Sheet metal, to state the obvious, is metal that has been transformed into sheet form, like a sheet of plywood or a sheet of drywall. Many people equate the term “sheet metal” with the silvery or spangly-looking metal one might see as part of their household duct work. Similarly, sheet metal workers are often equated to HVAC or duct workers, fabricating thin, galvanized metal into rectangular-shaped duct.
Sheet metal, however, has an enormously larger market than traditional duct work. Sheet metal, in fact, is one of the most fundamental forms of metal used in manufacturing today.
Believe it or not, sheet metal originates from coils. This is hard to explain, but sheet metal is originally manufactured using a process that rolls the sheet into a tight coil. These coils are generally transported in the United States, by trains and railcars.
Most large sheet metal processing plants have rail spurs and unload these coils to process them into flat sheets, or sheet metal shapes.
These processers have special machines called levelers. Leveling machines can be massive and are very impressive machines that take large metal coils and roll them out to make flat sheets. The metal, in many cases, is actually flattened, stretched and cut to length.
Coils come in various widths. Common sizes are four-feet wide and five-feet wide. Once these coils are leveled the same machine will cut the now flat sheets into stackable sizes. A very common sheet size is ten-feet long or twelve-feet long. Most processing plants will inventory hundreds and hundreds of sheets in various metal gauges and sheet sizes.
The most common sheet metal size is likely four-foot wide by ten-foot long.
Another common size is five-foot wide by ten-foot long.
Processing plants will also customize sheet cut lengths if their customers order enough material to justify running a specific size. This can be very helpful, for example, to avoid wasting material with awkward cut sizes. For example, cutting a six-foot blank out of a ten-foot sheet is quite wasteful, leaving a four-foot remnant.
Downstream from coil processing plants are the traditional sheet metal fabrication plants like All Metals Fabrication (AMF). These types of manufacturing facilities utilize the raw sheets to manufacture end user goods. Sheet metal can be ordered in multiple thicknesses (or gauges) and multiple material types. We will explain this in more detail below.
Understanding that sheet metal is the start of things like automobile bodies, plane fuselages, major appliances, roofing and architectural panels, light-rail train skins and so much more, and one might begin to perceive how prevalent this type of metal is in the manufacturing industry.
Many different types of metal can be processed into sheet form, including aluminum, brass, copper, steel, titanium, tin and stainless steel, to name some common ones.
Sheet sizes also come in multiple thicknesses. Sheet metal thickness is measured in gauges; the higher the number, the thinner the sheet metal. The most commonly-used sheet metal sizes range from 26 gauge (thinner) to 7 gauge (thicker).
A sheet metal gauge tool is used to measure metal thickness and shows both the gauge number as well as the thickness of the metal in thousandths of an inch. Gauge thickness applies differently depending on the metal type, which is confusing but just how it is. Ferrous and non-ferrous metals, for example, classified by the same gauge, actually have different thicknesses. In order to avoid confusion, most shops measure steel and stainless steel products by gauge and non-ferrous metal, like aluminum, copper, brass, by decimal thickness.
It should be noted that aluminum is usually classified by inches rather than by gauge, as there is no official gauge standard for aluminum. The difference in thickness for each gauge size is based on the weight of the sheet for each different type of metal. This handy sheet metal thickness chart shows gauge size by inches and metal type.
All of this can be a bit confusing but like most things it becomes easier to understand with experience in the industry. Most skilled sheet metal workers can spit out decimals in place of fractions, including gauge sizes, just like grade school A,B,C’s.
This kind of experience and knowledge is critical for success in the industry because so much depends on it. Gauge size determines so many things—nozzle sizes for laser cutting, calculating bend deductions for metal stretch during forming, welding processes, etc.—are all dialed in based on the thickness of the metal.
Sheet metal also has thickness tolerance, meaning not every sheet called out as a certain gauge is precisely the same. Sheet gauge tolerance absolutely plays a role in manufacturing sheet metal. Ryerson, for example, provides their tolerance range, in this example, for stainless steel. If one looks at the right column, he/she can see very small decimal variations that may apply; these tolerances are very small. For example .0030″ is approximately the thickness of a human hair. However, even variations as tiny as these can impact fabrication processes like forming. Small variations in batches of metal can cause inconsistencies in very precise fabrication processes.
Sheet metal and gauge size, changes to what the industry calls plate metal after crossing over 7GA (.188). After that, metal is measured and called out by decimal equivalents. A ¼”-thick metal is called out, you guessed it, by .250.
Sheet metal fabrication and plate metal fabrication are very often different niches. It is hard, for example, for a company that excels at sheet metal to also excel at plate metal. It simply requires different machines and different mentalities. This is not always true, but like any industry, niches become relevant because it is difficult to be all things to all people.
The main difference between sheet metal and plate metal is weight! This might seem obvious to those in the industry but for outsiders it is often surprising to learn that handling a four-foot by ten-foot piece of 16 GA steel can be done by hand. It will weigh right around ninety pounds.
That same sized plate in .500 metal will weigh 817 pounds. We employ some strong workers but no human is strong enough to handle that much weight without special equipment to assist.
Just the handling portion alone between the two different weights is significant. The machines used to manufacture these types of metal are often different as well. Little machines must turn into big machines.
Little machines are quick, agile and swift; big machines are slow, powerful and sationary.
Because of all of these differences, as explained earlier, most shops focus on niches and build assets, skills and capacity around those niches.
AMF focuses on material and assembly weights that are five thousand pounds and under. We work with a combination of sheet and plate materials from 24 GA up to 1.00″ thick. As mentioned, the heavier-sized plates are items that we can make if they are small parts attached to lighter assemblies. A very simple example might be a small base plate 6.00″ by 6.0″ by .50″ thick attached to a square tube post. This would be a heavy plate combined with a light tube. The overall assembly is well under five thousand pounds and something we could easily fabricate at AMF.
Weight, gauge and thickness are all key factors for most fabrication shops. There are hundreds of fabrication rules that revolve around these factors—hole sizes, flange lengths for bending, welding wire, weld heat and weld passes are just a few—the list is extensive.
Decades of industry experience are necessary to truly master metal fabrication. All Metals Fabrication has a huge roster of employees and owners that have an enormous amount of experience. Metal fabrication is our thing.
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