[ropz]

My father is a retired South Wales steelworker - he worked in the Hot Mill, which is where you put slabs of steel in, and take huge coils of hot rolled steel out (http://en.wikipedia.org/wiki/Rolling_%28metalworking%29). The building is half a mile long, and the thickness of the steel slab is gradually reduced as it passes through dozens of rolling stations - pairs of rollers (or rolls as they're called).

To get the best product quality, it's important to monitor the shape of the rolling surface of each roll. If they distort out of tolerance, they have to be taken offline and machined to a new finish - something that would stop production for hours.

My father told me of the time when they bought an expensive new computerised lathe to reduce the time it takes to fix up the rolls - this was in the 1980s when a PC on a production line was still a thing of wonder. For a while, everything worked as planned. Then, for some reason, the quality of the reconditioned rolls dropped drastically. Despite the fact that the PC dump showed that the rolls had perfect surfaces and profiles, production defects skyrocketed and it was discovered that the reconditioned rolls were to blame.

To cut an even longer story short - they eventually discovered that the lathe operator had taught himself how to edit the PC logs (in hex!) to make the results look good, without having to get down and actually do the work.