Heard the same story from an expert on Canadian Model A's (he has since passed). I also don't know how much of the story is true, but I will relay what I heard. Apparently, Henry took a trip across the Detroit river to visit the Ford assembly plant in Windsor, Canada. The production guys were very enthusiastic about the Robertson screws in that they were much faster to install and did not strip out as often given that they used a square driver. Henry was intrigued and made an appointment to see Mr. Robertson who had the patent on the screws. Henry made a ridiculously low offer for exclusive rights and Robertson refused. Apparently Mr. Robertson was too much like Henry in personality (i.e. hard head) and was offended that he was being treated so poorly. When he refused to grant rights, Henry offered to buy the company and Mr. Robertson told him basically to take a trip back across the river to the U.S. This incensed Henry, so he decreed that Fords made in the U.S. would never use Robertson screws. (Since Ford of Canada was a separate company, they could continue to use them without having to follow the order).