You might want to bend it instead over a piece of steel the same thickness as the tang to save the tang from any risk of damage. This is especially true if the blade is a true antique. This will, if nothing else, reduce the risk of work hardening the blade in this critical area. A polished 1 or 2 lb hammer is used to tap the strip until it closely conforms to the shape of the blade. During hammering the various ridges of the habaki are defined.
Great care is taken to never strike the blade.
If the strip work hardens it is annealed and the proceedure is continued until a good fit is achieved. Work hardening is felt as a springyness in the strip while it is being worked. The hammer should hit with a dead feel. When the strip conforms closely to the blade a small wedge is inserted between the gap formed by the open end and the assembly is soldered shut. If the wedge is correctly dimensioned and positioned properly the habaki should fit in place.