How do you forge a katana?

Answer 1

Modern katanas can be made as any other swords are made as long as proper materials are selected, and care is given to the correct harmonic/dynamic balancing and hilt/blade proportions along with proper heat treatment.

Traditionally made katanas are forged and get their shape from the way they are heat treated. A special mixture of clay is applied to one side which results in a differential heat treatment-this causes the spine to cool more slowly then the edge making it curve upwards. They was made this way so they could be hard and tough at the same time-this heat treatment isn't important with modern steels although it is still done for the cosmetic and traditon purposes. (Cosmetic as in that it results in a hamon line) The hamon line is that curvy line that you see near a katana's edge-fakes have this line laser etched. Real swords have this line made as a result from the clay treatment and chemical etching.

With all of that being said-making swords is a very involved and complex trade and should only be done after you have several years worth of experience from making smaller blades. Design the blade, Select the materials, Layout the design on the steel, forge/grind/cut it to rough profile, refine it to final profile size by the use of files or a grinder, start the initial grinds, start the first finishing processes, heat treat it, complete the finishing steps, start work on the handle, attach handle, finish/polish handle, test proportions and balance, redo if necessary, start/finish master grinds, retest,redo if needed, add maker's mark. I only make knives so some of the above steps might be out of order/incorrect for swords.