If you craft an 'artifact' quality item it receives random bonuses just like 'named' items. This also applies to Emerald Amulets. You can find which weapons are 'artifacts' on the wiki. I just crafted a Flail of Pleiades that gave me piercing resistance, counter and sneakiness. This really should be spelled out in-game somehow. The weapon types also need to be balanced - Maces are the only weapons that have high-level artifact crafting recipes. *edited for clarification*
Heh, yeah, I have crafted that same mace and it came with 2 additional Aethereal damage(on top of what its meant to have), 4 holiness damage, 2 toxic resistance, 1 Voltaic resistance, and I think it was +2 sight range. I am almost certain there was one more bonus, but I can't recall what it was at all. Also, I don't know if it has do with being artifact class. I seem to recall random crafts getting perks from time to time once they have been made at max crafting. I could be wrong, though. Are you just assuming or have you tested it/seen developer comments that support that?
Eh. There are a lot of items that the wiki lists as an artifact, and I've found a lot with no random stats. My last character found three Toque of Kanadas on the same floor, and all three just had base stats. The Poncho With No Name is a very common item, and I've never seen any with random stats.
Yeah, sorry, I meant "just like 'named' items" not "found artifacts". Artifacts that you find behave just like normal items. @Kaoy I've never had random attributes on normal crafted items.
Okay, I tested it with some quick modding. Wooden Sword to Wooden Sword recipe 50x got me nothing at smithing 5. Same recipe but with Wooden Sword made into an artifact with artifact quality 1, it gave me random stats every time at smithing 1. So I guess that means that the following crafted items will get random stats: Omnipotent Pork Sword Clockwork Chainaxe Magma Mace Flail of Pleiades Edit - Oh, oops. I didn't even make it an artifact. I just added artifact quality 1. Accidentally made the rusty sword an artifact.