railroad spike

A railroad spike is a large, heavy nail, typically 5.5 to 6 inches long, driven through the base of a rail and into a wooden sleeper (or tie) to fix the rail in place. The spike has a relatively small head, a thick square or slightly tapered shaft, and a blunt point; this geometry allows it to pierce wood without splitting it lengthwise. The weight and mass of a railroad spike, usually between 1 and 1.5 pounds, give it the momentum needed to drive deep into hardwood sleepers under a single or double hammer blow.

Railroad spikes are made from mild steel and are available in several standard sizes. The most common in North America are the 6-inch and 6.5-inch lengths, with shaft diameters around 0.5 inches. Spikes are typically driven at an angle of 20 to 45 degrees from vertical, leaning slightly toward the center of the sleeper, which increases holding power and helps distribute load. A single rail section may be secured with 4 to 8 spikes per sleeper, depending on line speed, axle load, and track geometry.

Why they work and where they fail

The spike's holding power comes from friction and the deformation of wood fibers around the shaft. However, this grip weakens over time due to wood shrinkage, vibration from train traffic, and the chemical weathering of the spike itself. Spikes can loosen, slip, or pull entirely from the sleeper, causing gauge widening (the distance between rails increases) and dangerous track misalignment. Rust, which reduces the spike's diameter, accelerates this failure. In high-speed or heavy-haul service, elastic fastening systems (spring clips or other devices) have replaced or supplemented spikes to maintain tighter gauge control.

The term "railroad spike" is distinctly American; in Britain and many Commonwealth nations, the equivalent fastener is called a "rail spike" or simply a "spike", and earlier designs included shouldered spikes with a flat shoulder below the head to resist sideways pull. The spike name itself reflects its kinship to the common nail, though a railroad spike is far heavier and harder to drive by hand. Early American railroad construction in the 1830s and 1840s adapted blacksmith-forged spikes from general carpentry, and machine-driven spike manufacture became standard by the 1870s.

Modern railroad maintenance still involves spike inspection, removal, and replacement, though hydraulic spike pullers and pneumatic drivers have replaced manual methods on most main lines. Spike wear is a predictable maintenance cost and an important indicator of track condition. Loose spikes are dangerous and must be driven back or replaced immediately; a well-maintained spike can remain in service for decades, but high-speed or freight-intensive routes may require full spike replacement every 20 to 30 years depending on load and climate.