From: Robert Bastow <teenut@home.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Ball Bearings - how are they made
Date: Tue, 28 Sep 1999 15:38:32 GMT

Mark Fullerton wrote:

> Just one of those curious questions that has been bothering me.
>
> How are SS ball bearings manufactured?
>
> They are so perfectly round and so cheap.
>
> I was trying to visualize how it would be done and couldn't come up with a way
> to do it.
>
> Just wondering . . .


Same way that regular bearing balls are made! (You did mean the balls..not the
complete bearing I presume?)

High speed, cold heading machines take a wire or rod feed, chop it to length and
cold forge a ball to fairly close limits of size and sphericity.  Basically this
is done by taking a cut slug of the right volume and "bonking" it between two
hemispherical dies.

Heat treatment follows..in continuous conveyor fed furnaces.

Then the balls are fed in a continuous stream to a series of grinding and
lapping machines.  These look like the old flour grinding mills..two discs
contra-rotating (or rotating at differential speeds) the balls feed in the
center and sphericity is 'Generated" just as you would form a ball of play-do by
rolling it between your hands.

Gauging is automatic..usually by rolling the balls along two, slightly divergent
hardened knife edges..amazing accuracy!

Balls are graded for size and sent off to be assembled with similarly graded
inner and outer rings on a "Selective Assembly" basis.  This may be done in the
building next door..or one half way around the world!!  Bearings are a
Multinational concern!

The assembly plants run, 24/7/365 fully automated, on an almost "lights out"
basis.  Noisy places they are..Busy but no one about unless something needs
fixing.

A modern ball bearing can go through every stage of manufacture, assembly,
packaging, shipping and assembly (For instance into an automobile) without being
touched by human hand or seen by human eye.

Inexpensive..Yes!

Cheap??   These plants cost BILLIONS..but people Like SKF can ship a complete
plant, in "knocked down" condition, to a green field site any place in the world
and have it up and producing in a month from get-go.

teenut

From: Bob Chilcoat <viewREMOVEptmd@erols.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Ball Bearings - how are they made
Date: Tue, 28 Sep 1999 13:07:54 -0400

My father described a ball bearing final inspection machine he once saw
in Switzerland.  It consisted of a gravity-fed inlet ramp where a stream
of balls would be launched toward a series of small steel anvils at a
precise speed.  The anvils were angled at precise orientations, so that
the balls, if perfect, would bounce from one anvil to another until
eventually they would bounce through a hole ("passed") and on for
packaging or assembling into races.  Any imperfect ball would eventually
miss an anvil and would would fall to the bottom of the machine through
another hole ("failed").  This thing was fed by the production line as
fast the the balls were made, and the two output streams ("passed" and
"failed") went the rest of the process, or the reject bin, as
appropriate.  Simple but fast, effective, and zero operator
intervention.

Bob

G: "If we do happen to step on a mine, sir, what do we do?"  EB: "Normal
procedure, lieutenant, is to jump 200 feet in the air and scatter
oneself over a wide area."
-- Somewhere in No Man's Land, BA4

From: Robert Bastow <teenut@home.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Ball Bearings - how are they made
Date: Tue, 28 Sep 1999 20:02:51 GMT

DanD wrote:

> Great description of the balls - now, for thoes of us out here, what
> about getting those balls in between the two races? Dan


That's the easy bit!

Again, it is a fully automated assembly,  Rows and rows of machines each with
large hoppers full of balls...In all my years of automated orientation, feeding
and assembly of thousands of different parts, I have never found one that is as
difficult to bulk feed as steel balls.

Sounds silly, but until they are all in a row, in a track or tube the little
buggers will jam up at the slightest provocation.  The recent thread on lead
shot and different packing matrices made me smile..and cringe.

If you don't believe me, get a large funnel, fill it half full of balls and see
how fast you can shake them out of the end.  Truth is..you can't!  Regardless of
the size of hole in the bottom!  They will flow until they form a bee hive
shaped cavity..actually an eliptical cross section..and there they will
stay..locked and no amout of shaking or poking will shift them!!

Any hoo!  Moving right along..The balls are dumped into the assembly machines in
carefully graded lots..maybe five or ten different size gradations each
demanding its own machine.  Inner rings and outer rings, similarly graded are
fed in on overhead tracks...thousands of feet of track in a plant..all jingling
and jangling like a cross between the background noise in a Vegas Casino,
amplified a thousand times and fed into the Musak at Disney's "Its a Small,
Small World"  Without ear protection you would go stark, staring, bonkers in an
hour!!

As an aside..Because of their expertise in track conveyor systems, SKF are one
of the world leaders in this type of prefab. automation tracking systems!!

