When it comes to buying expanded metal products, how do you know you are getting what you pay for?
If you bought a bag of sugar and got home to discover it was half filled with sawdust, you’d demand your money back and probably report the store to the authorities. If you ordered ¾ #9 standard expanded metal and it arrived in a different size or gauge, would you realize you had been cheated? Could you measure it to see if it conforms to the specification? Do you even know there is a specification?
Many service centers purchase and stock expanded metal sheet. The Expanded Metal Manufacturers Association has spent the last three years updating EMMA 557-15, the Standard for Expanded Metals. EMMA is working with the American Society of Testing Materials to assure that its specification, ASTM F-1267-15, is also mathematically and physically accurate. Below is an introduction to both specs.
To identify the product, it helps to be familiar with some basic nomenclature. First, the “pattern” is determined by the user’s needs and is designated by the diamond size and the material thickness. Over time, industry practice has made some of these designations less accurate. For instance, ½ #13 (stated as “half thirteen”) has a half-inch opening and is made from 13-gauge steel. Conversely, ¾ #9 has an opening of 0.923 inch and is made from 10-gauge material.
Besides the pattern, users must consider whether they need “standard” (also called raised or regular) or “flattened” expanded metal. Raised material, with its multiple facets, is what comes out of the expanding press. Flattened material has been run through a cold mill. Standard material is often used for its traction, in a ladder or catwalk for example, while flattened material might be used for a grilling surface.
Finally, the sheet size must also be specified. Expanded products typically are produced in 4-by-8 sheets, but many sizes are available. Sheets also can be sheared to produce custom sizes.
To confirm that the product delivered is what was ordered, four dimensions can be measured (see graphic):
- Long Way of Diamond (LWD)—the nominal dimension measured from one point on a bond to that same point on the next bond.
- Short Way of Diamond (SWD)—the nominal measurement going the other direction.
- The Strand Width—the amount of metal fed under the dies to produce one strand.
- Strand Thickness—the thickness of the base metal.
Here’s the rub—the thickness of the material and the width of the strand can be varied to create slightly different openings. This is perfectly allowable since there is variation within gauges of base metals. As thicker material is used to produce a given product, the strand width can be reduced to compensate, thereby keeping the weight per square foot the same. The issue is that some producers may utilize thinner materials and still narrow the strand width, delivering an inferior product.
To protect themselves, buyers should take the following steps. First, order the material produced to EMMA 557-15 or ASTM F-1267-15 standards. Next, weigh the sheet. Standard weights are published per 100 square feet. On a buy of ½ #13 flat carbon steel, a 4-by-8 sheet should weigh 40.32 pounds, plus or minus 10 percent. If the sheet delivered weighs less than 36.29 pounds, the product is substandard. On grating products, which are typically load bearing, the allowed variation is limited to plus or minus 5 percent.
Specialty or made-to-order products are often produced to an engineering drawing rather than any specification. These are generally designed for a specific purpose and might be produced to meet some other, more important criteria, such as fitting into a jig. Manufacturers of shopping carts, lockers or furniture often have their own internal requirements for expanded metal. They may legitimately differ from the normal, pattern-sized sheets generally stocked and sold by metal service centers.
Measuring standard expanded metal can be tricky even for the most experienced warehouse person armed with good calipers. It’s critical to ensure that the measuring surfaces are flat with the plane being measured. Because of all the angles in expanded metal, getting into the diamond becomes an exercise in patience. To measure the strand thickness, the calipers must be flat against the thickness of the bond. Standard or raised expanded metal should not be reduced in thickness from the base metal from which it was made.
There are very few differences between the two expanded metal specifications. EMMA 557-15 does not require the accompaniment of a producing mill test report, whereas ASTM-F-1267 does. Dimensionally, both specs are identical. Any producer can manufacture product that meets either of these specifications without being a member of the Expanded Metal Manufacturers Association or the American Society of Testing Materials. Nor does a company have to be a North American producer to meet these specifications. To protect themselves from receiving inferior products, service centers would be well advised to source expanded metal from suppliers, both domestic and foreign, that adhere to these standards.
The Expanded Metal Manufacturers Association (EMMA) is a division of the National Association of Architectural Metal Manufacturers (NAAMM), headquartered in Glen Ellyn, Ill. The group’s mission is to promote the use of various architectural metal products through the development and distribution of technical standards. EMMA 557-15 is available on-line and can be downloaded at www.naamm.org/division/publications/4
Exmet Industries, Inc., Vancouver, B.C.
Phone: 604-988-5265 Web: www.exmet.com Expanded Solutions
, Oklahoma City, Okla.
Phone: 405-946-6791 Web: www.expandedsolutions.com New Metals, Inc.
, San Antonio, Texas
Phone: 888-639-6382 Web: www.newmetals.com Spantek Expanded Metal
Phone: 952-935-8431 Web: www.spantek.com