Re: 0.1mm
Genuine question - who is right? 0.1mm is 4/1000 of an inch. How many parts on an old Land Rover are really toleranced better than that? You mentioned the pistons, but after a few decades of wear, are they still toleranced to better than 4/1000?
Most engineering from the Fifties had quite loose tolerances as that was the best that the machine-tools of the day could do. Land Rovers certainly date from this time, so the number of parts that really need tolerances better than 1/1000 (the "few microns" mentioned by another commentator) might be rather small.
Biting the hand that feeds IT
