How to Forge a Knife From an Old Railroad Spike

Forge something new from something old.

Next Project
Time

A full day

Complexity

Professional

Cost

Varies

Introduction

An art form that spans millennia, bladesmithing recently has seen a surge in popularity. DIYers need to be careful, though — you just might find yourself with a new hobby or profession.

For Jason Kraus, that’s exactly what happened. For more than a decade he’s made swords, daggers and axes. Here, he’ll show us how to make a beautiful knife from an ugly railroad spike.

Tools Required

  • Anvil
  • Belt Sharpener
  • Bench Grinder
  • Forging Hammer
  • Gas forge
  • Safety Gear
  • Tongs

Materials Required

  • Railroad Spike

Meet the Expert

Fh23djf 622 10 091 Bw How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman

A full-time bladesmith for more than 10 years, Jason Kraus has appeared on the hit shows Forged in Fire and Master of Arms. He operates Northstar Forge in Carver, Minnesota.

You’ll Need a Gas Forge

A gas forge is by far the most reliable and controllable type of forge to operate. Coal forges may have old-world charm, but they come with a steep learning curve. To get up to speed quickly, start with gas.

This forge is simple­­ — a propane tank feeds a burner in an insulated chamber. Find one online for as low as $150; search for “gas forge for knife making.”

Project step-by-step (11)

Step 1

Bring Up the Heat

After the forge has come up to temperature, get the steel up to working temperature. Jason secured the railroad spike in a set of tongs and placed it in the forge until it glowed bright orange — about 1,500 degrees.

Fh23djf 622 10 002 How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman

Step 2

Form the Handle

One of Jason’s favorite handle shapes is the simple twist. Once the railroad spike glowed orange, he put it in a vise and twisted it 360 degrees.

Fh23djf 622 10 004 How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman

Step 3

Draw Out the Blade

Once the handle was defined, Jason drew out material on the anvil. He didn’t aimed for a specific shape, just a uniform thickness of 1/4-inches.

Fh23djf 622 10 015 How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman

Step 4

Hammer the Blade Profile

After drawing out the blade material, Jason defined the curved profile of the blade edge by forging the shape with a hammer on the anvil.

Fh23djf 622 10 025 How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman

Step 5

Refine the Blade Shape

Using the grinding wheel, Jason refined the shape by putting a curve in the top of the blade. It’s easier to do this before the heat-treating process.

Fh23djf 622 10 033 How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman

Step 6

Normalize the Steel

Subjecting the steel to multiple heat cycles “normalizes” the particles of the steel, providing a uniform grain structure. Jason heated the blade in the forge and let it air cool five times.

Fh23djf 622 10 052 How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman

  • These two cross-sections of steel show the results of the normalization process. The steel on the left is perfectly normalized; the steel on the right, from a broken knife blade, is poorly normalized.

Fh23djf 622 10 071 072 How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman

Step 7

Quench the Blade

Once the blade was normalized, Jason set the knife back in the forge. He brought the temp up to 1,600 degrees — he could tell by the steel’s bright orange color — and quickly submerged the blade in quenching oil. This thoroughly hardened the steel.

Fh23djf 622 10 061 How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman

Step 8

Temper the Steel

The final step in the heat treatment process, “tempering” softens the steel ever so slightly to produce a blade edge that’s hard but not brittle. For railroad spike knives, Jason used a torch to bring the temperature to 375 degrees and let the blade air cool.

Fh23djf 622 10 070 How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman

Step 9

Grind a Final Time

After the steel was tempered, Jason ground down the blade profile to a fine edge with his belt grinder. To protect his fingers, he held the blade against the platen with a push stick. The blade looked sharp but wasn’t quite there.

Fh23djf 622 10 043 How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman

Step 10

Sharpen the Knife

Jason developed a strong, razor-sharp edge by holding the knife to the belt between the wheels, a process called slack-belt sharpening. With light, even pressure, he drew the blade across a progression of belts. Each was finer than the last, starting at 320 grit and stopping at 3,000 grit.

Fh23djf 622 10 073 How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman

Step 11

Jason’s tools

Bladesmithing calls for safety goggles, a leather apron and these heavy-duty tools.

Tongs

Anvil

  • This 100-year-old anvil came from Sweden.
  • A bladesmith uses an anvil and a hammer to draw out the steel and form the curves of the blade.

Wire brush

  • Jason removes scale with a wire brush while he works the steel.

Rounding hammer

  • Jason forged this 3-lb. hammer himself, and it’s one of his favorites. One side is rounded and the other flat.
    • The rounded head draws out the steel.
    • The flat side removes hammer marks and flattens the steel.

Torch

  • Jason used a MAPP gas torch to temper our railroad spike knife. For everything else, he goes with an industrial oven.

The Twist-o-Matic 3000

  • Jason made this tool himself by welding an adjustable wrench to a monkey wrench.
  • He uses it to twist the railroad spike while it’s held in a vise.

Fh23djf 622 10 078 Tools How To Forge A Unique Knife From An Old Railroad SpikeFamily Handyman