Unless you are knowledgeable about aluminum processing and extrusion, it can be easy to make assumptions about aluminum round stock, also known as aluminum round bar, which are simply not accurate.
With many aluminum suppliers, the subtle or not so subtle differences between the round stock produced by different aluminum mills are easily overlooked. These suppliers may fill their inventory based on lowest price or current availability while the top aluminum supply companies are careful to only offer quality aluminum.
Tolerances in Diameter
Not all companies can manufacture aluminum round stock to the same degree of precision. The top quality companies can provide extremely tight tolerances that vary based on the dimension of the round rod from a small diameter of a quarter of an inch to up to and over nine inches in diameter with just a plus or minus of 0.054 inches.
These factors will all vary slightly based on the temper and the specific alloy. Typically, the larger the diameter of the rod the slightly higher the tolerance will be, but this is still minor and will fall within all standards even in demanding applications such as the aerospace industry.
Another factor to consider with any shape of extruded bar is the straightness over the length of the extrusion. In some aluminum alloys, this can be a very real concern during the extrusion process and the aging process.
Aluminum mills invest in specialized equipment and extruding systems that limit any twist or bend in the extrusion. This produces a superior aluminum round stock that is straight and produces cut after cut that is ready for immediate use in the application.
As with tolerances in diameter, there are also different tolerances in straightness based on the specific temper and alloy. The top suppliers stay well within these tolerances consistently, providing the aluminum suppliers and their end customers with quality products they can depend on.
Before making any purchases from an aluminum supplier, review the types of round stock they offer and the manufacturer’s tolerances. If you have any questions, make sure to call and talk to the supplier as you want to end up with aluminum round bar that is what you want and manufactured to the tolerances your project requires.