Application Matching

Part of Wire Drawing

Choosing the right wire type and gauge for each use in a rebuilding civilization.

Why This Matters

Wire is one of the most versatile materials in a rebuilding civilization, but using the wrong wire for a given task wastes precious resources and creates dangerous failures. A copper wire sized for jewelry will melt if used to carry generator current. An iron wire meant for fencing will snap if used as a musical string. Every meter of wire costs hours of labor at the draw bench, so matching wire to application before you begin drawing saves enormous effort.

In an industrial society, engineers consult standardized tables and order from catalogs. In a post-collapse setting, you must understand the underlying principles yourself. You need to know which metal suits which purpose, what diameter handles which load or current, and how surface finish and temper affect performance. Getting this wrong does not just waste material — it can start fires, collapse structures, or destroy irreplaceable equipment.

This article provides the decision framework for matching wire to task. Once you internalize these principles, you can make confident choices even with unfamiliar metals or novel applications, adapting your limited wire stock to the widest possible range of needs.

Metal Selection by Application

The first decision is always which metal to use. Each has distinct properties that make it suited to specific roles.

Copper

Best for any electrical application. Copper has the second-highest electrical conductivity of any metal (after silver) and excellent corrosion resistance. Use copper wire for:

• Power transmission from generators to loads
• Motor and transformer windings
• Telegraph and communication lines
• Lightning conductors
• Electrical connections and jumpers

Copper is also highly ductile, meaning it draws easily through dies without frequent annealing. Its main drawback is relatively low tensile strength — it stretches under heavy mechanical loads.

Iron and Mild Steel

Best for structural and mechanical applications where strength matters more than conductivity. Use iron wire for:

• Fencing and animal enclosures
• Binding and lashing in construction
• Nails and fasteners (cut from wire)
• Springs (with proper carbon content)
• Snares and traps
• Guy wires and cable reinforcement

Iron wire is cheap to produce from bloomery iron but rusts readily. Coat with grease, tar, or — if available — zinc (galvanizing) for outdoor use.

Brass and Bronze

Good compromise between workability and corrosion resistance. Use for:

• Marine and wet-environment fasteners
• Decorative work
• Musical instrument strings (bronze)
• Electrical contacts where spring tension is needed (brass)

Precious Metals (Silver, Gold)

Reserve for specialized applications:

• Silver: best possible electrical contacts, medical sutures
• Gold: corrosion-proof contacts for critical switching equipment

Gauge Selection

Wire diameter determines both the load a wire can carry (mechanical or electrical) and how much material you consume. The goal is always to use the thinnest wire that safely handles the job.

Electrical Gauge Selection

For electrical wire, the critical factor is current capacity (ampacity). Wire that is too thin for its current load overheats, destroying insulation and starting fires.

Current (Amps)	Minimum Copper Diameter	Typical Use
0.5-1	0.5 mm	Signal lines, telegraph
1-3	0.8 mm	Low-power lighting (single lamp)
3-7	1.2 mm	Multiple lamps, small motors
7-15	1.8 mm	Workshop tools, larger motors
15-30	2.5 mm	Heavy equipment, main feeds
30-50	3.5 mm	Generator output leads

Distance Matters

These figures assume short runs under 15 meters. For every additional 15 meters, go up one size to compensate for voltage drop. A 50-meter run to a distant building needs wire roughly twice the diameter of a 5-meter indoor run at the same current.

Mechanical Gauge Selection

For structural wire, tensile strength is what matters. Iron wire can support roughly 400 MPa before breaking; copper only about 200 MPa.

Wire Diameter (mm)	Iron Breaking Load (kg)	Copper Breaking Load (kg)
1.0	32	16
1.5	72	36
2.0	128	64
3.0	288	144
4.0	512	256
5.0	800	400

Safety Factor

Always apply a safety factor of at least 4:1 for permanent structural applications. If your load is 50 kg, use wire rated for at least 200 kg breaking strength. For life-safety applications (bridge cables, elevator mechanisms), use 8:1 or higher.

