A One Hand Sword is a Sword created with:
Heat the Ingots and put them on the anvil. Hold down 'Z' while looking at the Anvil and select 'Blades' from the radial menu. Hit the heated ingots until they turn into a sword blade. the change the design, keep hitting it until you are happy with it, then dip the blade in the oil and bring it to the workbench to connect to the guard and grip.