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    Bearing Standards – Precision Levels and Tolerances

     Sun, 14 Jul, 2019   /    jvnbe123

    What is a standard?
    A standard is a document that specifies requirements for products, services and/or processes, laying down their required characteristics. This helps ensure the free movement of goods and encourages exports. It serves to safeguard people and goods and to improve quality in all areas of life.

    How is it developed?
    Standards are developed by those who have a need and an interest in using them. The broad participation of all stakeholders, a transparent development process and the consensus principle ensure the wide acceptance of a standard.

    Who develops standards for bearings?
    There are several bodies that are recognized throughout the world in terms of bearing standards and nomenclature. They are:

    • ABMA/ANSI (American Bearing Manufacturers Association / American National Standards Institute): In the US, ABMA maintains the standards deemed necessary by its bearing industry member companies. This includes revising existing or proposing and preparing new standards. These standards are then recommended to the ANSI for approval as US national standards. ANSI has a committee consisting of representatives from user organizations, manufacturers, and the US government that are devoted to rolling bearing standards activities.
    • DIN (Deutsches Institut fur Normung): DIN, the German Institute for Standardization, is the independent platform for standardization in Germany and world over. As a partner for industry, research, and society as a whole, DIN plays a major role to support the marketability of innovative solutions through standardization. Their market-oriented standards and specifications promote global trade, encouraging rationalization, quality assurance and environmental protection as well as improving security and communication.
    • JIS (Japanese Industrial Standard): The Japanese Industrial Standards Committee (JISC), Japan’s national standardization body, plays a central role in developing standards in Japan covering a wide range of products and technologies from robots to pictograms.
    • ISO (International Organization for Standardization): Through its members, it brings together experts to share knowledge and develop voluntary, consensus-based, market-relevant International Standards that support innovation and provide solutions to global challenges.

    Tolerance classes for ball bearings were defined by a committee within the ABMA known as the “Annular Bearings Engineers Committee” (ABEC). These tolerances are commonly referred to as ABEC rating or grade. Tolerance classes for roller bearings are covered by the RBEC classifications contained within the same standard.

    The ABEC (and RBEC) tolerance classifications specify both tolerances of size and form for the individual inner and outer rings. The critical features of the rings include the bore (or inner diameter of the inner ring), the outer diameter of the outer ring, the ring widths, and the raceways of each ring. Tolerances of the form include roundness, taper, runout, and parallelism.

    There are five classes from largest to smallest tolerances: ABEC 1, ABEC 3, ABEC 5, ABEC 7, and ABEC 9. The higher ABEC classes provide better precision, efficiency, and the possibility of greater speed capabilities, but do not necessarily allow the components to spin faster. The ABEC rating does not specify many critical factors, such as load handling capabilities, ball precision, materials, material Rockwell hardness, degree of ball and raceway polishing, noise, vibration, and lubricant. Due to these factors, an ABEC 3 classified bearing could perform better than an ABEC 7 bearing. Bearings not conforming to at least ABEC 1 cannot be classified as precision bearings as their tolerances are too loose.

    The scale also works as a guide for consumers to make informed decisions about the type of bearing they desire, despite not knowing factors related to materials, manufacturing, and performance.

    High rated bearings are intended for precision applications like aircraft instruments or surgical equipment. Lower graded bearings are intended for the vast majority of applications such as vehicles, mechanical hobbies, skates, skateboards, fishing reels, and industrial machinery. High ABEC rated bearings allow optimal performance of critical applications requiring very high RPM and smooth operation.

    Bearing Dimensions and Strict Tolerance Levels
    Bearing Dimensions

    Comparison of Tolerance Classifications of National Standards

    StandardApplicable StandardTolerance Class    Bearing Types
    American National Standards Institute (ANSI)ANSI/ABMA Std.20ABEC-1 / RBEC-1ABEC-3 / RBEC-3ABEC-5 / RBEC-5ABEC-7ABEC-9Radial bearings (Except tapered roller bearings)
    American Bearing Manufacturer's Association (ABMA)ANSI/ABMA Std.19.1Class KClass NClass CClass BClass ATapered roller bearings (Metric series)
    ANSI/ABMA Std.19Class 4Class 2Class 3Class 0Class 00Tapered roller bearings (Inch series)
    Deutsches Institut fur Normung (DIN)DIN 620P0P6P5P4P2All type
    Japanese Industrial Standard (JIS)JIS B 1514Class 0,6XClass 6Class 5Class 4Class 2All type
    ISO 492Normal classClass 6Class 5Class 4Class 2Radial bearings
    Class 6X
    International Organization for Standardization (ISO)ISO 199Normal ClassClass 6Class 5Class 4Thrust ball bearings
    ISO 578Class 4Class 3Class 0Class 00Tapered roller bearings (Inch series)
    ISO 1224Class 5AClass 4APrecision instrument bearings

