You also need to buy enough stuff from the guy in the Metal Workshop just to be offered the option to upgrade and then you need to have kept the 4 items (or at least more than 1 of them) you bought for Q#3. And then, hopefully, you can use the upgraded items to complete Q#3 after the Metal Shrine.
Bottom line is that if you complete Q#3 before getting the recipe for Q#6, you will be stuck unless you bought additional Q#3 items. Ahhhhh. Visios of FH quests are dancing in my head.

I have now missed several opportunities to complete quests. So why bother? Well, for me it is to document what is necessary to complete these in a future playthrough. But these convoluted quests can feel very frustrating.
