Purchasing aluminum

Why does it need to be aluminum?

I make a lot of spacers and bearings with acetal; very nice to machine, relatively light weight.

Aluminum or Mag/alloy was just my thought of following suit with current prosthetic practice. Now that you've mentioned it, any materiel with light weight, easy machinability and able to withstand the compressive load of walking would work fine and probably be more suited to my needs -- Now that you've given it a name can you share a source? (I promise I won't ask you to machine it as well)!

McMaster Carr has a pretty good selection of different shapes. They also give a fairly good material property description. The acetal should handle and absorb the load well as long as it has a good even bearing contact.

eBay. I needed a small piece of titanium bar stock for a pair of rings I was going to machine, and I found one just the right size for an outstanding price. McMaster's smallest size was still too large and way too much money.

--edit--

Actually, if you give me the dimensions you are looking for, I might be able to look through our scrap bin at work and just send the darn thing to ya.

You don't mention the size or quantity of material that you need. Although we sub-contract all of our machining, we sometimes need to make the odd item in-house. We can often find the material we need from the local DIY or model supply shop.

You could also try junkyards/scrapyards (metal recycling facilities). They usually separate the different types of metal and sell it very cheap. I have found all kinds of aluminum bars/plates, linear bearings and ballscrews, needed for a machine I was building, at a fraction of what I would have paid new.

Just a thought...

Suppliers to the hobby machinists may have what you need. Try www.speedymetals.com , www.asapsource.com , www.metalsexpress.net or e-mail metalsource@metalsource.com. I have not used any of these sources, good luck