Continuous Wire Drawing from Rod

Commercial wire starts as a coil of hot-rolled rod about 9 mm thick. After the scale is removed, the rod is pulled through a row of ever smaller dies, each wrapped round a driven drum, or block, that pulls it on to the next; one machine may hold 3 to 12 dies. Each die takes away 15–25 % of the area on fine wire and 20–45 % on heavier wire, and the wire gets longer as it gets thinner. Cold drawing makes it stronger; if the total reduction passes about 50 % it is annealed before drawing on. High-carbon steel rod gives music wire, stainless rod stainless wire, and copper rod copper wire, which may get a final anneal for ductility and conductivity.