Temper and Hardness Matching

Wire fresh from the draw bench is “hard-drawn” — stiff, springy, and strong but brittle. Annealed wire is soft, flexible, and easy to bend but weaker. Matching temper to application is critical.

Use Hard-Drawn Wire For:

• Springs
• Musical strings
• Fencing (maintains tension)
• Guy wires and stays
• Structural reinforcement

Use Annealed (Soft) Wire For:

• Electrical windings (must bend tightly around cores)
• Binding and tying
• Jewelry and decorative work
• Forming complex shapes
• Knitting into mesh or chainmail

Use Half-Hard Wire For:

• Electrical transmission lines (needs some stiffness to span poles)
• Hooks and formed hardware
• Staples and clips

To anneal wire, heat it to a dull red glow (about 600-700 C for copper, 750-800 C for iron) and let it cool slowly. To achieve half-hard temper, draw soft wire through one additional die reduction after annealing.

Surface Finish Requirements

Surface condition affects both performance and longevity.

Bright finish (clean, polished): Required for electrical connections. Oxide layers increase resistance dramatically. Achieve by drawing through well-lubricated dies and storing in dry conditions.

Tinned (coated with tin): Ideal for electrical wire that will be soldered. Dip clean copper wire in molten tin. Also provides moderate corrosion protection.

Tarred or greased: Appropriate for outdoor iron wire. Dip in hot pine tar or coat with rendered fat after drawing. Reapply annually for long-term installations.

Galvanized (zinc-coated): The gold standard for outdoor iron wire. Requires a zinc supply and careful temperature control (zinc melts at 420 C, burns above 500 C). Dip clean iron wire in molten zinc for 30-60 seconds.

Common Application Reference Table

This table summarizes the recommended wire specification for the most common rebuilding-era applications.

Application	Metal	Diameter (mm)	Temper	Surface
Generator winding	Copper	1.2-2.0	Soft	Bright, insulated
House wiring	Copper	1.5-2.5	Soft	Insulated
Telegraph line	Copper or Iron	2.0-3.0	Half-hard	Bright or tarred
Fence wire	Iron	2.5-4.0	Hard	Galvanized or tarred
Binding wire	Iron	1.0-1.5	Soft	Any
Nails (cut from wire)	Iron	2.0-4.0	Hard	None
Springs	Steel (high-C)	0.8-2.0	Hard	Oiled
Snare wire	Brass or Steel	0.5-1.0	Half-hard	Bright
Musical strings	Bronze or Steel	0.3-1.2	Hard	Bright
Chainmail rings	Iron	1.2-1.8	Half-hard	Oiled
Sutures	Silver or Iron	0.2-0.4	Soft	Boiled (sterile)
Lightning rod conductor	Copper	4.0-6.0	Any	Bright

Decision Process

When you need wire for a new application, work through these questions in order:

1. What is the primary function? Electrical conduction, mechanical strength, or forming/shaping?
2. What environment will it operate in? Indoor/dry, outdoor/wet, underground, submerged?
3. What loads must it handle? Amps for electrical; kilograms for mechanical.
4. What flexibility is needed? Must it bend repeatedly, hold a shape, or remain rigid?
5. How long must it last? Temporary (weeks), semi-permanent (years), or permanent (decades)?

The answers to these five questions will narrow your choice to one metal, one diameter range, one temper, and one surface treatment. When in doubt, err toward thicker wire and more corrosion protection — the labor cost of replacing failed wire in an installed system far exceeds the material cost of using slightly more wire initially.

Inventory Strategy

Maintain stock in three standard diameters of each metal you produce: a fine gauge (0.5-1.0 mm), a medium gauge (1.5-2.5 mm), and a heavy gauge (3.0-5.0 mm). This covers the vast majority of applications without requiring custom drawing for every new project.