Forging a knife from a railroad spike is certainly possible, though it requires some metalworking skill and the right equipment. Railroad spikes are made from medium to high carbon steel, so they contain enough carbon to be hardened through heat treating. With the right techniques, you can shape a railroad spike into a functional knife blade.
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What is a Railroad Spike?
A railroad spike, also known as a railway spike or railroad nail, is a large nail with an offset head that is used to secure railroad tracks to railroad ties (the wooden beams that support the tracks). Railroad spikes are roughly 5 to 6 inches long and have a square cross-section of about 3/4 inch.
Railroad spikes are made from medium to high carbon steel for strength and durability. The carbon content ranges from 0.7% to 1.0% carbon. Higher carbon steels are harder and stronger than lower carbon steels, but are also more difficult to machine and forge.
Here are some typical properties of railroad spikes:
| Material | Medium carbon steel |
| Carbon content | 0.7% – 1.0% |
| Length | 5 – 6 inches |
| Cross section | 3/4 inch square |
| Head type | Offset/angular |
The offset head allows the spike to be driven at an angle against the tie for increased holding power. The head is also angled to make it easier to hammer in.
Can You Forge a Knife from a Railroad Spike?
Yes, it is possible to hand forge a railroad spike into a functional knife. Blacksmiths and bladesmiths have forged all kinds of tools and blades from railroad spikes. However, it requires some skill at the forge and knowledge of heat treating.
Here are some key factors to consider:
- Carbon content – Railroad spikes have enough carbon (0.7% to 1.0%) to harden when heat treated. This allows them to hold a sharp edge.
- Forgeability – Railroad spikes can be forged and shaped under a hammer at high heat. The square cross section provides plenty of mass for forming a blade.
- Hardness – A knife blade needs to be hard enough to take a sharp edge, typically Rockwell C 50-55. Railroad spikes can reach this hardness range when quenched after forging.
- Toughness – The medium carbon steel offers a balance of hardness and toughness after tempering, important properties for a durable blade.
- Familiar steel – Many blacksmiths have experience forging medium carbon steels like 1060, which has similarities to railroad spikes.
With the right equipment and knowledge, a railroad spike can be forged into a wide range of knife styles, including bushcraft knives, utility blades, daggers and throwing knives. The relatively simple shape and generous mass of a spike allows plenty of room for creative forging.
The key steps are hot forging to shape the blade, grinding to refine the shape, heat treating to harden the steel, and tempering to improve toughness. Some knife makers may also electrochemically etch or acid wash the blade for extra refinement. With patience and skill, a railroad spike can be transformed into a high quality hand forged knife. The finished knife will have unique character and history from its origin as a rugged railroad spike.
Forging Process
Forging a railroad spike into a knife involves repeatedly heating and hammering the steel while hot to shape it. This is the same basic process blacksmiths have used for centuries to shape iron and steel.
Here is a general overview of the forging process:
- Heat – The spike is placed in the forge fire or other high temperature heat source until it is glowing red/orange. This indicates it has reached a malleable forging temperature, generally around 2000°F for steel.
- Forging – The heated spike is removed from the fire using tongs and placed on the anvil. It is hammered using the cross peen, rounding hammer or other tools to begin spreading the material and shaping the blade.
- Reheating – As the spike cools quickly under hammer blows, it must be frequently reheated to return it to a forging temperature.
- Forming – Over many heating and hammering cycles, the square spike is thinned, tapered, beveled and shaped into the desired blade profile.
- Quenching – Once shaped, the red hot steel is rapidly cooled or “quenched” to harden the steel.
- Tempering – The hardened steel is tempered at lower temperatures reduce brittleness and improve toughness.
Forging thinning and shaping the spike requires planning and skill. The blacksmith must carefully control the heat and hammer blows to move the steel into the desired shape without excessive cracking or folding of the steel. Proper heating temperatures and forging techniques are critical.
The spike can be forged into a wide range of blade styles. Some common profiles made from spikes include drop point hunter knives, tanto style blades, early American/frontier knives, daggers, gurkhas and throwing knives. Spikes have even been forged into ax heads, tomahawks and decorative art pieces.
Forging Tips
Here are some useful tips when forging a knife from a railroad spike:
– Soak the spike in vinegar or another mild acid before forging. This removes surface scale and corrosion to aid forging.
– Always wear safety glasses and other protective gear when blacksmithing.
– Heat the spike slowly and evenly to avoid overheating corners and edges first.
– Use lighter hammer blows while forging the thin cutting edge to avoid unnecessary deformation.
– Normalize the steel by letting it cool slowly after initial forging. This relieves stresses.
– Forge out nicks and cracks as they form to strengthen the steel grain structure.
– Leave enough thickness at the spine and guard to preserve strength in these high stress areas.
– Make sure to align the hammer faces parallel to the blade surfaces during forging. Off-angle blows can cause deformation.
– Constantly check your progress against the planned design and make adjustments as needed.
– Forge the bevels evenly on both sides to avoid twisting problems later.
Following basic blacksmithing principles and best practices will help produce the best possible blade from a railroad spike. Patience and persistence through dozens of heating and forging cycles are essential.
Heat Treating
Once forged into shape, a railroad spike knife must be heat treated to harden and strengthen the steel. Heat treating involves precisely heating and cooling the steel to develop certain microstructures and properties.
