My experience with NGK plugs is that if you follow the directions (eg. you go 1/2 to 2/3 of a turn after seating as the case may be) it will end up being very close to the factory specified torque.
I have noticed that if, for example, 1/2 turn after seating is specified, my torque wrench (set to 1/2 way between the upper and lower torque specified) consistently clicks at around 9/16 of a full turn...or just ever so slightly beyond the maximum rotation specified by the spark plug manufacturer. I find this to be pretty impressive.
I have concluded these crush washers are pretty good at getting you in the right ball-park without having to use a torque wrench (but I always do anyways).
I have noticed that if, for example, 1/2 turn after seating is specified, my torque wrench (set to 1/2 way between the upper and lower torque specified) consistently clicks at around 9/16 of a full turn...or just ever so slightly beyond the maximum rotation specified by the spark plug manufacturer. I find this to be pretty impressive.
I have concluded these crush washers are pretty good at getting you in the right ball-park without having to use a torque wrench (but I always do anyways).