Page 11 - Craft Bearing Catalog

Bearing Types Selecting the Correct Bearing
Bearing Company Inc.

C 1

CRAFT BEARING makes a standard duty (S1 series), heavy duty (S2 series), and an extra
heavy duty (S3 series) bearings. Bearings from 1 /2 to 12 inch (or equivalent metric size) are
standard stocking items. Larger bearings are often in stock, but special orders can quickly be
provided for bearings up to 32 inches.

n Shaft Size and Tolerance

Craft split bearings are designed and In an engineered piece of equipment such as
manufactured to a close tolerance. Over time, a roller bearing, shaft tolerance and condition
actual shaft diameter in the field can vary by are of highest importance. A bearing is no better
as much as a few thousandths of an inch in than the shaft it is on. Therefore, shaft condition
different bearing positions on a single shaft. directly affects bearing performance and life.
Shaft to bearing fit becomes more critical as
load and/or speed increases. Before mounting n Product Dimensions
a bearing, the journal should be checked for In ordering a bearing for a particular
diameter, roundness, taper, and conformity to application, it may be necessary to know the
a straight edge. Roundness and taper should be bearing dimensions (height, width, length).
held within 0.001” along the length and diameter Additionally, the expected load and RPM of the
of the bearing seat. The faster an application, the application determines the bearing series need
tighter the shaft tolerance should be. (S1, S2, or S3). The Bearing Dimension section,
starting on page 26, provides dynamic, static,
’ dn value (in.) Tolerance and axial load ratings and maximum speed for
each bearing size and series.
0 – 2,000 dn + 0.000” / - 0.004”
2,000 – 4,000 dn + 0.000” / - 0.003” n Bearing Life
4,000 – 6,000 dn + 0.000” / - 0.002” All calculations to determine the load
6,000 – 8,000 dn + 0.000” / - 0.001” carrying capacities of the Craft split bearing are
based on and in accordance with ABMA and
8,000 and over dn + 0.000” / - 0.0005”
International Organization for Standardization
(ISO) standards. Bearing life is a fatigue
Where dn = shaft diameter (in.) × RPM, Craft’s calculation that estimates the ability of a bearing
tolerances for shaft fit are within the generally
accepted ABMA/ISO norms of all rolling to carry a load, commonly known as L10. The
element bearings, with due respect given for L10 is the basic life rating of a bearing, generally
speed capability and uniqueness of design. Craft given in hours or millions of revolutions, and is
bearing’s speed capability is closely comparable the minimum expected life for 90% of a group
to that of ball bearings in a like shaft size.
of like bearings. Median life is where 50% of the
group will complete or exceed the life rating, and
is approximately five times the life rating.

Bearing life
Bearing life
CR = Basic dynamic load rating
= Basic life rating in hours.

Basic life rating in hours.

Basic life rating in hours.

PR = Dynamic equivalent radial load

p = Exponent of life equation = 10/3

= Basic life rating in millions
Basic life rating in millions of revolutions.

Basic life rating in millions of revolutions.

n = Shaft revolutions per minute
of revolutions.

Frequency Equations
Frequency Equations
Ball Spin Frequency (Roller)
Ball Spin Frequency (Roller)
Craft Bearing Company, Inc. n Newport News, Virginia n www.craftbearing.com Craft Bearing Company, Inc. n Newport News, Virginia n www.craftbearing.com 9

Craft Bearing 2017 Catalog + Spe9 9 8/14/17 1:51:21 PM

Fundamental Train Frequency (Cage)
Fundamental Train Frequency (Cage)

Ball Pass Frequency Inner (Inner Race)
Ball Pass Frequency Inner (Inner Race)

Ball Pass Frequency Outer (Outer Race)
Ball Pass Frequency Outer (Outer Race)

Load Chart Equations
Load Chart Equations

Radial Load:
Radial Load:

, whichever is less
Axial Load:
Axial Load: , whichever is less