> inquire about aluminium. I guess its more expensive right??
When you build a million, maybe a thousand, steel may be significantly cheaper. But very hard work unless the part is super-simple (building frame) or you set-up dedicated punches.
When you need a non-trivial shape/holes/bends, Aluminum can be MUCH cheaper for the first one or a dozen because it can be shaped by hand or small-power tools.
Al $1.10/lb
Steel $0.50/lb
In the same thickness, the price is not very different, because Al is a third the density of iron (or steel). Today, a foot of 1/8" stuff is cheaper in Al than in steel.
However in a direct pull, you can use thinner steel to get your strength.
However again, we don't direct-pull our gear, we accidentally bend it.
In bending, for a given material, twice as thick is FOUR times stronger. And 8 times stiffer. So even if Aluminum were half the strength of steel (a very fuzzy area), twice the thickness of Al will be as strong as steel (and stiffer).
How much stuff can be in this box? 5 pounds of steel? $2.50? Surely the bending and work will be 20 times more expensive on a small run. Twice as thick Aluminum would be 2/3rd the weight, 3 pounds, $3.30. And the working will be the same or cheaper in a real metal shop (same number of operations, but each operation is easier and less wear on the drill). And Al is much less intimidating to the average DIY worker: it cuts with wood-work tools.
Basically when you can get the cost of the work down below the cost of the material, then you worry about material cost. If you make a million cars, with a panel like a 26U, you spend a month cutting ONE stamper to blank the 17"x8" outline, the top/bottom lips, the holes, all in one blow. Then you WHANK WHANK WHANK WHANK 3,000 per hour, instead of 3/hour using general shop-work. In a few hours your expensive stamper has paid for itself, and the per-part cost comes down to the raw metal cost. Knowing this, you re-design the shape with more ribs to use thinner steel instead of thick aluminum.
Note that nearly all car-engines have switched to aluminum. Partly because weight matters in a car. But also because a hi-revving engine needs a stiff structure. At the same weight Al can be 3X thicker and _9X_ stiffer. Or for the same cost (today's price), 1.5X thicker and 2.2X stiffer (and half the dead weight). (Also because even with costly tooling, it is hard to get intricate shapes in iron, easier in alloy. Ford bought Lincoln because Lincoln was about to cast a Vee engine near as cheap as a straight. Nearly all aftermarket Chevy heads are alloy because only one non-Detroit company has mastered the trick of casting ports and jackets in iron.)
