For GURPS 3e there is also GURPS Architecture by Matt Riggsby
http://www.mindspring.com/~wombat3/archt.html Just keep in mind that it is 20 years old.
Also, realistic low-tech crafting of anything as complicated as a sword tends to involve teams of specialists. The guy who forges the blade is not the one who hilts it or polishes it or gilds it or makes the scabbard or carries it and 143 of its closest friends to the nearest port. So in many games, you may not want to be too realistic.