Being I work in machine shops I have to use both. Usually when machining a part I use English measurements. But if I have to fix the machine of change the tooling I have to use metric sockets and Allen keys. But as for My robotics team, we're die hard English sytem users. the only metric parts on our bots we're a few Allen head screws. But if I'd have to choose between metric and English I'd have to say English, plus if suddenly the world switched to metric I wouldn't be able to use my vernier or micrometer

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Whats the difference between mechanical engineers and civil engineers?
Mechanical engineers build weapons, civil engineers build targets