<— click here to return to main perforated metal page
Glossary / Tolerances Perforated Metal
Round Perforations – Staggered (60 degree pattern) is standard. Variations include 45 Degree Staggered, and Straight Line Pattern
Square Perforations – Staggered Pattern or Straight Line Pattern
Slotted Perforations – Side Staggered, End Staggered, or Straight Lines. Slotted Perforations will be round end slots; specify if square end slots are required.
Pattern of Perforations
Unfinished End Pattern – The condition which occurs with some specifications of staggered pattern perforations as a result of tool design. On one end of the plate, the pattern will appear to be incomplete due to unperforated holes in the even numbered rows while on the other end of the same plate, the pattern will appear to be incomplete die to unperforated holes in the odd-numbered rows.
Finished End Pattern – The condition which occurs with some specifications of staggered pattern perforations as a result of tool design, where the pattern is completed on both ends of the plate.
Staggered Perforations, both round and square – Direction of the stagger will normally be the short dimension of the sheet, as illustrated in Fig. No.3 Straight row of holes is normally parallel to long dimension of sheet.
Slotted Perforations – The long dimension of the slots can be furnished parallel with either the width or length of the sheet in most cases.
Formulas for Determining Percentage of Open Area
Staggered Round Holes
Square Holes (Straight or Staggered)
45 Degree Staggered Centers Pattern (Special)
Square End Slot
Perforated Stock Size Sheets and Plates – The long sides of the sheet will be supplied with minimum margins. The short sides of the sheet will have either minimum margins or no margins
Sheets and Plates Resheared after Perforating – Special margins are available to specifications but they must carry a tolerance within the limits of the perforating tool. Unfinished end pattern is standard in the industry.