According to UOguide, and my memory, smelting a crafted metal item when you are a smith should give you back half the ingots needed to craft the item.
If I remember correctly, smelting looted or bought items will yield only 1 ingot when smelted.
However, no matter what item I smelt with my smith, especially the stuff I crafted to train my skill, returns only 1 ingot a piece, even if the items requires more than 2-3 ingots to craft.
I don't think this is intended. I did not test leather and cloth cut by scissors for tailoring.
I think here is also has to do with mining. Having mining will make you more proficient at smelting metal items to ingots.