    Table Terminology:
    Bearing Tolerances: It refers to three aspects of accuracy:

    • Dimensional Accuracy: Dimensional accuracy is a measure of the bearing’s external dimensions, For example, bore diameter (d), outer diameter (D), inner ring width (B), and outer ring width (C). The difference between an actual bearing dimension and the nominal or target value is called the dimensional deviation. The most commonly used measures are the single plane mean bore and outer diameter deviations (Admp and ADmp), and the inner and outer ring width deviations (ABs and ACs). These values are governed by industry standard tolerances. Dimensional accuracy is important for determining shaft and housing fits.
    • Machining Accuracy: Machining (or form) accuracy measures the variation in the above example dimensions when a series of measurements is taken on a single bearing and compared to one other. The most common measures are single radial plane bore and outside diameter variation (Vdp and VDp), mean single plane bore and outside diameter variation (Vdmp and VDmp), and inner and outer ring width variation (VBs and VCs). Variation refers to the difference between the largest and smallest measurements in a series, while mean variation refers to the average difference between consecutive measurements.
    • Running accuracy: Running accuracy (or runout) is a measure of the degree of eccentricity (for radial runout) and squareness (for bore and O.D. with side face) of the bearing. Inner and outer ring radial runout (Kia and Kea) are the measures most often used. Running accuracy is important to keep excess vibration and misalignment of the assembly at a minimum.

    Allowable error limitations for the three areas of bearing accuracy have been internationally standardized for many years as tolerance classes. Each tolerance class specifies a group of limits for all the measures of accuracy (varying in proportion to the bearing size). The most recognized standards are compared in the table above (note that each column represents a set of equivalent classes). For the ISO, JIS, and DiN standards, bearings with standard accuracy are classified as class 0. This is then followed by class 6. From there on, decreasing class numbers denote progressively improving accuracy.

    Radial Runout: Radial run-out is the variation of wall thickness in a bearing race. In technical terms, run-out is the measurement of the raceway in which the rolling element rides and how it relates to the outer ring’s outer diameter and the inner ring’s inner diameter as you rotate the bearing 360 degrees. Incorrect run-out can cause a wide variety of issues, depending on the application. For example, if you have a machine designed to create specially aligned holes in a part, incorrect run-out could affect the proper placement of the holes, meaning those holes might not match up with the mating part. In a motor application, you could face issues with vibration or noise.

    Table IA

    Tolerance Class ABEC-1, RBEC-1
    (ISO Class Normal)
    Inner Ring

    Bore Diameter (d)Bore
    Tolerance
    (Δdmp)
    Radial Runout (Kia)Width Tolerance (ΔBS)(Tolerance values in 0.0001 inch)
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    0.62.50.02360.09840-340-16-
    2.5100.09840.39370-340-47-98
    10180.39370.70870-340-47-98
    18300.70871.18110-450-47-98
    30501.18111.96850-4.560-47-98
    50801.96853.14960-680-59-150
    801203.14964.72440-8100-79-150
    1201804.72447.08660-10120-98-197
    1802507.08669.84250-12160-118-197
    2503159.842512.40160-14200-138-197
    31540012.401615.74800-16240-157-248
    Bore Diameter (d)Bore
    Tolerance
    (Δdmp)
    Radial Runout (Kia)Width Tolerance (ΔBS)
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    0.62.50.02360.09840-8100-40-
    2.5100.09840.39370-8100-120-250
    10180.39370.70870-8100-120-250
    18300.70871.18110-10130-120-250
    30501.18111.96850-12150-120-250
    50801.96853.14960-15200-150-380
    801203.14964.72440-20250-200-380
    1201804.72447.08660-25300-250-500
    1802507.08669.84250-30400-300-500
    2503159.842512.40160-35500-350-500
    31540012.401615.74800-40600-400-630

