straight and true

Masters of many arts, the craftsmen of early firearms advanced the standard of precision manufacturing.

But a present-day technician might find more mundane aspects of the siege interesting—specifically, that famous gun. We might wonder: In the 15th century, how did manufacturers drill a hole an inch or so in diameter and a few feet long, straight enough to launch a projectile, and how did they keep that hole parallel to the axis of an iron rod? The answer is that they didn't. There was more to it than simply drilling.

Their technology, primitive as it was, was the beginning of a discipline that flourished and is still being refined today. In the 15th century, it started with blacksmithing. Barrel making has gone on to evolve the complex machine tools that are now used in such familiar products as heat exchangers and gasoline engines.