FASA Games, Inc.

No.

Let me clarify by way of example.

A Weaponsmith could use Forge Weapon to increase the Damage Step of Purifier. He could not use his Circle 5 ability to add Karma to a damage test made while using Purifier as he did not make Purifier. Forge Weapon or similar enhancement talents do not change who made the weapon.

If a Weaponsmith creates a thread weapon (through the enchanting process), then he can use the Circle 5 ability on damage tests for that weapon. He can also use Forge Weapon to increase its damage step.

(Edit: Etherial covers it as well -- though it does not allow a Weaponsmith to spend karma on a damage test for a weapon he made that somebody else is using.)