Im attempting to discover if there is a bug with some crafting enchants stacking. Specifically, Smithing.

I run the PC version and did some testing, because the bonuses did not seem to have the expected effect.

I created 3 items, a ring, gloves, and armor that each give a 16% bonus to the smithing skill, and then tried using the grindstone to improve the damage of an elven bow. The base damage went from 31 points to 33 points, without using any of my enchantments. When I equipped the 3 smithing enchant items, I saw no change. Note that I have only the base 15 points in smithing. If each of the 3 pieces was giving me a 16% increase to the base improvement of 2 points, cumulative, that would be a total of 48% improvement, and I would expect slightly less than 1 point improvement to the improved item, correct? So it must be rounded down, therefore I saw no improvement. Which is fine. However, to get bigger numbers to play with, I gave myself a skill of 100 in smithing, and tested the enchants again.

This time, the base damage without enchantments was 46 for the bow (base 31, + 15 = 46). When I used my 3 smithing enchant items, I got a final damage of 50 points.

So at 100 smithing with no enchants, 15 bonus; with 3 enchanted items, 19. 4 points difference. Now it would seem to me that if I have 3 items giving a cumulative bonus of 48% applied to 15, I should be getting 7 bonus points rounded down, not 4 (.48 x 15 = 7.2).

Am I doing something wrong? Is my math messed up? Thanks for your patience in answering this. I also so now effect to enchanting using potions, so was wondering if that was bad too.

Different sources do indeed stack, but not infinitely. There is a cap.

If the cap is that low, that 3 relatively minor enchanting bonuses dont get thier full value, it would seem to be pointless to raise enchanting up very high. Which would be disappointing.

I think skill effectiveness tapers off a lot if you go over 100 (Even without the ones that glitch and go negative).

Smithing works in tiers too. Steel Sword (Flawless)s are all the same damage, whether you just hit the required skill for it, or are one point short of making it Epic.

the smithing upgrades are pretty big steps. You can look it up if you want, but it's like 25 and the next is 60, and the next is 100 and then over 100 (via enchant and alchemy boosts). You need 162 Smithing to get the highest upgrade (Legendary?) without the Smithing perk.