It is said that Luck may effect the rate of forge. In order to have such a test, I make myself as a lawful thief with Justice. Such I can examinate as a 52 LUK character.
Following what presented in Japanese wiki, all forging stones give vary benefit of rate and depends on 2 factors:(1) quality of the targeted item, and (2) lvl of the stone.
there is an example, for a normal item, the base rate of +2 to +3 is 60%. A lvl 1 stone give this normal item 8% rate increasing. So the total rate will be (60+8)%=68%, and the blacksmith will tell you " A little worried".
There is aa hypothesis in my mind about if LUK adds bonus point when a dice rolls? I wonder if every 10 LUK increase 1% rate increasing but not presented in what the blacksmith's announced?
I collected 80 mage hands and hundreds of lvl 1 forge stones
for each forging, I only use 1 lvl 1 stone to minimize to cost of this investigation.
According to the simulation of this progress by Matlab
(in simulation i forge 8000000 items to cancel the noise, but in game...I need more donation)
If no other effective factor exist, for eample, LUK, the result shows as the following:(per 80 items)
0.18 to +7 ; 2 fails on +6 to +7; 8 fails on +5 to +6; 17 fails on +4 to +5; 24 fails on +3 to +4
If LUK effective factor exist and give 5% bonus, the result will show as the following:(per 80 items)
0.5 to +7 ; 3.4 fails on +6 to +7; 10.5 fails on +5 to +6; 19 fails on +4 to +5; 24 fails on +3 to +4
and as I tested in game with 52 LUK, I got
0 to +7 ; 2 fails on +6 to +7; 8 fails on +5 to +6; 15 fails on +4 to +5; 27 fails on +3 to +4
the result shows that there seems no significant difference between the result of 0 LUK simulation and the result of my test.
Looks like I've to discard this hypothesis (sigh)