A real engineer finds out how much, (and by who) he/she/it's getting paid to figger out what the answer is..... how accurate the customer is gonna what the answer, how accurate the customer actually NEEDS the answer, how close purchasing can buy the answer from somebody's catalog, how accurate the shop is gonna measure the answer, and how (almost) accurate the shop is gonna cut the answer, weld it, grind it, and then paint it.
Then he's gonna tell you the same answer: "3 and a half inches".
And that is the right answer, because it is delivered in two seconds, and it is pretty darn close."