The radial menu doesn't work. I can switch to hammer head after I select blades. Restarted the game just in case it was a glitch, nope, it's defo a bug.
The radial menu detects how many ingots are on the anvil to determine which options are available. For instance, hammers do not have a one ingot hammer head, and as such will not be selectable with only one ingot on the anvil.
