Choosing the Right Hole Shape & Pattern for Your Perforated Product

Perforated tubes and other perforated products are widely used in a myriad of filtration, dampening, exhaust, drainage, and other industrial applications. Holes contained within perforated products are created using a combination of standard and/or custom punches, CNC punching pattern software, and special fabrication techniques. The size of the holes in the perforated tube or other product is typically determined by the application—for example, by the size of contaminants the tube must filter out.

Architectural Applications for Perforated Products

Due to their wide range of practical and aesthetic features, perforated metal is popular among architects and designers. You’ll find them being used in an array of applications, including:

• Lighting fixtures
• Conduit ducts
• Safety guards

Perforated metal is common as interior design elements, in which they allow light or air to be exchanged. They may also be used to dampen unwanted noise.

Choosing Perforated Metal Tubes for Your Application

Perforated tubes come in many different patterns. Ultimately, the design and application requirements will determine the perforation styles, or if the seams of the tubing contain perforations.

Metalex offers two primary seam designs for perforated spiral tubes: the flush (outside) and inside lock seam, which are popular for use in fluid filtration. We also offer a unique spiral louvered design with a flushed lock seam, used as an alternative to the straight seam tube when a weld is not required. Other seam designs include various welded and abutted options.

Perforated tubes come in an assortment of materials to meet the requirements of the specific application. Materials used in the manufacture of perforated tubing include:

• Tin plated
• Galvanized metal
• Stainless steel
• Brass
• Aluminum

The material will be application-specific based on the demands of the environment or the aesthetics required. For example, perforated tin plated metal tubes are common in filtration type applications, while perforated stainless steel, brass, and aluminum tubes are used as architectural elements.

Shapes

The types of hole shapes available in perforated products are limited only by the ability to machine cutting dies into a specific configuration that can create the shape and withstand the stresses of the punching process. Below are the most commonly used and most cost effective hole shapes:

• Round Holes. A round hole is the easiest and most economical shape to incorporate into perforated sheet metal, as the relative simplicity of machining a round piece results in low manufacturing costs. Round hole patterns are used in a variety of applications, including air-conditioning and heating systems and decorative finishes for architectural installations.

• Square Holes. Square holes provide a significant amount of open area and a clear view through finished sheets, while also offering a strong barrier that can be used to resist impact loads, prevent contact with equipment, or prevent entry of trespassers into protected areas. Increased wear on equipment occurs during the square hole perforation process due to the tendency of the punches to experience increased stresses near the corners of each square shape. For this reason, the creation of square hole patterns has increased costs over the production of round holes.

• Slot Holes. Slot holes consist of long rectangles with half-circle or square ends. These are versatile shapes in the manufacturing industry, as they are applicable to screening and sorting of materials—particularly long thin items such as seeds and grains. Slots can be installed parallel to either the width or the length of the sheet, depending on user preference and needs of the

Patterns

Straight line and staggered patterns represent the most common designs used for perforating metal. These fit the majority of perforated metal uses. Non-standard patterns are also available for custom applications.

• Straight Line. Straight-line perforated metal layouts consist of repeating rows that contain an identical number of holes in each row and follow the same alignment down the sheet as it is pulled through the punch. Straight patterns are designed by specifying both the distance between holes and the distance between successive rows of holes.

• Staggered Layouts. Staggered layouts consist of repeated patterns that offset alignments of adjacent rows as the sheets are pulled through the punch. Staggered layouts are specified based on the angle between centers of successive lines of holes. For instance, one of the most common patterns is a 60° staggered pattern. This means that after one row of holes is punched, the die moves over and punches the next row, so the line drawn from the center of a shape on the previous line to the center of an adjacent shape on the new line forms a 60° angle.

• Non-Standard. Non-standard patterns—such as circle, spiral, and star patterns—increase the cost of the perforation process, primarily as a result of the increased production time required to create these layouts. As with the hole shapes, utilization of patterns that are relatively symmetrical can reduce the overall cost of the perforated sheets.

