Rolls-Royce practice and American manufacturing both worked to tight tolerances. The difficulty arose when British design drawings had to be converted for American production. Terms that appeared to use the same imperial system did not always carry precisely the same definitions on both sides of the Atlantic. Technology transfer requires shared standards as well as access to plans and machine tools.
Notable Point · 50:43-51:27
When British and American measurements complicated Merlin production
American production of the Merlin exposed small but consequential differences between British and American imperial measurement conventions.