Spike Hardness Range
The hardness of a carbon steel rail spike is carefully controlled to provide durability without brittleness. A typical range for a medium-carbon steel spike is 200 to 300 HB, or about 15 to 32 HRC. This balance ensures the spike can withstand driving impacts without shattering, while also resisting wear and deformation under load. A spike that is too hard breaks under the hammer; one that is too soft bends and loses holding power, so the hardness specification is a key quality check.
Chisel Point Design
The chisel point on a cut spike serves two functions. First, it helps the spike penetrate the wood fibers of the sleeper by cutting through them rather than tearing, which reduces the driving force. Second, it orients the spike correctly during installation: the chisel is set perpendicular to the wood grain, which helps prevent the spike from splitting the sleeper. Correct orientation matters as much as correct driving, because a spike driven with the chisel parallel to the grain acts like a wedge and splits the sleeper.
Moisture Content of Sleepers
Moisture content is critical to spike performance. If a sleeper is too dry, it becomes brittle and prone to splitting when the spike is driven. If it is too wet, the wood compresses too easily and does not provide sufficient grip. Spikes are designed to be installed in sleepers with an optimal moisture content, typically around 20 to 30 percent for treated wood, to ensure maximum holding power. Maintenance crews should check sleeper condition before driving new spikes.
Spikes vs Screw Spikes
A cut spike and a screw spike are different fasteners with different jobs. A lag screw or screw spike is typically larger in diameter with a coarser thread, designed to be turned into a pre-drilled pilot hole and to pull itself down tightly to clamp a baseplate. A screw spike often has machine-style threads and may be used with an insert in concrete, focusing more on vertical restraint. The cut spike is driven, not turned, and works by friction and compression in the wood. The correct fastener must be matched to the sleeper type and the baseplate design.
Safety Protocols for Manual Driving
Key protocols include wearing safety glasses with side shields to protect from flying metal chips or scale, and heavy-duty non-slip gloves to protect the hands. The worker must ensure a clear swing zone to avoid striking others, use a properly sized sledgehammer with a secure head, and inspect the hammer and spike puller for damage before use. The spike should be held with a proper holder or tongs, never by hand, and the work area kept clear of loose tools. When pulling old spikes, the same eye and hand protection applies, and the puller must be positioned so that a slip does not cause injury.
Frequently Asked Questions
What hardness should a rail spike have? Typically 200 to 300 HB, balancing durability against brittleness for driving impact and service load.
Why does the chisel point matter? It cuts wood fibers for easier penetration and, set perpendicular to the grain, prevents the spike from splitting the sleeper.
What sleeper moisture is optimal for spikes? around 20 to 30 percent for treated wood, providing grip without brittleness or excessive compression.
What is the difference between a cut spike and a screw spike? screw spike is turned into a pilot hole to clamp a baseplate, while a cut spike is driven and works by friction and compression.
What are the key safety rules for manual spike driving? Eye and hand protection, a clear swing zone, a secure hammer head and inspection of tools before use.