    Table IB

    Tolerance Class ABEC-1, RBEC-1
    (ISO Class Normal)
    Outer Ring

    Outer Diameter (D)Outer Dia. Tolerance
    (Δdmp)
    Radial Runout (Kea)Width Tolerance (ΔBS)
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    2.560.09840.23620-36
    6180.23620.70870-36
    18300.70871.18110-3.56
    30501.18111.96850-4.58
    50801.96853.14960-510
    801203.14964.72440-614
    1201504.72445.90550-716Identical to Width Tolerance (ΔBS) of Inner Ring of the same Bearing
    1501805.90557.08660-1018
    1802507.08669.84250-1220
    2503159.842512.40160-1424
    31540012.401615.74800-1628
    40050015.748019.68500-1831
    50063019.685024.80310-2039
    63080024.803131.49610-3047
    800100031.496139.37010-3955
    Outer Diameter (D)Outer Dia. Tolerance
    (Δdmp)
    Radial Runout (Kea)Width Tolerance (ΔBS)Tolerance values in micrometers
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    2.560.09840.23620-815
    6180.23620.70870-815
    18300.70871.18110-915
    30501.18111.96850-1120
    50801.96853.14960-1325
    801203.14964.72440-1535Identical to Width Tolerance (ΔBS) of Inner Ring of the same Bearing
    1201504.72445.90550-1840
    1501805.90557.08660-2545
    1802507.08669.84250-3050
    2503159.842512.40160-3560
    31540012.401615.74800-4070
    40050015.748019.68500-4580
    50063019.685024.80310-50100
    63080024.803131.49610-75120
    800100031.496139.37010-100140

    Table II A

    Tolerance Class ABEC-3, RBEC-3
    (ISO Class 6)
    Inner Ring

    Bore Diameter (d)Bore
    Tolerance
    (Δdmp)
    Radial Runout (Kia)Width Tolerance (ΔBS)
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    0.62.50.02360.09840-320-16-
    2.5100.09840.39370-32.50-47-98
    10180.39370.70870-330-47-98
    18300.70871.18110-330-47-98
    30501.18111.96850-440-47-98
    50801.96853.14960-4.540-59-150
    801203.14964.72440-650-79-150
    1201804.72447.08660-770-98-197
    1802507.08669.84250-8.580-118-197
    2503159.842512.40160-10100-138-197
    31540012.401615.74800-16240-157-248
    Bore Diameter (d)Bore
    Tolerance
    (Δdmp)
    Radial Runout (Kia)Width Tolerance (ΔBS)
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    0.62.50.02360.09840-750-40-
    2.5100.09840.39370-760-120-250
    10180.39370.70870-770-120-250
    18300.70871.18110-880-120-250
    30501.18111.96850-10100-120-250
    50801.96853.14960-12100-150-380
    801203.14964.72440-15130-200-380
    1201804.72447.08660-18180-250-500
    1802507.08669.84250-22200-300-500
    2503159.842512.40160-25250-350-500
    31540012.401615.74800-30300-400-630

    Table II B

    Tolerance Class ABEC-3, RBEC-3
    (ISO Class 6)
    Outer Ring

    Outer Diameter (D)Outer Dia. Tolerance
    (Δdmp)
    Radial Runout (Kea)Width Tolerance (ΔBS)
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    2.560.09840.23620-33Identical to Width Tolerance (ΔBS) of Inner Ring of the same Bearing
    6180.23620.70870-33
    18300.70871.18110-33.5
    30501.18111.96850-3.54
    50801.96853.14960-4.55
    801203.14964.72440-57
    1201504.72445.90550-68
    1501805.90557.08660-79
    1802507.08669.84250-810
    2503159.842512.40160-1012
    31540012.401615.74800-1114
    40050015.748019.68500-1316
    50063019.685024.80310-2039
    63080024.803131.49610-1824
    800100031.496139.37010-2430
    Outer Diameter (D)(Metric)Outer Dia. Tolerance
    (Δdmp)
    Radial Runout (Kea)Width Tolerance (ΔBS)Tolerance values in micrometers
    mminchallsingle bearingsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    2.560.09840.23620-78Identical to Width Tolerance (ΔBS) of Inner Ring of the same Bearing
    6180.23620.70870-78
    18300.70871.18110-89
    30501.18111.96850-910
    50801.96853.14960-1113
    801203.14964.72440-1318
    1201504.72445.90550-1520
    1501805.90557.08660-1823
    1802507.08669.84250-2025
    2503159.842512.40160-2530
    31540012.401615.74800-2835
    40050015.748019.68500-3340
    50063019.685024.80310-3850
    63080024.803131.49610-4560
    800100031.496139.37010-6075

