As the picture saids, Crafting is the main objective of this game.
It is how you create swords, which in turn is how you finish quests, complete collections, make money, et cetra.
There is no magic temperature or quality number that will guarantee you get the sword you want. Luck plays the biggest role. You can though, increase your chances by raising your Mastery, raising your Crafting Points(CP), and buying the Trophy for the respective Craft you are making.