The inner rings and outer rings are fed into stations on a continuous motion,
vertical axis, turret type assembly machine.  The rings are held to one side
while the quota of balls is dropped in and then a "Spider" pops up from
underneath, separating and centralising the rings and balls while the two sides
of the cage are inserted and either riveted, clipped, glued or spot welded
together.

Some types have the cage injection moulded in place, some, newer types, have a
one sided plastic cage that simply clips over the balls. (Though getting them to
the right place, at the right time, right side up, was one of my nightmare
applications.  The little suckers were more "Hooky" than a fishermans hat and
clung together like a ball of spiderlings!) This all taking place at speeds up
to 120 completed bearings per minute, per machine!!  (And you wonder why I quit
the automation business!!!)  MAD I tell you, MAAAADDD!!

On some high capacity bearings (large number of balls) the inner and outer rings
have to be sprung out of round by a precise amount to get the last few balls
in.  Others have loading slots cut in the outer and sometimes the inner
rings..of precise depth that they don't interfere with the track of the balls in
service.

As I said...Thats the easy bit!

teenut

From: Robert Bastow <teenut@home.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Ball Bearings - how are they made
Date: Wed, 29 Sep 1999 20:25:54 GMT

Hoyt McKagen wrote:

> Robert Bastow wrote:
> >  Inner rings and outer rings, similarly graded are
> > fed in on overhead tracks..
>
> You forgot to tell us that IR and OR are forged in one piece and after
> machining/seperation/HT/grinding are kept matched to each other all the
> way through.


Hmmm!

Thats a new one on me Hoyt.  I don't dispute that it is done in certain
circumstances. But all the inners and outers I ever saw made, started life being
machined to size, from hollow forged bar, on multi spindle automatics.

Of course these were only bearings up to about 3" o/d and different procedures
may well be used on larger ones.

The largest bearing I ever had a hand in making, was a thrust bearing about 24
feet in diameter!!

It was a replacement slewing bearing for a HUGE dockyard crane, built by my
company a half a century earlier.

I was an "oily rag" (apprentice) at the time, in about the third year of my six
year "time"  Working on a 42 foot diameter (not a typo!!) vertical boreing mill.
(VTL to some)

The upper and lower bearing rings, of about a 2 foot square section had been
forged and heat treated in Sheffield and I got the job to machine them.  After
roughing out all over with brazed carbide tip tools, each with a 2" square
shank..(indexable carbide tips were in their infancy back then) and rough
machining the ball track to template, it was then finish ground (The ball groove
only), on the boring mill using a BIG toolpost grinder and a radius arm
attachment.

IIRC the Bearing balls were over six inches diameter, and each one came packed
in its own wooden crate!!

Great work when you can get it!!

teenut

From: Robert Bastow <teenut@home.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Ball Bearings - how are they made
Date: Wed, 29 Sep 1999 20:31:17 GMT

David R Brooks wrote:

> Robert Bastow <teenut@home.com> wrote:
>
> >Then the balls are fed in a continuous stream to a series of grinding
> >and lapping machines. These look like the old flour grinding mills..two
> >discs contra-rotating (or rotating at differential speeds) the balls
> >feed in the center and sphericity is 'Generated" just as jou would form
> >a ball of play-do by rolling it between your hands.
> ...
>  I would have thought (indeed my old school geometry book explicitly
> stated) that this was likely to produce not spheres, but
> constant-breadth polygons (strictly, polyhedra). How does the process
> avoid that?

I dunno...just describing what I saw.  It may well be that they are contained in
pockets or tracks as an earlier writer stated.

Come to think of it..there must be a three point contact..as in a centerless
grinder..otherwise there would be a natural tendency to produce a lobular,
constant diameter body.

teenut

From: Robert Bastow <teenut@home.com>
Newsgroups: rec.crafts.metalworking
Subject: Re: Ball Bearings - how are they made
Date: Thu, 30 Sep 1999 13:32:19 GMT

Hoyt McKagen wrote:

> Robert Bastow wrote:
>
> > Thats a new one on me Hoyt. I don't dispute that it is done in certain
> > circumstances. But all the inners and outers I ever saw made, started
> > life being machined to size, from hollow forged bar, on multi spindle
> > automatics.
>
> I've seen shots of the inner and outers still attached; they offset them
> across a narrow conical land but they do come out of the same die. I
> don't know what sizes or if these are special purpose but I thought that
> was the common way to do it. Obviously for large specials this would not
> be practical. The reason I've heard for it is to make sure the races are
> matched fatigue-wise.

I certainly can see where that might be called for, especially in high
performance bearings.

If the bearing races were being made from individual forgings, I would expect
that they were up at the sharp end of performance and price.

However, As the Overseas Marketing Manager for a MAJOR tubing company, I sold
tens of thousands of tons of hollow bar to bearing manufacturers world wide and
most of it had wall thickness sufficient only for inner or outer races..not
both.

teenut