Bearing Designation System - How to identify a Bearing

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0:00 Bearing Designation System
1:39 basic designation
2:06 bearing type table
2:20 width and height series
2:58 diameter series
3:23 bore diameter
4:57 suffix

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Bearings are mechanical components used to support and facilitate the rotational movement between two parts of a machine or device. They are designed to reduce friction and wear during movement, allowing a smooth and fluid rotation.

For this reason, it is crucial to carry out periodic supervision of their condition, using a qualified technician.
In the event that components need to be replaced, it is essential to identify them precisely to ensure that they are perfectly suited to the particular needs of the machine. Since there are many variants, each with its own peculiarities, careful selection is crucial.

In this situation, the JAES maintenance technician is dealing with the need to repair an electric motor which, due to many hours of work, has suffered bearing wear. (Which are now in a condition of high friction, and a reduction in the overall efficiency of the motor).

After dismantling the worn bearing, what stands out here is the presence of shields on both sides which prevent the rolling elements inside from being seen. (These shields are an optional component, designed to protect the bearing from dust and other contaminants). However, this feature makes it difficult to identify the exact type of bearing, (just by looking at its shape).

Therefore, in order to determine the bearing, it is necessary to refer to the initials usually found on the side of the rings. These initials are commonly stamped on the metal and are a designation system, consisting of a series of numbers and letters, which provide crucial information on the type of bearing and other technical specifications useful for its identification.

Each bearing manufacturer uses its own codes to identify its products. However, there is one part of the code that is part of a system used worldwide, called the " basic designation".
It reveals through a series of digits, the simplest and most important data of the bearing, which are its type and dimensions.

In this bearing we can read 6011-2Z

The initial number, "6", indicates the single row deep groove ball bearing, the most common type. Here in this legend, all the numbers and letters you might encounter are detailed, allowing you to recognise the different types of bearings.

The following figures identify the overall standardized boundary dimensions according to ISO general plans.
The second digit, in this case subscript "1", indicates the width in radial bearings (which are, as seen in the drawing, dimensions B, C, or T) or the height in axial bearings (dimension H).
The width series for radial bearings are the numbers 8, 0, 1, 2, 3, 4, 5, and 6 in ascending dimension order; while the height series for axial bearings are the numbers 7, 9, 1 and 2, again in ascending order.

The third digit identifies the bearing diameter (dimension D).
The diameter series and are numbered 7, 8, 9, 0, 1, 2, 3, and 4 (in ascending order of outside diameter)

As can be seen, these boundary dimensions are numbers that do not correspond to actual quantities, but are standardised dimensions based on the diameter of the inner bearing bore, the only measure expressed.
As a matter of fact, the last numbers symbolise the diameter of the bearing bore, i.e. the inner diameter of the inner ring. This information is fundamental as it is the dimension that must be adapted to the shaft to which it will be connected.

Bores with dimensions between 20 mm and 480 mm are identified with a two-digit number. To obtain the actual bore size, it is necessary to multiply this number by five.
In fact, on this bearing, the code 6011-2Z identifies a hole diameter of 55 mm with the number 11. (As we can also see by measuring it with a caliper).
The 10, 12, 15 and 17 mm bores are an exception. Because they are referred to by the codes 00, 01, 02 and 03 respectively.
While, generally, the diameter is explicitly indicated in millimetres and can be separated by a slash, in situations where
the holes are small, (equal to or less than 9 mm),
for those of large dimensions, (equal to or over 500 mm),
and when the size is not divisible by 5.