1、 Overall dimension

1. Boundary dimension

A dimension that defines the outline of a bearing. The basic outline Common Terms dimensions are inner diameter, outer diameter, width (or height) and Chamfer dimensions.

2. Bearing bore diameter

Inner diameter of inner ring of radial bearing or inner diameter of shaft ring of thrust bearing.

3. Bearing outer diameter

Outer diameter of outer ring of radial bearing or outer diameter of race of Common Terms thrust bearing.

4. Bearing width

The axial distance between the end faces of two ferrules defining the Common Terms width of a radial bearing. For a single row tapered roller bearing, it refers to the axial distance between the back of the outer ring and the back of the inner ring.

5. Bearing height

The axial distance between the back Common Terms faces of the two washers defining the height of the thrust bearing.

6. Ring (washer) chamfer dimension

The extension of the chamfered Common Terms surface of the ferrule (washer) in the radial or axial direction.

7. Radial chamfer dimension

The distance from the imaginary sharp corner of the ferrule or washer to the intersection line between the Common Terms end face of the ferrule or washer and the chamfered surface.

8. Axial chamfer dimension

The distance from the imaginary sharp corner of the ferrule or washer to the intersection of the inner hole or Common Terms outer surface of the ferrule or washer and the chamfered surface.

9. Flange width

The distance between the two end faces of the flange.

10. Flange height

Radial dimension of flange. The height of the outer flange is the radial Common Terms distance between the outer surface of the flange and the outer surface of the outer ring.

11. Snap ring groove diameter

Diameter of cylindrical surface of stop ring groove

12. Snap ring groove width

The axial distance between the two Common Terms ends of the stop ring groove.

13. Snap ring groove depth

The radial distance between the Common Terms cylindrical surface of the stop ring groove and the outer cylindrical surface.

14. Aligning surface radius

Radius of curvature of spherical surface of self-aligning seat ring, self-aligning seat washer, self-aligning Common Terms outer ring or self-aligning outer seat ring.

15. Sligning surface centre height

The axial distance between the Common Terms curvature center of the spherical back of the self-aligning race of the thrust bearing and the back of the opposite shaft race.

2、 Dimension associated with tolerance

1. Nominal bore diameter (outside diameter)

The diameter of a cylinder enclosing the theoretical surface of a basic Common Terms cylindrical inner hole (cylindrical outer surface). The diameter of a cone enveloping the theoretical surface of a conical hole in a specified radial plane. The spherical diameter of the theoretical surface enveloping the basic spherical surface.

Note: for the nominal inner diameter and nominal outer diameter of rolling bearing, it is generally the reference value of the deviation between the actual inner hole and the outer surface.

2. Nominal ring width

Distance between two theoretical end faces of bearing ring. It is generally Common Terms the reference value (basic dimension) of the actual width deviation.

3. Nominal bearing width (bearing height)

The distance between the two theoretical end faces of the ferrule (the back of the washer) is used to limit the width of the radial bearing (the height of the thrust bearing). It is generally the reference value (basic dimension) of the actual width or actual height deviation of the bearing.

4. Actual bearing width

The distance between the intersection of the axial line of the radial bearing and the two tangent planes of the actual end face of the ferrule defining the bearing width. The bearing width is limited by the end face of the inner ring and the end face of the outer ring.

Note: for single row tapered roller bearings, it is the distance between the intersection of the bearing axis line and the following two planes: one plane is the plane tangent to the actual back of the inner ring, and the other is the plane tangent to the actual back of the outer ring.

At this time, the inner and outer race raceways and the inner edge of the back edge of the inner race are in contact with all rollers.

5. Actual bearing height

The distance between the axial line of the thrust bearing and the intersection of the tangent planes of the two actual back surfaces of the washer defining the bearing height.

6. Deviation of the actual bearing height

Difference between actual height and nominal height of thrust bearing.

7. Nominal chamfer dimension

Chamfer dimension as datum.

8. Radial single chamfer dimension

The distance from the imaginary sharp corner of the ferrule or washer to the intersection of the chamfered surface and the end face of the ferrule or washer in a single axial plane.

9. Axial single chamfer dimension

The distance from the imaginary sharp corner of the ferrule or washer to the intersection of the chamfered surface and the inner hole of the ferrule or washer or the surface of the V-belt in a single axial plane.

10. Allowable single chamfer dimension

Allowable large radial or axial single chamfer size.

11. Nominal ball diameter

It is generally used to identify the diameter value of the ball size.

12. Single diameter of a ball

The distance between two parallel planes tangent to the actual surface of the ball.

13. Mean diameter of a ball

The arithmetic mean of the large and small single diameters of the ball.

