Forging

Part of Metalworking

Forging is the art of shaping hot metal with hammer blows. It transforms raw blooms and bar stock into functional tools, hardware, and structural components — the physical backbone of a rebuilding civilization.

Why Forging Matters

A smelted bloom is useless until shaped. Casting can form some objects, but forged iron and steel are stronger, tougher, and more reliable than cast equivalents. Every axe, plow blade, hinge, nail, and chain link your community needs will be forged by hand. Forging also refines metal — each heating and hammering cycle squeezes out slag inclusions and aligns the grain structure, producing progressively better material.

Setting Up the Forge

The Fire

A forge fire is not a campfire. It requires concentrated heat in a small area with controlled air supply.

Component	Purpose	Materials
Fire pot	Contains the fire, concentrates heat	Stone bowl, clay-lined pit, or iron pan
Tuyere	Delivers air to the fire	Clay pipe, iron pipe, or drilled stone
Bellows	Forces air through the tuyere	Leather bag, wooden box bellows
Coal/charcoal bed	Fuel surrounding the workpiece	Hardwood charcoal (preferred) or mineral coal

Building a ground-level forge:

1. Dig a shallow pit 30-40 cm across, 15-20 cm deep
2. Line with clay or flat stones
3. Insert tuyere pipe from one side at the bottom, angled slightly upward
4. Fill with charcoal
5. Connect bellows to the tuyere

Side-Blast vs. Bottom-Blast

A side-blast forge (tuyere enters from the side) is easier to build and maintain. A bottom-blast forge (tuyere enters from below) produces more even heat but clogs with ash more readily. Start with side-blast.

The Anvil

The anvil is the most critical forging tool. Without a proper anvil, precise shaping is impossible.

Improvised anvils (in order of preference):

1. A large flat-topped boulder of hard stone (granite or basalt)
2. A section of railroad rail (if salvageable)
3. A thick steel plate bolted to a stump
4. A large sledgehammer head set in a stump

The anvil must be:

• Heavy (ideally 30 kg or more — heavier absorbs less hammer energy)
• Flat and smooth on the working face
• Mounted at knuckle height when you stand beside it
• Solidly fixed so it does not shift under hammer blows

Essential Tools

Tool	Purpose	How to Make
Cross-peen hammer (1-1.5 kg)	General forging	Forge from a steel block, fit wooden handle
Flat-face hammer (1-2 kg)	Flattening, finishing	Same as above with flat faces
Tongs (flat-jaw)	Holding hot metal	Forge from two bars, rivet at pivot
Tongs (bolt-jaw)	Holding round stock	Same, with curved jaws
Punch	Making holes	Forge from tool steel rod, harden tip
Hardy (hot cut)	Cutting hot metal	Forge a chisel that fits the anvil hardy hole
Wire brush	Removing scale	Twist wire around a handle

Heat Colors and Temperature

Reading heat colors is the smith’s thermometer. Work in dim light when possible — colors are easier to read.

Color	Temperature (C)	Use
Black heat	Below 400	Not forgeable — metal cracks
Dark red	400-500	Tempering only
Cherry red	700-800	Light forging of thin sections
Bright cherry	800-900	General forging range
Orange	900-1,000	Heavy forging, welding prep
Light orange-yellow	1,000-1,100	Forge welding temperature
Yellow-white	1,100-1,200	Maximum forging heat — risk of burning
White/sparking	1,300+	Metal is burning — you have lost it

Burning Metal

If you see sparks flying from the surface of your workpiece in the fire, it is burning — the iron is combining with oxygen and literally disappearing. Remove it immediately. Burned metal cannot be salvaged; it is full of oxide inclusions and will crumble.

Basic Forging Techniques

Drawing Out

Drawing out lengthens and thins a piece of metal. It is the most fundamental forging operation.

1. Heat the section to be drawn to bright cherry or orange
2. Place on the anvil face
3. Strike with overlapping blows, working from the tip back toward the body
4. Rotate 90 degrees and repeat — this prevents the piece from becoming a thin ribbon
5. Reheat as needed — never forge below cherry red

Upsetting

Upsetting thickens and shortens metal — the opposite of drawing out. Used to create bolt heads, nail heads, and thickened sections.

1. Heat only the end to be upset (dip the rest in water to keep it cool)
2. Stand the piece vertically on the anvil, hot end up
3. Strike the top squarely with the hammer
4. The hot section mushrooms and thickens
5. Rotate and true up the shape between strikes

Preventing Buckling

If the heated section is too long relative to its thickness, the piece will buckle sideways instead of upsetting cleanly. Heat no more than 1.5 diameters of length at a time. For longer upsets, work in stages.

