The allowable Trail-and-Error in a company is inversely proportional to the amount of "Error-then-Trial", if you get what I mean.
That is to say..., if failure is not an option and things are expected to work correctly right out of the gate then there may be a "trial" after any "error".
But if...
Once upon a time, back in the days of board drafting, we old folks were taught this is how to read a thread note:
1/4-20 UNC
1/4 = Major Diameter in inches
20 = Threads per inch
Everybody in agreement so far?
How about this one:
1-8 UNC
1 = Major Diameter in inches
8 = Threads per inch...