This article takes a look at alternative-material, non-metal bearings, and it turns out the first bearings of that type - wood, in this case, were the norm - not an alternative.

Bearings make the world go
’round. Much like gears, bearings
are used in practically anything
you can think of—from
toys to titanic machinery and beyond.
Another similarity to gears: they’ve been
around since the beginning of recorded
history, as Timken Process Industries’ Steve Johnson, director–process technology,
explains. (Ed.’s note: Statements from
Timken in this article pertain to rolling element
bearings only—ball, cylindrical roller,
spherical roller and tapered roller. Other
friction management systems such as fluid
film bearings, magnetic bearings etc., were
not considered.)

“I believe the first non-metal bearings
were wood. The ancient Egyptians/
Greeks, etc., used wooden logs as simple
roller bearings to move large objects.
During the industrial revolution, early
rolling element bearings were also wooden.
In modern times, certainly low-cost
plastic bearings have been used in toys,
household appliances, etc., for many
years.”

So there you go—this article is a look
at alternative-material, non-metal bearings,
and it turns out the first bearings of
that type—wood, in this case, were the
norm—not an alternative.

But there are indeed alternatives
out there today. We now have bearings
made from—or coated with—ceramics,
reinforced and non-reinforced polymers,
carbons and graphite, for example, with
other, next-generation engineered materials
almost sure to follow. And given the
ever-fluctuating cost, quality and availability
of steel worldwide, it is no wonder
that non-metallic bearings have made
tremendous gains in many markets and
applications.
“Full non-metal (ceramic) bearings
are used in some space flight and semiconductor
applications,” says Johnson.
“Metal bearings with non-metal components
such as polymer cages or ceramic
rollers are used extensively in markets
such as rail, light-vehicle systems and
machine tools. The use of hybrid ceramic
bearings in high-speed machine tool
spindles as the standard has occurred over
the last 15 years or so.”
Tom Miller, Igus Inc. bearings unit
manager/North America, adds this:

“Plastic bearings can be used in many
different industries and applications. Just
some of the industries in which plastic
bearings are being used include automotive,
medical, food and drug, farming,
solar, bikes, packaging, textile, offshore,
marine, aerospace and office furniture.

“Over the past few decades, the applications
for self-lubricating plastic bearings
have become almost endless. Some
design engineers do not believe plastic—a
material that most people equate with a
disposable commodity like a plastic fork
or spoon—will deliver superior performance.
If you are using high-performance
plastic bearings, they can be used in
almost any application—from packaging
machines and medical equipment to
environments with chemicals, extreme
loads or high temperatures.”

Looking at things from a leading
material supplier’s perspective, Victrex
technical manager Patrick Clemensen
adds, “The largest markets for non-metal
bearings are automotive transmissions,
followed by industrial pumps, compressors
and material handling applications.”

Speaking of automotive, one can safely
assume that industry has been among
the greatest consumers of bearings—of
all kinds.
“The auto industry has driven the
use of non-metal bearings in some of
the largest volume applications,” says
Clemensen. “Victrex’s PEEK material
advantages in automotive applications
include high resistance against aging and
creeping at high operating temperatures
and high circumferential speeds.”

At Igus, Miller adds that “The automotive
industry has certainly contributed
to the increased use of self-lubricating
plastic bearings, as they are an ideal choice
for this sector. They are lightweight, dryrunning,
dirt and dust-resistant, maintenance-free
and corrosion-resistant.
Plastic bearings also deliver extremely
quiet operation and eliminate vibration,
which is a key concern for many operators.
In many instances, plastic bearings
are replacing metal roller bearings in
axle journals and can be used in place of
metal bearings in shock absorbers thanks
to their low static and dynamic friction
properties.