I'm unsure exactly how they're supposed to work, but here's the story.

I feel like I went way overboard with my first character and smithing / enchanting (uber powerful weapons and armor). So for this play I've decided to do the opposite and keep it simple, without spamming the skills (I want to level my character more organically) or going any further than steel/magic and enhanced/fire on the trees, respectively.

My smithing is at 25, and I improved my weapon (Queen Freydis's Sword) at a grinding wheel. Then later I used a Blacksmith Potion I bought which is supposed to improve by 30%, and tried to improve my weapon again, but it had no effect and the wheel wouldn't even let me try. So was it a glitch, or is there some sort of percentage mechanic at work that I'm unaware of?

Basically I'm hoping to improve my weapons and armor as much as I can during play using only blacksmith enhancing items and potions, and calling it good enough, rather than indirectly inflate my character level with a lot of smithing and enchanting skill leveling.

Any advice would be appreciated...

The potions don't allow you to upgrade them to better stats right after a previous upgrade. If the potion ups your skill to the proper level, let's say from 25 to 30, it will only allow you to make a better weapon if smithing level 30 includes a higher upgrade level. So if level 25 allows for epic weapons, 30 would have to allow for flawless or legendary for you to see any difference.

I hope that makes sense it's kind of difficult to explain.

It increases your smithing skill by 30%, not your weapon.

Oh o.k., thank you.

Does anyone know of an official skill level scale anywhere for upgrading, like '20 = Fine, 40 = Flawless', etc.? I made those up as examples...

Without perks...

Fine 14
Superior 31
Exquisite 65
Flawless 100
Epic 134
Legendary 168

With perks...

Fine 14
Superior 22
Exquisite 40
Flawless 57
Epic 74
Legendary 91

_{If this list is true, then why can't I upgrade leather to legendary without enchanted jewelry and potions even though my smithing is at 100?}

check here: http://www.uesp.net/wiki/Skyrim:Smithing#Item_Quality

Thanks. I just got that out of the book real quick. It's off obviously... Trust wiki. Sorry cobrasno1, check the wiki, and not the guide book.

Because Leather has no associated perk to HALF the needed skill and thus you need 168 Smithing to make LEGENDARY Leather. Same with Hide and Fur items.

I think they screwed up the Smithing Tree (or changed it last minute) as there are several questionably located and missing perks.

IDK if this helps, but I have 4 items I've enchanted to Fortify Smithing +25% and I can make Forsworn Legendary with my Smithing at 100 and all perks in the constellation. I assume the same would be true for leather and fur since Forsworn seems to be fur or a hybrid of leather and fur.

Yeah, they should lump leather and fur into "Advanced Armors" for Thief and Assassin types. I know it's not really "advanced" per se, but it fits there better than Elven or Glass.