When shipped from the manufacturer, most bicycles have a rear derailleur hanger made from recycled aluminum (drop-forged or machined). However, replaceable rear derailleur hangers provided by derailleurhanger.com are machined using aircraft-grade 6061 aluminum (with a few exceptions; some initial hangers we stock may use other types of aluminum before being machined from 6061 T651 aluminum). At derailleurhanger.com we sell hangers that are machined from aircraft-grade aluminum because that type of hanger is far superior to derailleur hangers that are made using recycled aluminum.
Please keep in mind that it is still important that a replaceable rear derailleur hanger breaks under severe load so that the frame of the bike is not damaged. That is why we do not make replaceable rear derailleur hangers from titanium, as the titanium hanger will most likely not break under severe loads, resulting in a bent or broken bike frame. However, it is also important that a replaceable rear derailleur hanger not break under standard loads, such as an aggressive pedal stroke or repeated strain under normal loads. The role and origins of the replaceable rear derailleur hanger was the subject of our 9 February 2018 blog post, which you can find here.
Let’s dive into a bit of background regarding the metal and the manufacturing process used in creating replaceable rear derailleur hangers, starting first with the metal…aircraft-grade 6061 aluminum versus recycled aluminum.
Recycled aluminum is just that – aluminum that has been recycled from used cans or other aluminum products. Therefore, depending on the process used in refining the recycled aluminum, any products made from recycled aluminum will include various degrees of impurities contained in the recycled materials. There are also no industry standards associated with “recycled aluminum.”
Aircraft-grade 6061 aluminum, which is used to manufacture replaceable rear derailleur hangers sold on derailleurhanger.com, must conform to industry standards, and during the manufacturing of 6061 aluminum, sample lots are tested to ensure compliance with those standards. Aircraft-grade 6061 aluminum is actually an alloy containing other elements in specific quantity. Those elements were selected and incorporated to ensure optimum strength, flexibility and durability of the metal. Pure aluminum is too soft and weak to withstand the strains required in aircraft, and in bicycle frames and components or in a plethora of other products.
Let’s now shift our attention to the process used to create these three categories of hangers – drop-forged, cast, or machined hangers.
Drop-forging is a process whereby a hardened template is dropped with great force or pressure onto a piece of metal, and the template and the pressure forces the metal to take on the desired shape or geometry. For example, when you were a child you may have had templates that you could use with clay or Play-doh to create particular shapes or figures. Similarly, to create drop-forged derailleur hangers, a template is dropped with great force onto an ingot or piece of recycled aluminum to create the derailleur hanger. Recycled aluminum is used because it has lower strength than aircraft-grade aluminum, and therefore the recycled aluminum will more easily take on the desired shape of the template in the drop-forge.
Casting is a process whereby the recycled aluminum is melted and poured into a cast in the desired shape of the rear derailleur hanger. The cast derailleur hanger cools, is removed from the cast, and then is smoothed before being sold. However, casting can only be used for hangers that have a flat surface on one side of the hanger. Many rear derailleur hangers used on bikes today have complex geometries on both primary sides of the hanger, and therefore casting cannot be used to create those hangers.
With machining (sometimes called “CNC” for “computer numerical control”), a highly specialized machine is used to literally carve the derailleur hanger from a refined unit of aluminum. Hardened bits (similar to drill bits) are used to carve and shave the aluminum to generate the hanger so that it has the required three-dimensional geometry.
In summary, at derailleurhanger.com we purposely sell replaceable rear derailleur hangers machined using aircraft-grade 6061 aluminum, not hangers that have been drop-forged, cast or machined using recycled aluminum. Under normal loads our hangers will far outlast replaceable rear derailleur hangers made from recycled aluminum, but will bend or break just as they are supposed to under severe loads, such as falls or crashes.
We hope this blog post has been informative and useful, providing some background regarding why derailleurhanger.com sells replaceable derailleur hangers machined using aircraft-grade aluminum.
Our goal is to provide the best customer service in the industry so that our customers can quickly find, purchase and receive the correct replaceable rear derailleur hanger for your bike, and you can quickly be back on your bike. We hope this blog post, and the “1-2-3” process and other information available on our website, does just that. Again, if you ever need any assistance, please click on the “Contact” link on our website and we will respond quickly and provide assistance.
As always…please let us at derailleurhanger.com know if we can assist you in any way. Happy riding!