for higher hardness on demand. For heavy-duty service, spikes are specified to a minimum tensile strength and hardness range, and batch tested before shipment. The steel must be tough enough to be driven without the head breaking off, yet hard enough to resist wear at the rail seat. Phosphorus and sulfur are kept low to avoid brittleness in the driven spike.
Finishes and Corrosion Protection
Standard supply is plain with an oil film for rust protection. Where the track is exposed to rain, salt, or humidity, hot-dip galvanized or zinc plated spikes are available; the coating must be applied after heat treatment so that the mechanical properties are not affected. For yard and workshop track, plain oiled spikes are usually sufficient and are the most economical choice.
Packing and Handling
Dog spikes are heavy, loose items and are normally packed in kegs. The common pack weights are 200 lb, 100 lb, and 50 lb kegs, which match the quantities used by track gangs and keep the spikes easy to handle on site. When ordering, confirm the pack weight, the coating, and whether head and tip dimensions must match a specific rail base slope.
Frequently Asked Questions
1. What is the difference between a dog spike and a screw spike?
A dog spike is hammered in and holds by compression of the wood around the wedge tip; a screw spike is rotated into a pre-drilled hole and holds by thread engagement, giving higher pull-out resistance. Dog spikes are faster to install, screw spikes are easier to remove and re-use.
2. What size dog spike is most common?
The 5/8 x 6 in spike is the most common size for main line timber track in North America, with the 9/16 x 5-1/2 in used for lighter rail sections. The right size depends on the rail section and the tie plate.
3. How deep should a dog spike be driven?
The spike should be driven until the underside of the head presses firmly on the rail flange or plate shoulder without cutting into it. Over-driving bends the head and damages the rail seat; under-driving leaves the fastening loose.
4. Can dog spikes be driven into concrete sleepers?
No. Dog spikes rely on the elastic grip of timber. For concrete sleepers, screw spikes with plastic dowels or elastic fastening systems are used instead.
5. Which standard applies to dog spikes?
In North America, AREMA track material specifications cover cut spikes; in other regions, spikes are supplied to national railway standards or to customer drawings. Confirming the head slope and shank dimensions against the drawing is the safest way to specify.
6. Do spikes need to be pre-drilled for?
No. Dog spikes are driven directly into the sleeper; the wedge tip compresses the wood rather than cutting a hole. Pre-drilling is used for screw spikes, not for cut spikes.
