I found this through http://www.google.com
(Campagnolo bearings are machined to a 1 micron tolerance!, if memory serves)
Subject: Re: How are ball bearings made?
From: email@example.com (W. Kaiser)
Chris Delikatny (firstname.lastname@example.org) wrote:
> How are ball bearings made?
I knew I had something about this buried in paper, and I found it. It's a six page pamphlet from Atlas Balls division of SKF called "How Balls are Made Round." I've gleaned the following information from the pamphlet.
They make balls from 1/32" to 2-5/8" Dia. A chrome alloy steel is used. Balls up to 1" dia. are cut from wire, and pressed between concave dies in a cold heading machine. Balls from 1" to 1-5/8" are cut hot from bar stock and pressed between concave dies. Balls over 1-5/8" dia are sheared cold from bar, then heated and pressed between dies. This leaves a sort of spherical lump of metal, with excess material around the equator,
called flash. On the larger balls this flash is removed on a double end machine
with file cut discs.
The next step is rill filing, which removes the rough surface of the ball and gets down to clean, solid metal. The machine has two cast iron discs, one rotating and one stationary, with concentric grooves. The balls follow a predetermined path through the machine. They are passed through over and over until they are within .001" of round. The machine can process up to 750 lb. of balls at one time, and processing time ranges from 8 to 20 hours. A picture shows a machine with vertical disks and a horizontal spindle.
The balls are then tumbled in barrels spinning on the end of a rotating arm. The balls are polished in the tumbler until uniform and smooth.
The balls are then heat treated in atmospherically controlled furnaces. The furnace doesn't decarburize the surface, and leaves it clean and smooth. The balls start into the furnace at room temperature, and move to progressively hotter areas. At the proper temperature they are quenched, then tempered. They should be uniformly hard from center to outside.
The balls are then precision ground. The balls roll against hard grinding wheels, following a path determined by guide plates. After 12 hours the balls are true to size and round to within .0001".
After grinding, the balls are lapped between a stationary and revolving cast iron plate. They are constantly bathed with a special lapping compound. Lapping leaves the balls within 27 millionths of an inch to size and roundness. For precision work, they are lapped more, until within 3-5 millionths of an inch. A picture shows a machine with horizontal disks and a vertical spindle.
That's the process, and this is about all I know about it. If there are any other questions, I probably can't answer them, but this should give you some idea of how balls are made. I don't have information on how the rest of the ball bearing is made, but that process is probably more straight forward than making balls.
There are three ways to do a job: good, cheap, and quick.
You can have any two.
A good, cheap job won't be quick.
A good, quick job won't be cheap.
A cheap, quick job won't be good.
[Edited by pat5319 on Dec 28th at 10:52 PM]