Aluminum Extrusion and Fabrication: Temper and Tolerance 101

The more you know about aluminum extrusion and fabrication, the difference between various alloys, and the methods used to create products in aluminum fabrication shops, the better you will be able to use it to your advantage. There are two important properties of aluminum that can be kind of confusing, however, once you dig into how they relate to the finished standard or custom aluminum extrusion, it makes a lot of sense. Today we will be discussing temper and tolerance, as well as how you can use this knowledge to your benefit when you extrude aluminum alloys for industry solutions.

What is Temper?
When you look at the different aspects of each type of aluminum alloy, you will see a notation next to it, such as T1 or T6. That notation refers to the temper grading of each alloy, which provides information regarding its behavior during the extrusion and fabrication process. When you are looking to purchase extruded aluminum from aluminum fabrication shops, it pays to know which range of temper would be best suited to your particular needs. The temper for aluminum alloys in the 1000-series can be different than the temper for aluminum alloys in the 6000-series. However, the most common series used to extrude aluminum alloys is 1000, 6000, and 7000-series. At Silver City Aluminum, we use the 6000-series for all of our standard and custom aluminum extrusion.

The 6000-series is alloyed with magnesium and silicon, which makes it stronger, while still allowing for quality extrusion and fabrication. There are other series that offer different benefits for extrusion. However, there are still other types of alloys that are not good candidates for the extrusion process. When you look at a list of alloy options available at most aluminum fabrication shops, you will see the temper grading next to each type. There are five letters used for this designation, including F, H, O, T and W. However, you will see T most often as it indicates that some form of heat treatment was given to increase the strength of the metal. The most common grading seen in the 6000-series is T4 and T6.

What is Tensile Strength?
For each type of aluminum alloy, you will also see additional information that follows the temper grading, which includes tensile strength or ksi. Ksi stands for kilo-pounds per square inch, which is the way that tensile strength is measured. The chart will usually list the ultimate minimum and maximum tensile strength, followed by the minimum and maximum yield. The ultimate tensile strength (UTS), which can also be noted simply as TS or tensile strength, is defined as the capacity of a material to be able to withstand loads without breaking or being pulled apart. The type of load measured with tensile strength tends to cause the material to stretch or elongate. Another form of measurement, compressive strength (CS) measures the resistance of a material that is compressed or pushed together.

In a laboratory or industrial setting, ultimate tensile strength is measured according to the maximum amount of stress that a material can withstand before it breaks. The tensile strength of a 6000-series T4 would be a minimum 19.0 ksi with a 10.0 ksi minimum yield. The tensile strength of a 6000-series T6, such as 6063-T6, would be a minimum of 30.0 ksi and a minimum 25.0 ksi yield. You can see a complete chart which notes all of the options to extrude aluminum alloys at Silver City Aluminum on our website under the “Engineering” category listing. However, your best bet is to work with our engineers to determine the best possible alloy for your particular extrusion and fabrication needs.

What is Tolerance?
Before you can understand what the term tolerance means in aluminum fabrication shops, you need to know that there is always a degree of bow and twist as the extruded aluminum alloys leave the die or profile to cool. However, there are industry standards for the maximum allowable distortion, which is known as tolerance, for each type of alloy used in standard and custom aluminum extrusion. In general, the “worst case” scenario for any type of extrusion and fabrication would be 0.5 degrees per foot of “twist” and 0.125″ per foot of “straightness.”

There can also be a slight variation in the angles of some extruded features. However, this should not exceed a measurement of +/- 2 degrees. Tighter tolerances may be achieved for custom aluminum extrusion orders, so make sure to discuss this with the engineer during the design and development phase. A PowerPoint presentation on the topic of tolerance is available on the Silver City Aluminum website under the “Engineering” section’s “Design Tips” area. All of the information provided here can be extremely helpful to clients who are designing profiles for use in extrusion and fabrication.

Contact Silver City Aluminum
If you are interested in designing your custom aluminum extrusion profile or if you just want more information on the services available at our one-stop aluminum fabrication shop, give us a call at 508-542-7200. You can also use our online order form to get the process started. We take pride in the work that we do, and our team of engineers and technicians work closely with each and every client to extrude aluminum alloys that will meet or exceed their expectations. Whether you need standard or custom solutions, you can count on Silver City Aluminum to help you achieve your goals.