Crafting is done by doing /craft and then putting the numbers of the slots you are trying to combine.
For example if slots 1-4 where copper nuggets and slot 5 was a rusty pickaxe
"/craft 1 2 3 4 5"
would ask me for some gold plus the items and then give me a old copper pickaxe.
Recipes:
Pickaxes
"Old Rusty Pickaxe","250 Gold" = "Rusty Pickaxe"
"Rusty Pickaxe","6 Copper Nuggets","500 Gold" = "Old Copper Pickaxe"
"Old Copper Pickaxe","500 Gold" = "Copper Pickaxe"
"Copper Pickaxe","6 Iron Nuggets","750 Gold" = "Old Iron Pickaxe"
"Old Iron Pickaxe","750 Gold" = "Iron Pickaxe"
"Iron Pickaxe","6 Silver Nuggets","1000 Gold" = "Old Silver Pickaxe"
"Old Silver Pickaxe","1000 Gold" = "Silver Pickaxe"
"Silver Pickaxe","6 Gold Nuggets","1500 Gold" = "Old Gold Pickaxe"
"Old Gold Pickaxe","1500 Gold" = "Gold Pickaxe"
"Gold Pickaxe","6 Vlux Nuggets","2500 Gold" = "Vlux Pickaxe"
"Vlux Pickaxe","2500 Gold" = "Enhanced Vlux Pickaxe"
Helms
"Rusty Helm","6 Copper Nuggets","250 Gold" = "Copper Helm"
"Copper Helm","6 Iron Nuggets","500 Gold" = "Iron Helm"
"Iron Helm","6 Silver Nuggets","750 Gold" = "Silver Helm"
"Silver Helm","6 Gold Nuggets","1500 Gold" = "Gold Helm"
"Gold Helm","6 Vlux Nuggets","2500 Gold" = "Golden Vlux Helm"
Armors
"Rusty Armor","4 Copper Nuggets","250 Gold" = "Copper Armor"
"Copper Armor","4 Iron Nuggets","500 Gold" = "Iron Armor"
"Iron Armor","4 Silver Nuggets","750 Gold" = "Silver Armor"
"Silver Armor","4 Gold Nuggets","1500 Gold" = "Gold Armor"
"Gold Armor","4 Vlux Nuggets","2500 Gold" = "Golden Vlux Armor"
Rings
"Rusty Ring","4 Copper Nuggets","250 Gold" = "Copper Ring"
"Copper Armor","4 Iron Nuggets","500 Gold" = "Iron Ring"
"Iron Armor","4 Silver Nuggets","750 Gold" = "Silver Ring"
"Silver Armor","4 Gold Nuggets","1500 Gold" = "Gold Ring"
"Gold Armor","4 Vlux Nuggets","2500 Gold" = "Golden Vlux Ring"