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Bearing Dimensions

Sizing Scheme: A system or table including the external dimensions of rolling bearings.

 

Bearing Series: A group of specific types of rolling bearings with progressively increasing dimensions, usually sharing the same contact angle and exhibiting a certain relationship between their dimensions.

 

Size Series: A combination of width or height series and diameter series; for tapered roller bearings, it also includes an angle series.

 

Diameter Series: Part of the current standard dimensional scheme in my country. An increasing series of bearing outer diameters; for each standard bearing inner diameter, there is an outer diameter series, and there is often a specific relationship between the two diameters.

 

Width Series: Part of the current standard dimensional scheme in my country. An increasing series of bearing widths; for each diameter series of bearing inner diameters, there is a width series.

 

Height Series: Part of the current standard thrust bearing dimensional scheme in my country. An increasing series of bearing heights; for each diameter series of bearing inner diameters, there is a height series.

 

Angle Series: Part of the current standard tapered roller bearing dimensional scheme in my country, a specific range of contact angles.

 

External Dimensions: A dimension defining the outer shape of the bearing. Basic external dimensions include inner diameter, outer diameter, width (or height), and chamfer dimensions.

 

Bearing Inner Diameter: The inner ring diameter of a radial bearing or the shaft ring diameter of a thrust bearing.

 

Bearing Outer Diameter: The outer ring diameter of a radial bearing or the housing ring diameter of a thrust bearing.

 

Bearing Width: The axial distance between the end faces of the two raceways defining the width of a radial bearing; for single-row tapered roller bearings, it refers to the axial distance between the back faces of the outer and inner raceways.

 

Bearing Height: The axial distance between the back faces of the two washers defining the height of a thrust bearing.

 

Ball Diameter: The distance between two parallel planes tangent to the surface of the ball.

 

Roller Diameter: The distance between two parallel tangents to the roller surface in a plane perpendicular to the roller's centerline (radial plane). When calculating rated load, the radial plane at the center of the roller is used.

 

Roller Length: The distance between two radial planes including the roller's end. However, the "roller length" used when calculating rated load is the theoretical maximum contact length between the roller and the raceway at the shortest point of contact.

 

Nominal Inner Diameter (Outer Diameter): The diameter of the cylinder enclosing the theoretical surface of a basic cylindrical inner bore (cylindrical outer surface). The diameter of the cone enclosing the theoretical surface of a tapered bore in a specified radial plane. The diameter of the spherical surface enclosing the theoretical surface of a basic spherical surface.

 

Nominal Ring Width: The distance between the two theoretical end faces of the bearing ring. Generally, it is the reference value (basic dimension) for the actual width deviation.

 

Actual Bearing Width: The distance between the intersection points of the centerline of the radial bearing and the two tangent planes defining the actual end faces of the rings that define the bearing width. The bearing width is defined by the inner and outer ring end faces.

 

Note: For single-row tapered roller bearings, this is the distance between the bearing centerline and the intersections of two planes: one tangent to the actual back surface of the inner ring, and the other tangent to the actual back surface of the outer ring. At this point, the inner and outer ring raceways, as well as the inner edge of the inner ring back flange, are in contact with all rollers.

 

Actual bearing height: The distance between the centerline of the thrust bearing and the intersections of the two tangent planes on the actual back surfaces of the washers defining the bearing height.

 

Nominal ball diameter: The diameter value generally used to identify ball dimensions.

 

Nominal roller diameter: The diameter value generally used to identify roller diameter. For symmetrical rollers, it refers to the theoretical diameter in the radial plane passing through the middle of the roller length; for asymmetrical rollers, it is the largest theoretical diameter (i.e., in the radial plane including the imaginary sharp corner of the large end of the tapered roller).

 

Rolling bearing tolerances: Under normal conditions, at a temperature of +20℃, the bearing and its parts shall not be subject to internal stress caused by external forces (including measuring load and the weight of the parts themselves), and their external dimensions shall not exceed the deviation range of the nominal dimensions.