According to HubPages
Billet means a solid chunk of aluminum. According to HubPages the part is machined out of
happy a single block of aluminum such as bar stock as it was produced at the foundry.
Such parts are superior in strength as they have a much stronger crystalline structure, or "grain", and don't have the stresses of a welded part due to excessive heating and cooling.
The structure of the grain has not been disrupted because material has only been cut away from the original piece and no excessive heat has been created.
