Design and Characteristics of Ball and Roller Bearings

SINGLE ROW DEEP GROOVE RADIAL BALL BEARINGS  are the most widely used bearings and utilize an uninterrupted raceway, which makes these bearings suitable for radial loads, or a combination of radial and thrust loads.  This design permits precision tolerances even sat high speed operation.

The cage in this bearing is pressed steel.  For high speed bearings, machined brass cages are available.  Bearings with locating snap rings are also available.

PRELUBRICATED BEARINGS have integral seal, or shields, which are packed with long-life grease.  In many applications, these bearings may be used without supplementary seals, closures, or protective devices.  This design offers the lowest possible manufacturing cost to the consumer.

The boundary dimension of this type is the same as the corresponding bearings without the seals or shields.

SHIELDED BALL BEARINGS incorporate securely fastened, steel reinforced, rubber seals, fastened to a groove on the outer ring.  Contact with the inner ring is by sealing lip (Contact suffix LLU). Or, non-contact with the inner ring is by labyrinth seal (non-contact suffix LLB) to provide positive sealing at all times.

SINGLE ROW ANGULAR CONTACT BALL BEARINGS  feature raceways with high and low shoulders.  These opposing raceways are designed to carry thrust load in one direction.

These bearings may be preloaded at the factory so that the correct preload will develop within the bearing.

The bearings in this series are assembled with a specific internal clearance so that they will have a specified contact angle under stress load.  The standard contact load used by NTN is 30⁰; bearings made to 40⁰contact angle carry the suffix B.

For high speed grinding spindles the 7000C, 7200C and the 7300C series are available.  They are high accuracy bearings with a 15⁰ contact angle, and phenolic resin cages for high speed operations.

DOUBLE ROW ANGULAR CONTACT BALL BEARINGS have an inner and outer ring with a double raceway.  The two rows are so related that the contact angle is similar to a pair of back-to-back single row bearings.  The 5200 and 5300 series offer continuous races, and can carry thrust loads in either direction.  Since the 3200 and 3300 series have filling slots, it is necessary to mount them with the thrust load acting against the un-notched face of the rings.

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Some Fun Facts about Bearings

While it’s true that bearings might not come up in everyday conversations, they may never be the theme at Bingo night, or even come up during a heated game of trivia – but there are definitely a few things about bearings you don’t yet know, and they are far from boring!

Bearings Aren’t New Nowadays

Yes, there are many new ways we’ve found to implement the handy little buggers, but that’s not to say bearings haven’t in fact been around a very long time.

It’s easy to think that bearings just sprouted up out of nowhere as modern technology has risen in the last 50 years, but they’ve been around far longer than that.

Thousands of years ago, the ancient Egyptians used a form of roller bearings to build massive structures such as the great pyramids.

Remains of Roman ships dating back to 40 BC have been found with wooden ball bearings that supported rotating tables.

Bearings are Uses Everywhere

Did you ever hear the phrase, “a spider has eight legs and there’s always one within eight feet of you?” It would be easy to guess the same is true for bearings.

If you take a quick look around, you will notice bearings are everywhere, all around you. They’re in water heaters, microwaves, computers, airplanes, satellites, telescopes, washing machines, skateboards, and the list goes on and on.

Bearings are Perfect spherical object

In shape and structure, that is.

If you were to take it upon yourself to attempt to file down a ball bearing – in the how many licks does it take to get to the center of a lollipop kind of way – your file would be guaranteed to wear out long before the ball bearing ever does!

Secondly, they’re perfectly round. For a fun comparison – if you were to expand a ball bearing to match the size of the Earth, you would notice that the ball bearing would be more round than the Earth itself. This has to do with centrifugal forces pulling at the Earth, making it an oblate spheroid rather than a perfect spherical object.

Bearings Won the World’s First Bicycle Race

According to the New World Encyclopedia’s history of bearings: In August of 1869, the first French patent for ball bearings was received by Parisian bicycle mechanic Jules Suriray. Shortly after that, James Moore came in first place in the world’s first bicycle race, the Paris-Rouen, in November of 1869. His first place medal was no doubt thanks to the new bearings that had been fitted to his bike.

We Once Declared War on Bearings

During the Second World War, factories in Germany that manufactured ball bearings were often targeted to be destroyed. Reason being, the bearings were an essential part of the war industry in Germany, and thus destroying them gave the Allies a much needed headway. Schweinfurt was one location of a major bearings manufacturing plant that was targeted.

Bearings Make the World Go ‘Round'

Global demand is pushing bearing manufacturers to churn out more product, faster, with ever more innovative designs. As consumers and corporations demand more from technology, and the bearings market continues to grow, we’re sure to see bearings play an important role in our future.

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How to Calculate Friction in a Sleeve Bearing

The friction present in a sleeve bearing depends upon several factors. For example, the constant value of the coefficient of friction depends upon what materials comprise the sleeve and bearing. Other important factors include the size of the shafts, the rotational speed and the lubricant viscosity. In a rolling-element bearing, its static friction (and the torque needed to overcome that force) usually exceeds its running friction. Consider all these factors to calculate friction in a given sleeve bearing.

Determine the materials of which the inner bearing and outer sleeve are composed. Refer to tables of standard coefficients of friction to determine a rough value for the coefficient of friction between those two materials in particular. Note this dimensionless constant using the greek letter "mu" (µ).

Determine the sizes of the bearing and of the sleeve. Note the radius of the shaft using the letter "R."

Subtract the area of the bearing shaft from the area of the sleeve to calculate the radial clearance between them. Note this clearance, using the same units as for R, but use the letter "c."

Determine the viscosity of the lubricant in the bearing. Note the force per area multiplied by time with the letter "P."

Determine the speed at which the bearing revolves in the shaft. Note the revolutions per second with the letter "n."

Multiply 2 by pi squared (π^2) by µ (the coefficient of friction) by n (the speed of revolution) by R (the radius of the shaft).

Multiply P (the viscosity of the lubricant) by c (the radial clearance between shaft and sleeve).

Finally, divide the value calculated in Step 6 by the value calculated in Step 7 to complete Petroff's equation. The result is the force of the friction present in the sleeve bearing.

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