# Precision Wire Drawing

> Multi-pass cold drawing through tungsten carbide and single-crystal diamond dies. From φ5.5 mm hot-rolled rod to φ0.025 mm ultra-fine finished wire.


## Drawing Process

### Cold Drawing Sequence

1. **Rod in** — hot-rolled wire rod (φ5.5 mm) enters the multi-pass drawing machine.
2. **Draw** — each pass reduces the cross-section by 15–25% through progressively smaller tungsten carbide dies, with lubricant applied at every die entrance to control friction and temperature.
3. **Anneal** — intermediate H₂/N₂ annealing between passes restores the ductility that cold work removes.
4. **Finish** — after 13 passes the wire reaches φ0.025 mm, thinner than a human hair, held to ±0.005 mm.

### Equipment

- Multi-block continuous drawing line — 13 dies
- Tungsten carbide dies (roughing, φ5.5→0.5 mm)
- Single-crystal diamond dies (finishing, φ0.5→0.025 mm)
- In-line laser micrometer — ±0.001 mm resolution
- Eddy current surface inspection — 100% coverage

## Why diameter tolerance matters

Thermocouple wire diameter directly affects **thermal response time** (halving diameter ≈ 4× faster response), **electrical resistance** (φ0.025 mm **Type K** ≈ 1,900 Ω/m vs φ1.0 mm ≈ 1.2 Ω/m), and **mechanical service life** (doubling diameter ≈ 3× longer fatigue life).

For aerospace engine testing where millisecond response is critical, we supply wire at the fine end of that range. For industrial furnaces with multi-year service intervals, φ1.0–3.0 mm is standard. Our drawing capability spans the full range from one extreme to the other — all from one in-house process with full traceability.