Hardened copper bolts were the ¿new technology¿ that saved the Royal Navy when iron bolts no longer held ships together safely after their wooden hulls had been sheathed in copper in the mid-18th century. It is important both for naval history and for the history of the metal industry during the Industrial Revolution to understand how copper was provided for the Navy. The competing manufacturing processes have been shown to result in different patterns of preferred orientations of the tiny copper crystals that make up a solid bolt. Bolts recovered from shipwrecks of the time are up to 1m long and neutron diffraction is the only non-destructive technique that can reveal these distinctive patterns and how they vary in different parts of the bolt. Five such bolts will be examined to show their manufacturing routes. The better methods of doing this can then be applied to modern materials too