A quality ball bearing is a thing of great precision. The rings and balls are machined to fine tolerances and high levels of roundness. The balls and the ball tracks (or raceways) are highly polished so the bearing will rotate very smoothly and easily. Frictional torque or in simple terms, turning resistance, is extremely low. Unlubricated bearings have the lowest turning resistance but steel ball bearings should be lubricated unless turning speeds are very low. They can be lubricated with a low torque instrument oil but, depending on speed and running time, this may mean they need to be constantly oiled with an oil bath, jet or spray. A simpler alternative is to use a shielded bearing, pre-lubricated with a finely filtered, low torque grease to provide a constant film of oil between balls and raceways while also helping to radiate any heat away from the points of contact. Imagine the heat, vibration, turning resistance and rapid wear that would result from rotating a steel shaft, at speed, in a steel housing without the use of bearings. The noise and the excessive amount of steel debris would soon let you know that something was wrong. We have come a long way from the days of packing grease or fat between wooden cart wheels and axles to reduce friction and with constant advances in manufacturing and steel and lubricant technology, the number of low friction options for a wide variety of products continues to grow.