Answer / m asim

A typical bearing is the 6203ZZ bearing. This part number
can be divided into it's components:

6203ZZ

which means:

Type Code
Series
Bore
Suffix
The type code indicates the type of bearing. While each
manufacturer uses their own numbers, there are a few
numbers that could be considered standard in the industry.

1 Self-Aligning Ball Bearing

This kind of ball bearing has a spherical outer race,
allowing the axis of the bearing to "wander around". This
is important because misalignment is one of the big causes
of bearing failure.

2 Spherical Roller Bearing
3 Double-Row Angular Contact Ball Bearing

Designed to take axial as well as radial loads.

4 Double-Row Ball Bearing

Designed for heavy radial loads.

5 Thrust Ball Bearing

Intended for exclusively axial loads.

6 Single-Row Deep Groove Ball Bearing

Typical ball bearing. Handles light axial loads as well as
radial loads.

7 Single-Row Angular Contact Bearing

For axial (one direction only!) as well as radial loads.

8 Felt Seal

To assure that the entire inside edge of the seal touches
the inner ring, the inner ring is enlarged. If a bearing of
more normal proportions is required, the outer ring is also
enlarged, and the bearing is referred to as a "wide cup"
bearing.

32 Tapered Roller Bearing

This is the kind of wheel bearings used in cars. The
rollers are not cylindrical, but conical. They handle large
raidal and axial loads.

R Inch (Non-Metric) Bearing
Varies
N Cylindrical Roller Bearing

Instead of balls, cylindrical rollers are used. These
bearings can handle much more radial load, but can handle
much less axial load, than ball bearings.

NN Double-Row Roller Bearing

Handles greater radial loads than standard cylindrical
roller bearings.

NA Needle Roller Bearing

Needle bearings are basically roller bearings, but the
rollers are much smaller, making the bearing more compact.
Varies


Type 6, "single-row deep groove", is perhaps the most
common type of bearing.

If the bearing is an inch bearing (the first digit in the
number is an R), then the size is the digit or digits
immediately following the R, in 16ths of an inch. An R8-2RS
bearing, for example, has an 8/16th or 1/2 inch bore.

If the first digit is a number, however, it is a metric
bearing, and the second digit is the series, which reflects
the robustness of the bearing. The series are, from
lightest to heaviest: 8 Extra thin section
9 Very thin section
0 Extra light
1 Extra light thrust
2 Light
3 Medium
4 Heavy


Yes, they go in that order. Gotta keep things simple, you
know.

Each of these series also establishes a relationship
between the bore size, outer diameter, and thickness of the
bearing, in accordance with ISO standards. I have no idea
what they are.

The third and fourth digits indicate the bore size in
millimeters. Except for 0 through 3, the bore size is
simply five times the third and fourth digits together. 0
through 3, however, are different: 00 10mm
01 12mm
02 15mm
03 17mm


If there is no fourth digit - for example, a 608 bearing, a
common roller skate bearing - then the size is the last
digit in millimeters.

The last letters indicate something special about the
bearing. For example: Z Single shielded
ZZ Double shielded
RS Single sealed
2RS Double sealed
V Single non-contact seal
VV Double non-contact seal
DDU Double contact seals
NR Snap ring and groove
M Brass cage


And then there are the completely off-the-wall bearing
numbers, like 499502H. I have no idea what that number is
supposed to mean, but it applies to what is basically an
R10-2RS bearing, only a bit thicker and with a groove and
snap ring.

Examples
Common Skate Bearings
Number Bore
(mm) O.D.
(mm) Width
(mm)
608 8 22 7
627 7 22 7
688 8 16 4
698 8 19 6

All these bearing numbers start with 6, which tells us
they're Single-row deep groove ball bearings. The second
digits tell us the robustness of the bearings. The last
two, in series 8 and 9, are very thin and lightweight
bearings, while the first, in series 0, is an "extra light"
bearing without being abnormally thin. The third bearing,
in series 2, is the most robust of all, being
merely "light".

Light vs Heavy Comparison

Consider the following three bearings: Number Bore
mm O.D.
mm Thickness
mm
6010-2RS 50 80 16
6210-2RS 50 90 20
6310-2RS 50 110 27


We can see from the part numbers that they're all 50mm
single-row deep groove ball bearings. However, we can also
see that they're each a different series; specifically,
Extra Light, Light, and Medium. Compare the O.D. and
thickness of each bearing, and you can see how the Extra
Light bearing (series 0) is the smallest, and the Medium
Bearing (series 3) is the largest. The larger bearing can
take much more load than the smaller bearing, though how
much depends on the manufacturer and the RPM the bearing is
run at.

Number Bore
mm O.D.
mm Thickness
mm
6904-2RS 20 37 9
6004-2RS 20 42 12
6204-2RS 20 47 14
6304-2RS 20 52 15


These are all 20mm single-row deep groove ball bearings of
different series. The first, of series 9, is a "very thin
section" bearing, meaning it is much thinner than usual -
it is only 25% as thick as its O.D., while the others are
approximately 30% as thick as their O.D.

Answer / carl gomes

A bearing is essentially 'a part of a machine that bears friction'. It is always used to reduce the friction between 2 revolving parts or between a fixed part and a moveable part.

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