The recommended contact point on the reduction zone of a die should be 75% to 100% of the wire diameter. The bearing (or land) of a die is downstream of the drawing cone, and although it plays no part in the prior reduction in area of the wire, it does help to preserve the wire size. A bearing surface that is too large will increase the drawing stress because of friction.
This course presents a classification of wire breaks from a perspective that compares material defects to process-related problems. Rod defects will include both casting and rolling issues such as internal voids, foreign contaminants, rolled-in scale, hot cracks, and surface porosity. The effects of wiredrawing speed and lubrication will be discussed with respect to generation of fines, shaving, galling, and other surface defects.
Misalignment is one of the biggest problems that exists in drawing of copper wire and other metals and alloys, and one of the worst places is the rod breakdown machines.