Look closer at your wire drawing dies.
The Hidden Killer: Cobalt Leaching
Polycrystalline diamond (PCD) is made of diamond particles held together by a cobalt binder. During drawing, the extreme heat and pressure can leach cobalt out of the die surface. The diamond grains lose their support, loosen, and create microscopic peaks. Those peaks scratch the soft copper wire. The scratches are tiny — you won’t see them without a microscope — but they act as stress risers. Under tension, the wire breaks exactly at those scratches.
Why Fine Wire Is Worse
Thicker wire (1mm and up) has enough cross‑section to survive micro‑scratches. But fine wire under 0.3mm has almost no margin. A scratch just 5% of the wire depth will cause a break under drawing tension. That’s why your PCD wire drawing dies might run perfectly on 2mm copper but snap on 0.2mm.
The Nano Solution
Nano wire drawing dies use ultra‑fine diamond grains (under 1 micron) and a modified binder system that resists leaching. The smaller grains mean fewer large pull‑outs. Some nano dies also use a nickel binder instead of cobalt, which doesn’t leach under copper drawing conditions.
A Midwest magnet wire plant switched from standard PCD wire drawing dies to nano dies on their fine copper line. Breaks dropped from 12 per shift to 3 per shift. Die life doubled.
What You Can Do
If you can’t upgrade to nano wire drawing dies yet, change your lubricant. A higher viscosity or extreme‑pressure additive can reduce the friction that drives cobalt leaching. Also, reduce die temperature by adding cooling grooves or a mist coolant.
Your PCD wire drawing dies aren’t bad. They’re just leaching. Attack the heat and friction, or switch to nano. Your fine wire will stop snapping, and your scrap bin will stop filling.