14. Ball diameter variation

The difference between the major and minor diameters of the ball.

15. Ball lot

It is assumed that a certain number of balls with the same manufacturing conditions are considered as a whole.

16. Ball grade

Specific combination of ball size, shape, surface roughness and gauge value difference.

17. Ball gauge

The small difference between the average diameter of the ball batch and the nominal diameter of the ball, which is a quantity in a determined series.

18. Ball gauge

The amount of a given series close to the true deviation of the ball gauge value of the ball batch.

19. Nominal diameter of a roller

It is generally used to identify the diameter value of roller diameter.

For symmetrical rollers, it refers to the theoretical diameter in the radial plane passing through the middle of the roller length, and for asymmetric rollers, it is a large theoretical diameter (i.e. in the radial plane including the imaginary sharp angle at the big end of tapered rollers).

20. Single diameter of a roller

The distance between two straight lines tangent to and parallel to the actual surface of the roller in a plane perpendicular to the axis of the roller (radial plane).

21. Nominal length of a roller

It is generally used to identify the length value of roller length.

22. Actual length of a roller

The distance between two radial planes including the actual end of the roller.

23. Roller gauge

Within the specified same radial plane, the diameter deviation range limited by the upper deviation and lower deviation of the average diameter of a single plane of the roller from the nominal diameter of the roller. For cylindrical rollers and needles, the plane passes through the middle of its length.

24. Roller grade

Specific combination of roller diameter and shape tolerance.

25. Deviation from circular from

The radial distance between two concentric circles of the measured contour is the roundness error.

26. Deviation from cylindrical form

The radial distance between two coaxial cylinders of the measured contour is the cylindricity error.

27. Deviation from spherical form

The large radial distance between the inscribed sphere of the contour surface (inner surface) or the circumscribed sphere surrounding the contour surface (outer surface) and any point on the contour surface in any equatorial plane.

28. Radial run out of assembled bearing inner ring

When the inner ring is at different angular positions, the difference between the large and small diameter distance between the inner hole surface and a fixed point relative to the outer ring.

The rolling elements at the angular position of the above points or at both sides near them shall be in contact with the inner surface of the inner race, outer race raceway or inner race back flange (tapered roller bearing), that is, all parts of the bearing are in the normal relative position.

When the outer ring is at different angular positions, the difference between the large and small diameter distance between the outer diameter surface and a fixed point relative to the inner ring.

At or near the angular position of the above points, the rolling elements on both sides shall be in contact with the inner and outer race raceways or the inner surface of the back edge of the inner race (tapered roller bearing), that is, all parts of the bearing are in a normal relative position.

30. Radial internal clearance

When there is no external load, the arithmetic mean of the radial distance of one ferrule moving from one radial eccentric limit position to the opposite limit position relative to the other ferrule in different angular directions.

This average value includes the mutual displacement of the ferrule or washer at different angular positions and the displacement relative to the ferrule or washer when the rolling element group has different angular positions.

31. Theoretical radial internal clearance

The outer ring raceway contact diameter minus the inner ring raceway contact diameter and then minus twice the rolling element diameter.

32. Axial internal clearance

The arithmetic mean of the axial distance of one ring or washer moving from one axial limit position to the opposite limit position relative to another ring or washer without external load.

This average value includes the mutual displacement of the ferrule or washer at different angular positions and the displacement of the rolling element group relative to the ferrule or washer at different angular positions.

3、 Axial correlation

1. Bearing axis

The theoretical rotation axis line of rolling bearing refers to the axis line of inner ring for radial bearing and the axis line of shaft ring for thrust bearing.

2. Inner ring (shaft washer) axis

The basic cylindrical hole or conical hole of the inner ring (shaft ring) is the axis line of the inner cylinder or inner cone.

3. Outer ring (housing washer) axis

If the outer surface of the outer ring is cylindrical, the axis line of the external cylinder on the outer surface is the axis line of the outer ring. If the surface is basically spherical, the line perpendicular to the reference end face of the outer ring through the center of the external sphere on the outer surface of the ferrule is the axis line of the outer ring.

4. Cone (cup) axis

The axial line of the inner ring (outer ring) of tapered roller bearing.

5. Radial plane

The plane perpendicular to the axis and parallel to the reference end face of the ferrule or the tangent plane on the back of the washer can be regarded as the radial plane.

6. Radial direction

The direction through the axis in the radial plane.

7. Axial plane

The plane containing the axis.

8. Axial direction

Direction parallel to the bearing axis. The direction perpendicular to the reference end face of the ferrule or the tangent plane on the back of the washer can be considered as axial.

