Which kind of Aluminum is a good choice

[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!