In 1883, after a laborious series of trials, Schweinfurt, Germany-based metalworker and turner, Friedrich Fischer, succeeded for the first time in using his own invention – the ball grinding mill – to manufacture large volumes of hardened, equally-sized, round steel balls. On 17 July 1890, Fischer received his patent (number 55783) for his ball grinding machine from the Imperial Patent Office.
By fitting hardened steel balls into the bearings of bicycles that Fischer produced himself in Schweinfurt, he ensured that they ran smoothly. At that time, the steel balls were manufactured using English manual turning machines, but the balls were susceptible to breakage and costly to produce. From 1883, the first ball grinding mill developed by Fischer enabled the manufacture of precision steel balls to accuracies of 0.020 millimetres (20 µm).
Fischer’s ingenious mill incorporates a grinding wheel that rotates eccentrically from the horizontal machining plane. Each ball rotates approximately 30 times around its almost horizontal axis, while it rotates once around its vertical axis. As a result, the ball’s entire surface area is covered by the tool and everything that protrudes is machined off until the ball has reached an almost perfectly spherical shaped ball at the end of the machining process. Further improvements by Wilhelm Höpflinger made the production of balls even more cost effective and efficient.
Fischer’s trademark, “FAG”, which stands for “Fischer’s Automatische Gusstahlkugelfabrik” (roughly translated as ‘Fischer’s Automatic Cast Steel Ball Maker’), now a Schaeffler brand, is still known worldwide. The principle of Fischer’s and Höpflinger’s invention, the centreless grinding of balls, is still used today by all ball manufacturers.
