How Precision Balls Are Made — Technical Data Sheet 11

Balls are manufactured by a progressive series of highly automated operations. Ball blanks are cold or hot headed from rolls of wire or bar stock depending on their size and the material. The heading machine cuts off a short cylinder of the material and a moving die with a concave spherical cup drives this cylinder into a matching cup in a fixed die. The result is a spherical shape which is the ball blank.

Intermediate Steps in the Ball Making Process
Intermediate Forms in the Ball Making Process

Next, a deflashing operation removes the slight belt and small protrusions left on the surface faces by rolling them between the two hard alloy plates under high pressure. The balls are hardened, if required, by heating them to a high temperature (over 1500 degrees Fahrenheit) in an atmospherically controlled furnace, and then quenching them in a liquid bath. They are then tempered to reduce their brittleness by heating them to a low temperature (around 325 degrees Fahrenheit). Samples are checked for hardness. The grain size and metallurgical structure is inspected under a high power microscope.

The hardened balls are precision ground by rolling them between the faces of a fixed iron plate and a very hard fine-grit grinding wheel. A sample of the ground blanks are checked for burns or rehardening by etching them with NITOL solution. The next step is the lapping operation. The hardened ground balls are rolled between two cast iron plates. A slurry of very fine lapping compound is pumped over the plates. One plate is fixed while the other is rotated at a very low speed. The real secret of the extreme quality of precision balls happens here. We call it the average of errors. A large number of balls are always between the lapping plates but only the high points touch, and these errors are gradually worn down. Soon all of the balls are round and the same size. At this stage the sphericity and size have been established and are carefully inspected to A.F.M.B.A. or military standards.

The final production operation is polishing which imparts the jewel-like luster to the finished ball. The quality of this polished surface is measured by a light beam in a special interference microscope. There are very few ball plants world wide. Because it is such a unique process, few people really understand how balls are made. This is a brief generalization of the ball making process. Many of the smaller steps and tests have been omitted in the interest of brevity.

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