The material left between perforations is called the bar width. The rule of thumb for perforating carbon steel and aluminum is that the bar width should not be less than the thickness of the material. Keep the bar width greater than the thickness of the material to avoid problems. As the 1-to-1 relationship is approached, the increasing number of punches required sharply escalates the process tonnage needed to perforate the pattern, thus creating potential for problems.

In some cases, variations to these recommendations can be accommodated but with additional production costs.