One way to craft a Tool Binding is with a Part Builder. Put a unit of the desired material and a Tool Binding Pattern in the Part Builder. Tool Bindings have a material cost of 0.5.
The other way to craft them is with the Smeltery. Fill the appropriate Cast with the liquid metal and let it cool.
Various Tinkers' Construct tool parts can be found in the chests in a house in most villages.
Tool binding is a piece of a tool used in combination with the Tool Rod and Pickaxe Head to craft a pickaxe in Tinkers' Construct. Tool bindings do not contribute to the tool's durability or mining speed. However, a binding can contribute abilities, such as additional modifiers, Reinforced, or Stonebound.