I love the super-rigidity found in aluminum squares and straight-edge rules. I've purchased cold rolled steel flat bars that flex far easier. In fact, when applying force against the thin edge of these aluminum squares and rules, I cannot get them to flex at all.

How do they get the aluminum to be this rigid and strong? What kind of aluminum is this? It would be great for a project I am currently working on.

  • You're really working hard on this MDF door, aren't you ;)
    – Hank
    Apr 26, 2013 at 4:51
  • You've been paying attention. Yes, I am, and it's to the point of insane determination. There is a way to reinforce this door in a low-profile fashion and I am going to find it if I have to die trying. Apr 26, 2013 at 10:21
  • My local big box hardware store sells extruded aluminum in a variety of shapes. See if they have something that works for you.
    – Craig
    Apr 26, 2013 at 14:42

2 Answers 2


Aluminum is made of aluminum - processed from rocks. This is actually a great "How It's Made" Episode. There is very little that really changes with most aluminum that you buy other than size and shape. I am sure there are slight differences in strength due to tempering processes and coating but this is usually minimal. If some aluminum is a lot "softer" than others it is probably because it is not pure aluminum.

Steel is an alloy. There are literally thousands of different steel mixtures. Depending on how they want the steel to turn out they add (or take out) different minerals - including aluminum sometimes. Steel is basically a mostly iron alloy and a lot of its properties are subject to the amount of carbon. I think if the carbon amount hits 2-3% steel becomes very rigid but also is very brittle. A ruler would not have a high carbon % in the alloy because it would need to be very flexible (relatively).

Steel for the most part is "stronger" than aluminum but it depends on the alloy composition and the tempering process (which has a stronger affect than it does on aluminum). The strongest steel is much stronger than strongest aluminum.

  • Aluminum in its natural state found in the earth is Bauxite ore. The ore contains a percentage of aluminum that is processed out, melted and formed into ingots. Aluminum has a very high melting temperature and is technically not a true metal, it is an element known as a metalloid, meaning it has properties of both metals and non-metals. Apr 26, 2013 at 22:38
  • 3
    This answer implies that there is only one kind of aluminum that can be bought when in fact there are a number of widely used alloys. As with steels, the heat treatments that are done on many of these aluminum alloys significantly modify their properties. Finally these alloys are stronger than pure aluminum, not softer.
    – JayL
    Apr 27, 2013 at 5:22
  • @JayL... then it isn't aluminum it is an aluminum alloy. I was just trying to answer the question, not expand on aluminum alloys available. And still the best steel alloys outperform the best aluminum alloys...
    – DMoore
    Apr 27, 2013 at 18:35
  • 2
    @DMoore : tools made of aluminum alloys are still typically sold as 'aluminum', and there are lots of different types of alumninum alloys, as you have to consider not only the composition but also the way it's worked (eg, 1050-H14 or 6061-T6)
    – Joe
    Apr 29, 2013 at 22:41

When you buy 'aluminum' extrusions or find a tool made of 'aluminum' at the hardware store, you can be virtually certain that it is not pure aluminum but is instead an aluminum alloy. Pure aluminum is not very strong by itself. However, there are a number of different aluminum alloys for different applications, many of which are quite strong. Some of these can be further modified in useful ways using heat treatments. You can read about some of the common aluminum alloys here Online Metals Aluminum Guide (no affiliation other than past customer). The 6000 series alloys are commonly used for extrusions and other structural components where strength is important but cost is also a factor.

If you are looking for a similar material it may be useful to find a specialty metal supplier near you as they would have a much wider selection of shapes and sizes than the big box store, and you can probably get some advice on what alloy is appropriate for your project. Also they will cut it to your specifications for a small charge. I have had good luck doing this even when buying small quantities.

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service and acknowledge that you have read and understand our privacy policy and code of conduct.

Not the answer you're looking for? Browse other questions tagged or ask your own question.