Hole shapes and patterns have a sizeable impact on the cost and performance of your perforated product. Knowing these specifications helps eliminate roadblocks when you bring a project to a manufacturer. To learn more about the qualities of perforated products, download our free eBook, Proper Selection for Perforated Products.

Perforated Products from Metalex

Metalex was founded in 1962 and has grown from a small one-machine operation to a prominent member of a global group of manufacturers. We are dedicated to providing our customers with the highest quality products at the lowest possible cost. When you’re selecting perforated tubing for a particular application, our customer service representatives are available to offer advice on appropriate choices for any industry or application.

To learn more about our perforated products and how Metalex can help you achieve significant efficiencies and cost reductions in your operation, contact us or request a quote.

3 Traits of Perforated Sheets to Identify before Ordering from Your Manufacturer

Perforation of material is accomplished by using mechanical means to penetrate, or “punch”, through material surface, leaving behind a hole of particular size and shape. In practice, perforated material typically consists of flat sheets that are modified by creating recurring patterns of punched shapes.

Implementation of perforated products into any project requires knowledge of the cost implications associated with specific metal configurations. It is important to understand the various characteristics of a sheet and the options available when specifying the product to be produced.

Before ordering custom perforated sheets, the buyer must typically specify these three traits:

1. Material Type and Thickness

There are many types of materials suitable for perforating, with what is most applicable for the specific projects dependent upon the material cost and properties. Commonly used materials for perforated metal are:

• Hot-rolled and cold-rolled carbon steel
• Galvanized Steel, typically pre-galvanized (galvanized prior to punching)
• Stainless steel (Type 304 and 316, both standard and low carbon varieties)
• Aluminum
• Brass
• Copper

Material thickness is also important to consider, especially since the cost of fabricated pieces is typically derived from the “per pound” price of the material, and perforated pieces are no exception. The thinner the perforated sheets, the less material used to create the finished piece, and therefore the lower the price per piece.

In addition to simply saving on material cost, it is easier for shops to punch and work thin(ner) sheets than it is to machine thicker pieces, which creates an associated savings in production costs as well. It is important to remember, however, that decreasing the cross-section of the sheets by choosing a lesser thickness will create a decrease in the structural capacity of the sheet.

Utilization of higher-strength pieces can, in some cases, result in an overall reduction in the number of pieces that are required. The designer must balance material thickness versus structural requirements to ultimately decide on the best way to achieve a cost-efficient project.

2. Hole Shape and Size

Perforated product producers are able to create a wide array of hole shapes and patterns in material sheets through the use of standard and custom punches, computerized punching pattern programs and special fabrication techniques.

• The types of hole shapes available in perforated products is limited only by the technological ability to machine the cutting dies into a specific configuration that can not only create the shape, but withstand the stresses of the punching process. A round hole is the easiest and most economical shape to incorporate into a perforated sheet, as the relative simplicity of machining a round piece results in low manufacturing costs.
• Hole size is determined by drawing a circle around the hole shape with a radius that extends from the center of the shape to its extreme outside edge. Typically the hole size is greater than or equal to the thickness of the material being punched, in most cases much greater. For high-strength material such as stainless steel, the hole size must generally be at least 2 to 3 times the thickness of the metal sheet in order to provide a clean cut, easier manufacturing and reasonable cost.

3. Margins

The end margin width on perforated sheets is normally zero, which means that there is no distance between the perforated patterns and the end of the sheet. This is known as an “unfinished pattern” and occurs when the punching continues to the ends of the sheet and the holes do not complete their last cut cleanly inside the sheet borders.

Stock sheets are most commonly available in an unfinished pattern configuration. It is also the least expensive way to fabricate a piece from scratch. If desired, a minimum margin width can be created on the ends, but require adjustments to the perforation process, resulting in more expensive sheets.

Learn More about Criteria Involved in Manufacturing Perforated Sheets

Knowing the exact specifications of your perforated product can help accelerate the project’s completion — and lets you know what to expect in terms of cost and timeline. To learn more about the factors that go into selecting your product, download our new eBook, Proper Selection for Perforated Products.