My father, a machinist in a small engineering company in southern England, told me msny tales of rebuilding worn-out, shot-up or crash-damaged Rolls-Royce Merlins during the war, and the care and effort that had to be put into the work to get anywhere near RR standards - putting a final finish on reground crankshaft journals with the finest available emery cloth etc. etc. Shift-work, of course - six to two, two to ten, and the hated ten to six (trying to sleep during the day in a house full of evacuee children!). In those days, nothing went to waste if you could re-use it!