a quest and
60 smithing for a fully working script(easier)
less than 60 smithing requires some teleporting around'
http://runescape.wikia.com/wiki/Blast_furnaceThe Reason why blast furnace is amazing is
A. The dwarf in blast furnace can unnote ores(up to mith) Charges money, but B makes it a cheaper alternative
B. Everything takes half the coal to smith so 1 iron + 1 coal = 1 steel, 1 mith + 2 coal = 1 mith, etc,etc
C. Making stackable arrowheads,bolts means you can stay down there as long as your ores hold out thanks to A
Drawbacks of blast furnace
A. It is a collaboration game just like fishing trawler(as in if you don't help your ores will take longer to come out)
B. People often point out the leachers(people not doing anything but putting ore in and smithing bars) and heckle them
C. You are surrounded by people.