    Table III A

    Tolerance Class ABEC-5, RBEC-5
    (ISO Class 5)
    Inner Ring

    Bore Diameter (d)Bore
    Tolerance
    (Δdmp)
    Radial Runout (Kia)Width Tolerance (ΔBS)
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    0.62.50.02360.09840-21.50-16-98
    2.5100.09840.39370-21.50-16-98
    10180.39370.70870-21.50-31-98
    18300.70871.18110-2.51.50-47-98
    30501.18111.96850-320-47-98
    50801.96853.14960-3.520-59-98
    801203.14964.72440-42.550-79-150
    1201804.72447.08660-530-98-150
    1802507.08669.84250-640-118-197
    2503159.842512.40160-750-138-197
    31540012.401615.74800-960-157-248
    Bore Diameter (d)
    Metric
    Bore
    Tolerance
    (Δdmp)
    Radial Runout (Kia)Width Tolerance (ΔBS)Tolerance values in micrometers
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    0.62.50.02360.09840-540-40-250
    2.5100.09840.39370-540-40-250
    10180.39370.70870-540-80-250
    18300.70871.18110-640-120-250
    30501.18111.96850-850-120-250
    50801.96853.14960-950-150-250
    801203.14964.72440-1060-200-380
    1201804.72447.08660-1380-250-380
    1802507.08669.84250-15100-300-500
    2503159.842512.40160-18130-350-500
    31540012.401615.74800-23150-400-630

    Table III B

    Tolerance Class ABEC-5, RBEC-5
    (ISO Class 5)
    Outer Ring

    Outer Diameter (D)Outer Dia. Tolerance
    (Δdmp)
    Radial Runout (Kea)Width Tolerance (ΔBS)
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    2.560.09840.23620-22
    6180.23620.70870-22
    18300.70871.18110-2.52.5
    30501.18111.96850-33
    50801.96853.14960-3.53
    801203.14964.72440-44Identical to Width Tolerance (ΔBS) of Inner Ring of the same Bearing
    1201504.72445.90550-4.54.5
    1501805.90557.08660-55
    1802507.08669.84250-66
    2503159.842512.40160-77
    31540012.401615.74800-88
    40050015.748019.68500-99
    50063019.685024.80310-1110
    63080024.803131.49610-1412
    Outer Diameter (D)Outer Dia. Tolerance
    (Δdmp)
    Radial Runout (Kea)Width Tolerance (ΔBS)
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    2.560.09840.23620-55Identical to Width Tolerance (ΔBS) of Inner Ring of the same Bearing
    6180.23620.70870-55
    18300.70871.18110-66
    30501.18111.96850-66
    50801.96853.14960-98
    801203.14964.72440-1010
    1201504.72445.90550-1111
    1501805.90557.08660-1313
    1802507.08669.84250-1515
    2503159.842512.40160-1818
    31540012.401615.74800-2020
    40050015.748019.68500-2323
    50063019.685024.80310-2825
    63080024.803131.49610-3530

    Table IV A

    Tolerance Class ABEC-7, RBEC-7
    (ISO Class 4)
    Inner Ring

    Bore Diameter (d)Bore
    Tolerance
    (Δdmp)
    Radial Runout (Kia)Width Tolerance (ΔBS)
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    0.62.50.02360.09840-1.510-16-98
    2.5100.09840.39370-1.510-16-98
    10180.39370.70870-1.510-31-98
    18300.70871.18110-210-47-98
    30501.18111.96850-2.51.50-47-98
    50801.96853.14960-31.50-59-98
    801203.14964.72440-320-79-150
    1201804.72447.08660-42.50-98-150
    1802507.08669.84250-4.530-118-197
    Bore Diameter (d)Bore
    Tolerance
    (Δdmp)
    Radial Runout (Kia)Width Tolerance (ΔBS)Tolerance values in 0.0001 inch
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    0.62.50.02360.09840-42.50-40-250
    2.5100.09840.39370-42.50-40-250
    10180.39370.70870-42.50-80-250
    18300.70871.18110-530-120-250
    30501.18111.96850-640-120-250
    50801.96853.14960-740-150-250
    801203.14964.72440-850-200-380
    1201804.72447.08660-1060-250-380
    1802507.08669.84250-1280-300-500

