be a steel ball for ball bearings smooth glowing and hard a symbol of perfect form but also a symbol of the precision of all ball roller and needle roller bearings deviations from the theoretical ideal geometric shape may be as minimal as one hundred thousandth of a millimeter the raceways of the rings where the balls rollers and needles will ultimately have to run have also got to be more precise than the human mind can even imagine this means elaborate painstaking care is taken with the raw materials so that their chemical composition carbide size and distribution austenitic grain size cleanliness and harden ability