Small Silver Ingot, Small Gold Ingot and Small Platinum Ingot are used in variety of tradeskill processes, so it's always good to collect a few of them. But if you don't know how, obtaining them can be problematic. In their raw form they drop of regular mobs, mission and dyna bosses and are found in those little brown boxes in missions. But for everyday use, droprates are too low. Unfortunately, for QL 200+ this is the only way to obtain them (so you might want to save them for few processes that actually benefit from high QL, like SL and AI rings).
Regular Joe, Jane and...er..neuter can get Small Ingots from little tradeskills, here is what you will need:
The initial process involves x3.2 in Mechanical Engineering Skill when dealing with Gold, x2.75 in Mechanical Engineering Skill when dealing with Silver both based on the QL of the material. Basically anything with gold, silver, ring or bracer in name can be used, as long as found on RK and didn't drop from a special mob.
Right, so this should help you stock up on Small Ingots. Since no tradeskill involves non-processed Ingot, we might as well melt them down. For that pick up your Personal Furnace. Melting down metal will take x3 for Silver, x3.4 for Gold and x3.8 for Platinum in Mechanical Engineering Skill based on the QL of the Ingot.