9. Radial (axial) distance

The distance measured in the radial (axial) direction.

10. Contact angle (nominal contact angle)

The included angle between the plane perpendicular to the bearing axis (radial plane) and the resultant force action line (nominal action line) transmitted to the rolling element through the bearing ring or washer.

11. Nominal contact point

The contact point between the rolling element and the raceway surface when the bearing parts are in the normal relative position.

Reference face of a ring (a washer)

The end face of the ferrule (washer) designated by the bearing manufacturer as the datum surface can be used as the datum for measurement.

4、 Torque, load and service life

1. Starting torque

The torque required to start the rotation of one bearing ring or washer relative to another fixed ring or washer.

2. Rotating torque

When one bearing ring or washer rotates, the torque required to prevent the other ring or washer from moving.

3. Radial load

Load acting in the direction perpendicular to the axis of the bearing.

4. Axial load

Load acting in the direction parallel to the axis of the bearing.

5. Static load

The load acting on the bearing when the relative rotation speed of the bearing ring or washer is zero (centripetal or thrust bearing) or when the rolling element has no movement in the rolling direction (linear bearing).

6. Dynamic load

The load acting on the bearing when the bearing ring or washer rotates relative to each other (centripetal or thrust bearing) or when the rolling element moves in the rolling direction (linear bearing).

7. Equivalent load

A general term used to calculate the theoretical load. On a specific occasion, the bearing bears the actual load under the action of the theoretical load.

8. Basic static radial (axial) basic rated static load

Radial static load (central axial static load) corresponding to the total permanent deformation of rolling element and raceway. Under zero load,

if the roller and raceway (roller bearing) are or are assumed to be normal bus (full line contact), under large contact stress, the total permanent deformation at the contact between the rolling element and raceway is 0.0001 times the diameter of the rolling element.

For single row angular contact bearings, the radial rated load is the radial component of the load causing the pure radial displacement of the bearing rings relative to each other.

9. Basic dynamic radial (axial) load rating

Constant radial load (constant central axial load), under which the rolling bearing can theoretically withstand the basic rated life of 1 million revolutions. For single row angular contact bearings, the radial rated load is the component of the load causing the pure radial displacement of the bearing rings relative to each other.

10. Life (of a set of bearings)

A ring or a washer of a bearing or the material of a rolling element before fatigue expansion occurs for the first time

Number of revolutions for another ferrule or washer. The service life can also be expressed by the number of operating hours at a given constant speed.

11. Reliability (referring to bearing life)

The percentage of a group of nearly identical rolling bearings operating under the same conditions that are expected to reach or exceed a specified service life. The reliability of a set of bearings is the probability that the bearing reaches or exceeds the specified life.

12. Rated life

Predicted value of life based on radial basic rated dynamic load or axial basic rated dynamic load.

13. Basic rating life

Rated life associated with 90% reliability.

14. Life factor

In order to obtain the basic rated radial dynamic load or basic rated axial dynamic load corresponding to a given rated life, the correction factor applicable to the equivalent dynamic load.

15. Plummer block with seat bearing

A component of a radial bearing combined with a seat. There is a base plate for installing screws on the support surface parallel to the axis of the bearing.

16. Plummer block housing

Install the seat for rolling bearing.

17. Flange housing

A seat with a radial flange and a screw hole for its installation on the support surface perpendicular to the axis of the bearing.

18. Adapter sleeve

A sleeve with an axial opening with a cylindrical inner hole has a conical outer surface and an external thread at the small end. It is used to install the bearing with taper hole (with lock nut and lock washer) on the shaft with cylindrical outer surface.

19. Withdrawal sleeve

The outer surface of a sleeve with an axial opening of a cylindrical inner hole is conical and the large end is provided with an external thread. It is used to install or remove the bearing with tapered hole on the shaft with cylindrical outer surface (with nut).

20. Lock nut

For the screw nut with cylindrical outer surface and axial groove, use an outer claw of the lock washer and an annular wrench to lock the nut. Used for axial positioning of rolling bearing.

21. Lock washer

Sheet steel washer with many external claws. An outer claw is used to lock the nut, and an inner claw is inserted into the axial groove of the locking sleeve or shaft.

22. Eccentric locking collar

One end is provided with a groove steel ring eccentric relative to the inner hole, which is installed at the equally eccentric extension end of the inner ring of the outer spherical bearing. Rotate the eccentric sleeve relative to the inner ring to fix the inner ring, and then tighten the jacking screw to fix it on the shaft.

23. Concentric locking collar

The steel ring installed on the wide inner ring of the outer spherical bearing is screwed into the hole on the inner ring and in contact with the shaft

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