My one idea, I think would work, but it certainly lacks "finess";
If you don't mind it being done over several exchanges, instead of 1, I'd do it like this:
Every object has a quality and stress track based on that quality. Objects resist attacks with their quality and some may have an armor rating.
Why not "attack" the object with a spell - like any evocation attack where the power equals the weapon rating. The attack doesn't actually do damage, it just represents reshaping the item, although in reshaping the item, I guess you're, in effect, damaging it. Do stress to the object and give it consequences. The consequences are in line with shaping the object into something else. When you finally inflict an Extreme concequence...or "take it out" it's a new item.
A pipe into a knife would have mild consequence of Flat, a moderate of Sharpened etc...
I know that objects don't usually get consequences, but his magic would specialize in this kind of thing - it's purpose is to create consequenses in items to use for crafting.
So, for shaping most objects outside of combat, you wouldn't even roll (because that would be tedious and an object can't attack back). You'd say it takes 20 minutes and it's done. Then do a quick craft roll to see how well it worked.
But say you want to turn your enemy's sword into a useless blunt object during combat, you could, but it would take multiple exchanges and the higher the quality the sword, the harder it will be.
To actually craft it into something else, there'd always be a craft role associated with it and the difficulty would be based on how wildly different the new object is from the old one. Trying to increase the quality of the item would also increase the difficulty. On the up-side, you could tag all the items consequences for your craft roll.
EDIT: maybe you would roll outside of combat, because everytime you cast a spell you take mental stress and possible consequences. So your metal worker might not be able to do an item in one sitting. He could still do it WAY faster than using any mundane forging techniques.