Editor's note: An updated version of this information can be found here. Bearings are used to help reduce friction. Metal-upon-metal contact produces large amounts of friction. The friction adds to ...

That is, thrust bearings where both end ‘washers’ are groved to form a ball-race, and: one washer is sized to clear the 8mm shaft and fit the 16mm bore, while the other is sized to fit the 8mm shaft ...