by John Carter

Created on: October 09, 2008

How to make precision steel balls

The ball grinding and lapping machines were invented in Schweinfurt Bavaria, Germany by Friedrich Fisher in the late 19th Century. Schweinfurt was the target of some large bombing raids in 1943 designed to disrupt the production of ball bearings during WW II. Fisher designed this machine to make high precision balls of uniform size. His invention ushered in the worldwide ball bearing industry. FAG, the company he formed is still in business and is one of the world leaders in manufacturing ball bearings.

Precision steel balls come in many sizes depending on their use. Miniature Steel Balls that this discourse is mainly about are considered those steel balls ranging from 0.010" to 0.625." Other sizes can range above 0.625" to several inches in size depending upon their use. The largest steel balls were used in battleship turrets to make the turret turn smoothly. Other super-sized balls were used in swing bridges to make the deck of the bridge rotate. In either case the balls were placed in a horizontal grooved race holding several balls in tandem. The rough balls are made as forgings usually from 52100 type hi-carbon/chrome or similar steel that is then ground and lapped to finished size. The super-sized balls were made individually by grinding and lapping the rough balls one at a time in a special grinding machine having two grinding/lapping heads set at a 60 angle from each other. The heads were each equipped with a cup shaped grinding wheel, and soft metal cup shaped lappers. It takes several hundred hours to grind and lap a ball of this size. Another way of grinding and lapping these super-sized balls was by placing them between two ring shaped plates with one plate capable of rotating, and the other plate being stationary. It is possible to exert great pressure on the balls by tightening the top plate onto the lower plate. In practice the device looks a lot like a wine press with a rotating plate on the bottom, and a movable stationary plate on top. This is basically the form that all grinding and lapping machines take.

Other then these special super-sized balls the smaller balls are made by other processes, depending on their size. Generally they are all made by variations of the same process. The different kinds of balls are segregated by size into different groups. Each size range of balls presents the manufacturer with a different set of problems that are subdivided by size range. The largest balls will often develop a

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