Despite mass production, screws were custom-made by machinists. No one could find the same screw on a different street, let alone in different cities.  England’s Sir Joseph Whitworth, attempted standardization first. He developed the Whitworth thread in 1841. In 1864 in America, William Sellers proposed a separate standard that simplified the Whitworth design by adopting a thread profile of 60 and a flattened tip (in contrast to Whitworth’s 55 angle and rounded tip). These two standards are still used and are known today as the British Standard Whitworth (BSW threads) and the United States Standard Threads (USS threads)