How Patterns and Hole Shapes Can Influence the Uses of Perforated Metal

In the world of metals and fabrication, appearance can be almost everything. Perforating in some respects, is somewhat of an art form. It has been manufactured using perforating presses for well over a century. As times change, metal perforating evolves as well. Some of the principles behind perforating remain constant, always have and always will, while others have progressed in line with advances in metallurgy and overall technology. Thanks to cnc programming and computer aided design, non-traditional patterns have become available opening the doors for unlimited possibilities including perforated logos and perforated images that resemble just about anything you can imagine. All in all, the perforated patterns have changed, the quality of metals and alloys have improved, and the process of perforating metal has become much more efficient. But lets talk about the perforating patterns specifically.

Every perforated pattern obviously begins with the shape of the hole. Some examples of hole shapes are circular, elliptical, oblong, oval, square, rectangular, hexagonal, octagonal, clover leaf, and triangular. Custom hole shapes are also available by designing a custom perforating tool. Each hole shape brings its own aesthetic characteristics. The layout of the holes can affect the strength of the perforated material. For instance, holes can be perforated in a straight pattern with each hole in perfect line both horizontally and vertically on the metal sheet. Rows of holes can also be staggered which is common practice to maintain strength in the finished product. The straight and staggered patterns create two entirely different appearances. In regards to strength however, a round hole perfed into a staggered pattern produces the best overall strength versus open area. Round holes can be perfed more efficiently and economically than any other hole shape because the dies and punches required to punch a round hole are the easiest and least costly to make. Round hole tooling will also last longer and is easier to maintain. A round hole and staggered pattern is the most commonly commercially perforated pattern for just these reasons.

The hole pattern actually has a direction on a standard mass produced perforated sheet of metal. Take notice of a perforated sheet with a staggered pattern and you'll see that the stagger is typically on the short dimension of the sheet and the straight rows of holes will run parallel to the longer dimension. As for hole size, the one to one rule must be considered. As a rule of thumb, when perforating mild steel and aluminum, the hole diameter needs to be at least the thickness of the raw material for reliable tool performance. In the case of stainless steel in particular, metal thickness should be at least one gauge thinner than the hole width for safer and more reliable production. Regarding the punched patterns in metals another consideration is bar width, or the space between the holes. As with the hole diameter, a one to one ratio of space between holes is the absolute minimum with ease of production increasing width the width of the spacing. Open area is a term used to describe the percentage of metal with holes versus the solid, un-perforated metal. The open area of the sheet will dictate many properties of the finished product including its appearance, of course, as well as its weight, its strength, its ability to absorb heat, its sound absorbing capabilities, and its ability to pass fluids.

Perforated patterns are carefully selected for both their aesthetic appearance as well as their real world performance as a finished product. The combination of hole sizes, hole shapes, and a variety of perforating techniques create an almost endless variety of perforated patterns to choose from.

About the Author: Chet is a 16+ year employee of Hendrick Manufacturing Company, a leader in producing perforated metal plate and metal sheets. Hendrick Mfg. Co. has been in the business of perforated metal continuously in Carbondale, PA since 1876.