Luck becomes 100% fail at different levels, based on the crafting skill (and their caps).
The chance to fail is 30%+(current luck/2) -1%((skill-100)/10)
So, for Carpentry, Tinkering and Fletching, that is 100% at 140 luck, before factoring in the other fail chances from the other properties being changed (resists, lower requirements, durability).
For Tailor, it hits 100% fail at 142 luck, because it can't go over 120.
Smiths, if 120 skill and holding a +60 ASH, hit 100% fail at 148 luck.
Note that the max luck from Reforging & dungeon loot is 150.
Even those numbers are misleading. IIRC, the formula checks each change, and if any ONE property fails, they all fail. So if you started with a armor metal item that was 10/10/10/10/10 resists, and enhanced with gold, you'd have a (70%)^5 * 80% (LReq base, if the property isn't already present) = 16.807% * 80% = 13.4456% IF THE ITEM STARTED AT ZERO LUCK.
So, if that hypothetical item was 140 luck, instead of 0, at 120 Smith (no ASH), the chance of success would be 0.134456%, or about 1 in 750 chance of success, with about a 90% chance of breakage on a failure (breaking chance is about 10% less than the failure chance). This is because 120 Smith is 1% success at 140 luck.
Here's the breakdown from the enhancing page
- All Resistances: failure % = 20 + Current Resistance (only for resists that actually change)
These only factor in if they are changing as a result of the enhance.
- Durability: failure % = 20 + ( Current Max. Durability / 40 )
- Lower Requirements: failure % = 20 + ( Current Lower Requirements% / 4 )
- Luck: failure % = 30 + ( Current Luck / 2 )
Drop all decimals from the calculations. Each roll is done separately.
To find the chance of success
Take each failure chance, and subtract it (after dropping decimals) from 100%. This will get you a bunch of numbers 80% and less.
Multiply all these together, and remember to adjust the decimal accordingly.
ex. 80% * 80% = 64% (i.e., .8 * .8 = .64)
A normal, non-exceptional, piece of leather armor has 2/4/3/3/3 base resists.
So, Spined leather has a 78% * 60% chance of success = 46.8%, as only 1 resist is altered, plus luck
Both Horned and Barbed have the same chance of success, as they alter all 5 resists
78%*76%*77%*77%*77%, or a tiny fraction under 77%^5 chance of success. OR, a tiny bit over 26% chance of overall success.