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NTN
BEARING CORPORATION OF AMERICA |
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Introduction
to Ball Bearings
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The Basic Bearing Numbering System
Usually, with all the bearings discussed so far, the last two digits of the base bearing number indicate the diameter (size) of the bearing’s bore in millimeters. The first four (4) must be memorized.
When the last two digits of the base bearing number are 04 or larger, simply multiply the double digit number by five (5) and you have the bore size in millimeters, i.e., 04 = 20mm, 10 = 50mm, and 24 = 120mm. The third digit of the base bearing number from the right usually denotes the series (cross section size or duty) of the bearing. For any given bore size, the larger the series number is, the larger the bearing O.D. and width will be. For example, let’s consider 50mm bore SRDG ball bearings.
You are now ready to study and understand the basics of NTN's ball bearing numbering system.
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