Why can't I make any Tinkers Construct parts with iron?

I was trying to build an iron hatchet today, but suddenly I noticed I couldn't make any part with iron! Any other material like cobblestone or wood works, but not Iron. It just doesn't show anything on the right.

I think it has something to do with the new Hexxit Update. A few days ago I had made an iron Mattock, but after updating yesterday I can't. You can actually see the mattock there in the hotbar.

Am I the only one? Is it a bug? How do I fix it?

Solution 1:

Looking at the Minecraft Forum post for Tinkers Construct, and this is at the top of the post:

Metal parts, including iron, have to be made with metal casts and the Smeltery. Casts are crafted by pouring Aluminum Brass/Gold on a tool part.