Okay so check this out:
Take 1 tin, 3 copper, and 1 iron (and 6 rubber and 4 glass, but those are all super-easy renewable with cobblestone and farming)
That's enough to make a liquid heat exchanger.
Place the exchanger and then mine it with a -pickaxe- and not a wrench.
Turns into a basic machine casing... which you can then just craft straight up into 8 iron ingots. So you turn 3 copper and 1 tin into 7 iron (Keep one iron ingot on hand so you can do this again 
)
If you wanna go a step farther, you could even put the iron in a blast furnace and reprocess the slag in a thermal centrifuge. 2 cycles of this will give you 14 iron, giving you 14 slag, giving you 14 small gold dust and 70 coal dust. You can then take flint and obsidian, and get a diamond. So now you've turned 6 copper and 2 tin into 14 refined iron, a diamond, a gold ingot, and 20 coal dust and 5 small gold dust in change.
Hell, technically you're only using 2/3'rds of a tin ingot each time, since you get an extra fluid cell each time. Do it 3 times, and you only need 9 copper and 2 tin.
Innnteresting, mm?