Bending

1. Heat the bend location to bright cherry
2. Place the bend point at the anvil edge
3. Strike the overhanging portion downward
4. For sharp bends, use the anvil horn or a bending fork
5. For even curves, bend over a form (a pipe or round bar)

Punching and Drifting

Making holes in hot metal without drilling:

1. Heat the target area to orange
2. Place on the anvil over the pritchel hole (or over empty space)
3. Drive the punch halfway through from one side
4. Flip the piece and drive from the other side until the slug pops out
5. Use a drift (a tapered pin) to enlarge and shape the hole

Cutting

Hot cutting (cutting heated metal):

1. Heat the cut line to cherry red
2. Place on the hardy (a chisel mounted in the anvil)
3. Strike the top of the workpiece to drive it onto the hardy edge
4. Or use a hot-cut chisel held by a handled holder while striking from above
5. Cut most of the way through, then snap the piece over the anvil edge

Forge Welding

Forge welding joins two pieces of iron or steel by heating them until their surfaces become plastic and hammering them together. This is the only welding method available without electricity.

Process

1. Prepare the joint surfaces — scarfed (tapered) ends work best
2. Clean all scale from the surfaces with a wire brush
3. Apply flux — fine silica sand or borax if available
4. Heat both pieces to light orange-yellow (just below sparking)
5. Remove quickly, place one on the other on the anvil
6. Strike firmly and rapidly — the first three blows are critical
7. Continue hammering to consolidate the joint, working outward from the center

Speed is Critical

You have approximately 3-5 seconds between removing the metal from the fire and making your first weld strike. In that time the surface oxidizes and the temperature drops. Have everything positioned and ready before pulling the pieces from the fire. Practice the motion cold before attempting the weld hot.

Flux

Flux dissolves oxide scale on the metal surface, allowing clean metal-to-metal contact:

• Borax — Best flux, if available (found in some mineral deposits)
• Fine silica sand — Adequate for iron-to-iron welds
• Wood ash — Marginal but usable in desperation
• Apply flux to the hot (but not welding-temperature) surfaces, then return to the fire for final heating

Heat Treatment

Hardening

Carbon steel can be hardened by heating to cherry red and quenching (rapid cooling):

1. Heat evenly to bright cherry red
2. Plunge into water (for maximum hardness) or oil (for moderate hardness with less cracking risk)
3. The piece is now very hard but also brittle

Tempering

Hardened steel must be tempered to reduce brittleness:

1. Polish a section of the hardened piece to bright metal
2. Heat gently and watch the color change as a thin oxide film forms
3. The color indicates the temperature and resulting hardness

Temper Color	Temperature (C)	Hardness	Best For
Pale straw	220	Very hard	Razors, engraving tools
Dark straw	240	Hard	Knives, chisels
Brown	260	Medium-hard	Axes, plane irons
Purple	280	Tough	Springs, punches
Blue	300	Flexible	Saws, swords

Quench at the Right Color

When the oxide color reaches your target zone, immediately quench in water to stop the tempering process. If you overshoot, re-harden and try again.

Common Mistakes

1. Forging cold metal — Hammering iron below cherry red causes internal cracks that weaken the piece. Reheat frequently rather than trying to squeeze in extra blows.
2. Uneven heating — Only the heated section is forgeable. Hammering a piece that is hot at the tip but cold in the middle produces uneven thickness and stress concentrations.
3. Striking the anvil — Missing the workpiece and hitting the anvil face directly damages both the hammer and the anvil. Develop accuracy before attempting to work fast.
4. Overheating for forge welds — The difference between welding heat and burning is narrow. Pull the piece the moment the surface looks wet and glistening — do not wait for sparks.
5. Skipping tempering — A hardened but untempered tool will shatter on first use. Always temper after hardening.

Summary

Forging — At a Glance

• A forge requires concentrated fire, forced air (bellows), a heavy anvil, and basic hammer/tongs
• Read heat colors: cherry red for general forging, orange-yellow for welding, never forge below dark red
• Core techniques: drawing out (lengthen), upsetting (thicken), bending, punching, cutting
• Forge welding joins steel without electricity — requires flux, welding heat, and fast hammer work
• Heat treatment (hardening + tempering) converts mild steel into hard tool steel
• Temper colors indicate hardness: straw for cutting tools, blue for springs