    Table IV B

    Tolerance Class ABEC-7, RBEC-7
    (ISO Class 4)
    Outer Ring

    Outer Diameter (D)Outer Dia. Tolerance
    (Δdmp)
    Radial Runout (Kea)Width Tolerance (ΔBS)Tolerance values in 0.0001 inch
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    2.560.09840.23620-1.51
    6180.23620.70870-1.51
    18300.70871.18110-21.5
    30501.18111.96850-2.52
    50801.96853.14960-32
    801203.14964.72440-32.5Identical to Width Tolerance (ΔBS) of Inner Ring of the same Bearing
    1201504.72445.90550-3.53
    1501805.90557.08660-43
    1802507.08669.84250-4.54
    2503159.842512.40160-54.5
    31540012.401615.74800-65
    Outer Diameter (D)Outer Dia. Tolerance
    (Δdmp)
    Radial Runout (Kea)Width Tolerance (ΔBS)
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    2.560.09840.23620-43Identical to Width Tolerance (ΔBS) of Inner Ring of the same Bearing
    6180.23620.70870-43
    18300.70871.18110-54
    30501.18111.96850-65
    50801.96853.14960-75
    801203.14964.72440-86
    1201504.72445.90550-97
    1501805.90557.08660-108
    1802507.08669.84250-1110
    2503159.842512.40160-1311
    31540012.401615.74800-1513

    Table V A

    Tolerance Class ABEC-9, RBEC-9
    (ISO Class 2)
    Inner Ring

    Bore Diameter (d)Bore
    Tolerance
    (Δdmp)
    Radial Runout (Kia)Width Tolerance (ΔBS)Tolerance values in 0.0001 inch
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    0.62.50.02360.09840-10.50-16-98
    2.5100.09840.39370-10.50-16-98
    10180.39370.70870-10.50-31-98
    18300.70871.18110-110-47-98
    30501.18111.96850-110-47-98
    50801.96853.14960-1.510-59-98
    801203.14964.72440-210-79-150
    1201504.72445.90550-310-98-150
    1501805.90557.08660-320-98-150
    1802507.08669.84250-320-118-197
    Bore Diameter (d)MetricBore
    Tolerance
    (Δdmp)
    Radial Runout (Kia)Width Tolerance (ΔBS)Tolerance values in micrometers
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    0.62.50.02360.09840-2.51.50-40-250
    2.5100.09840.39370-2.51.50-40-250
    10180.39370.70870-2.51.50-80-250
    18300.70871.18110-2.52.50-120-250
    30501.18111.96850-2.52.50-120-250
    50801.96853.14960-42.50-150-250
    801203.14964.72440-52.50-200-380
    1201504.72445.90550-72.50-250-380
    1501805.90557.08660-750-250-380
    1802507.08669.84250-850-300-500

    Table V B

    Tolerance Class ABEC-9, RBEC-9
    (ISO Class 2)
    Outer Ring

    Outer Diameter (D)Outer Dia. Tolerance
    (Δdmp)
    Radial Runout (Kea)Width Tolerance (ΔBS)
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    2.560.09840.23620-10.5
    6180.23620.70870-10.5
    18300.70871.18110-10.5
    30501.18111.96850-1.51
    50801.96853.14960-1.51.5Identical to Width Tolerance (ΔBS) of Inner Ring of the same Bearing
    801203.14964.72440-22
    1201504.72445.90550-22
    1501805.90557.08660-32
    1802507.08669.84250-33
    2503159.842512.40160-33
    31540012.401615.74800-43
    Outer Diameter (D)Outer Dia. Tolerance
    (Δdmp)
    Radial Runout (Kea)Width Tolerance (ΔBS)Tolerance values in 0.0001 inch
    mminchallsingle bearingpaired bearings
    overincl.overincl.highlowmax.highlow
    2.560.09840.23620-2.51.5Identical to Width Tolerance (ΔBS) of Inner Ring of the same Bearing
    6180.23620.70870-2.51.5
    18300.70871.18110-42.5
    30501.18111.96850-42.5
    50801.96853.14960-44
    801203.14964.72440-55
    1201504.72445.90550-55
    1501805.90557.08660-75
    1802507.08669.84250-87
    2503159.842512.40160-87
    31540012.401615.74800-108


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