It certainly is used, but how often it is used can vary with the nature of the work. Nothing exotic mind you; just simple addition, subtraction, multiplication and division. You often need to convert fractional measurements into decimal ones and vise-versa-- Measurements, clearances, extrapolation and interpolation of data/readings/graphs to name just a few instances. I've gotten good at converting Centigrade to Fahrenheit in my head...I guess I'm too set in my ways to accept Centigrade readings at face value without a "what's the *real* temperature?" question in the back of my head. ---- BTW, got a question for you: I realize that the term "Engineer" in Britain is more or less analogous to the US' "mechanic"...but what is a "fitter" and what is the difference between they and engineers?