The above 6 items are the only items that can be smelted all other Dwemer items (cups, plates, levers, cogs, gears, gyros, knife etc.) are pretty much useless, don't even bother. He'll want you to go and bring him TEN Dwemer Cog's, but he WON'T tell you what he's going to use them for. They are well known for their skill and revolutionary developments in technology, engineering, crafting methods, metalwork, stonework, architecture, city-planning, science, mathematics, magic, and the academic arts. Additionally, the cogs can be difficult to find once collected. The Dwemer were an advanced race and civilization, in many respects far ahead of the other races and civilizations of their time. The quest does not include any accompanying quest markers. Because the Dragonborn must collect ten Dwemer cogs at the various ruins across Skyrim, the first stage of this quest can often drive players away. Mzulft itself also contains one of the biggest hoards of Dwemer artifacts in Skyrim. Many players don’t want to take it on or even finish it. The above 3 items give you a ratio of 1.5 ingots per (kilo?) These have literally 10x better weight/ingots ratio than the other 3 possible smeltable items but I'll list them here anyway. Some of the items like Dwemer Bowls, Cogs, Dishes, Gears. So if someone told you to collect 'Dwarven Cogs', they really meant for you to collect 'Dwemer Cogs', found almost exclusively in the assorted Dwarven ruins. If you're wanting to smelt for dwarven ingots, there are really only 3 items worth picking up based on their weight/ingots ratio. So 'Dwarf' is to 'Dwemer' just the same as 'Dark Elf' is to 'Dunmer' or 'Wood Elf' is to 'Bosmer'.

Skyrim dwemer cog