Which kind of Aluminum is a good choice

[D_Price]

Originally Posted by nuclearnerd

Yeah, I'm still *really* surprised at the things FRC people use 7075 for. It's aluminum trying to be steel - same strength as (mild) steel, but way less stiffness, way less toughness and way less hardness. (The latter can sorta be overcome with hard anodizing, as long as you don't actually stress the coating too much.)

7075 could maybe find use in highly stressed structural plates, where you want to save weight on a big piece. But for small shafts & gears, don't be silly - just use steel!

I agree. Just splurge a little more on steel as it will save you a ton of headaches

[nuclearnerd]

Also note welding aluminum is more difficult than steel, and 7075 can't be welded at all. Welding will reduce the strength of aluminum in the heat affected zone significantly. 6065 can be heat treated after welding to restore its strength, but you'd have to find an oven big enough to fit your whole weldment. It's easier to just design the part with a large safety margin, but doing so will eat into the weight advantage of aluminum.
http://www.lincolnelectric.com/en-ca...qs-detail.aspx

[nuclearnerd]

One more thought: While 6061-T6 is the arguable the best all-round alloy to use because of its strength (276 MPa at yield), 6063-T5 is far more common and cheaper at shops like metalsupermarkets.com. Be aware that 6063-T5 is only half the strength (145 MPa) of 6061-T6.

[Madison]

It might be worth noting that the question is, itself, coming from China.

[Chris Endres]

Just another note:

6061 is used best for flat parts.

5052 is great to bend.

It also depends on the bend radius, but for a rule of thumb, bent = 5052, straight = 6061.

For alloys, just make sure you do your research, we use 6061-T6 and 5052-H32.

Here's a video showing what happens when you make bents parts out of 6061 vs 5052.

https://www.youtube.com/watch?v=KgeP__CSiSw

[Richard Wallace]

FWIW, my team has had no problems with shafts made from Thunderhex. We love the stuff because it fits both hex bearings and hex broached holes perfectly, eliminating the "file to fit" step. It also comes with a 0.2 inch center hole that works well for clearance to #10 screws and for tapping 1/4-20 threads. And it machines very easily, leaving beautiful diameter and face cuts with ordinary HSS tools.

It is 7075. I think Paul Copioli or one of his technical staff could provide some background on how they selected a supplier, and what tests were performed. I only know we have never bent or broken it.

[IndySam]

We use 3003 for our bent parts and 6061 for flat parts that need the extra strength. We only use 7075 when purchased in shaft form from AM or Vex.

We get most of our aluminum provided by our amazing sponsor Waterjet Cutting of Indiana.