Proper heat treatment is crucial for transforming the soft forged steel into a hard, durable knife blade. The main heat treating steps are:
- Hardening/quenching – Heating the steel above a critical temperature before rapidly cooling or “quenching”. This produces a very hard but brittle martensitic structure.
- Tempering – Reheating the quenched steel to a lower temperature for a period. This reduces brittleness by transforming some of the martensite into more ductile structures.
The typical heat treating process for a forged carbon steel knife is:
- Normalize by slowly cooling after forging to relieve internal stresses. This produces a ferritic-pearlitic structure.
- Harden by heating to critical (AC3) temp, around 1500°F for 0.75% carbon. Quench in oil or water.
- Temper between 300-700°F depending on desired hardness. Usually 2-3 tempering cycles.
This results in a complex microstructure of tempered martensite, which provides an ideal balance of hardness (Rockwell C 55-60) and toughness for knife blades.
Proper heat treating requires close control of temperatures and quenching/cooling rates. Too low hardening temperatures or slow quenching can prevent full hardening. Too high tempering temperatures can result in excessive softening.
A variety of methods can be used for heat treating hand forged knives on a small scale:
– Oxy-acetylene or propane forge
– Electric furnace or kiln
– High temperature brine, oil, or air quenching
Testing hardness with a Rockwell tester at various stages can help perfect the heat treating process. For consistent results, the heat treating steps should be performed the same way every time.
Heat Treating Tips
Follow these tips when heat treating railroad spike knives:
– Normalize after forging by slow cooling to relieve stress. Let air cool or bury in ashes/sand.
– Heat slowly and evenly for hardening. Soak at critical temperature for at least 5 minutes.
– Use a quenching medium like fast oil that cools quickly but not too abruptly.
– Temper at or below 400°F for spring steels like 1095. Test different tempering cycles.
– Allow the steel to cool to near room temperature between quenching, tempering, and testing cycles.
– Clean the steel thoroughly after each cycle to observe changes in color and roughness, which indicate tempering.
– Record your entire heat treating schedule including times and temperatures so it can be repeated.
– Only heat treat small batches at a time to ensure consistency.
– Use separate thermometers to constantly monitor temperatures in the forge and quenchant.
Proper heat treating is the culmination of the blade forging process, and essential to creating a functional, durable knife from a railroad spike. It combines skill, precision, and attention to detail.
Grinding and Finishing
Once the railroad spike knife has been heat treated for hardness, the final grinding, polishing and finishing steps can be performed. These final processes refine the shape, create a keen edge, and add aesthetic touches.
Typical grinding/finishing steps include:
- Grinding – Using a bench grinder and files to refine the profile, bevels, plunge lines and other contours.
- Sanding – Progressively higher grit sandpaper or belts to smooth/polish surfaces.
- Buffing – Use buffing wheels charged with compounds to polish steel and create shine.
- Etching – Chemically or electrochemically etch steel to create contrasting finishes.
- Coating – Optionally apply coatings like black oxide, parkerizing or gun bluing.
- Sharpening – Use water stones, ceramic rods, stropping belts, etc. to create a razor sharp edge.
- Handle work – Shape, finish and install handle materials like stabilized wood, micarta, bone, etc.
These finishing steps remove the scale, marks and roughness from forging and heat treating to reveal the form and beauty of the blade. The cutting edge can be honed down to less than .001 inches thick to achieve impressive sharpness. Etching serves both decorative and functional purposes by providing contrast between hardened and unhardened areas.
Sandpapers used range from 80 grit to remove tool marks up to 600-800 grit for final polishing. A high-quality uniform finish is the goal. Multiple stages of buffing with finer compounds can achieve a mirror finish if desired.
It takes skill, patience and attention to detail to fully refine a hand forged knife through grinding and polishing. A full finishing process can take 20 hours or more of meticulous work. The end result is a blade that radiates craftsmanship.
Grinding and Finishing Tips
Here are some useful tips for grinding, polishing and finishing a railroad spike knife:
– Always wear eye protection and a respirator when grinding steel.
– Work through a series of grinding/sanding stages from coarse to fine grit for best results.
– Use a light touch and frequent dipping in water to avoid overheating.
– Blend and feather grinding marks into the overall contours and lines of the blade.
– Follow sanding marks from each previous grit when moving to a finer abrasive.
– Use a file guide or fixed angle system when sharpening to ensure consistency.
– Apply etching solutions evenly over the entire blade unless selectively masking off areas.
– Remove all traces of previous abrasives before moving to finer grits for best results.
– Lubricate buffing wheels and use minimal pressure to avoid wear and burning.
– Clean the blade thoroughly between all finishing steps to observe your progress.
Achieving a fine, consistent finish requires planning the sequence of operations, using the proper abrasives/compounds for each stage, and working with care and patience.
Conclusion
Forged knife making is a unique blend of blacksmithing, metallurgy, craftsmanship and artistry. With proper skills and techniques, railroad spikes can be transformed into highly functional and decorative hand crafted knives. The shaping of the steel under a hammer combined with precise heat treating allows these rugged spikes to be turned into fine cutting tools. Dedication through dozens of heating, forging, grinding and polishing operations can reveal the underlying beauty in common pieces of steel. While it requires substantial effort, the ability to forge history into a handmade knife is extremely rewarding.