Internal Geometry – Roller Bearings by New Hampshire Ball Bearing

Search

Have a technical question or need design assistance?

Fill out and submit a technical request form.

Internal Geometry – Roller Bearings

Radial Play | Roller End Play | Free Angle of Misalignment | Calculations

When establishing the free state internal bearing geometry for roller bearings, the specific bearingapplication details must be carefully considered. These include the bearing loads (radial, axial andmoment), speeds, operating temperature range, the specific geometry of the housing and shaft,their fits and the materials of which they are made.

Proper bearing function is dependent on all of these variables. The extremes of each variable mustbe accounted for in the bearing design to ensure that the maximum and minimum installed internalbearing geometries result in optimal running conditions and maximum bearing life. Consult withNHBB’s Applications Engineering department for assistance with these special design details.

Radial Play

Radial play in roller bearing is similar to radial play in ball bearings. Like ball bearings,roller bearings are assembled with a slight amount of looseness between the rollers andraceways. This looseness, referred to as radial play, is defined as the maximum distancethat one bearing ring can be displaced with respect to the other in a directionperpendicular to the bearing axis when the bearing is in an unmounted state (shownhere).

Some general statements can be made about roller bearing radial play:

Roller bearings are used for support of predominantly radial loads. Minimal thrustloading is tolerable, with a general guideline being 10% of the radial load.

1.

Ideally, a roller bearing will perform best with a minimum installed radial play. This ensures that the load isdistributed among the maximum number of roller elements, thereby minimizing the stresses.

2.

Radial play is affected by any interference fit between the shaft and bearing I.D. or between the housing andbearing O.D.

3.

back to top

Roller End Play

With roller bearings, roller end play (a.k.a. axial play or roller to guide flange clearance) is completelyindependent of radial play. Roller end play is the maximum relative displacement of the roller element withinthe confines of the double guide flanged (u-shaped) ring. Close attention and control of end play isrequired to manage roller skewing and to provide for optimum tracking at all loads and speeds.

back to top

Free Angle of Misalignment

Roller bearings have some capacity for misalignment. As a result of the previously describedlooseness, or play, which is purposely permitted to exist between the bearing components, the innerring can be tilted a small amount in relation to the outer ring. This displacement is called free angle ofmisalignment. The amount of misalignment allowable in a given roller bearing is determined by itsradial play, end play, guide flange angle and roller element geometry, namely the roller flat length andcrown radius values (turn to Roller Bearing Features for more information). The misalignmentcapability of a roller bearing can have positive practical significance because it enables the bearingto accommodate small dimensional variations that may exist in associated shafts and housings. Theperformance of a misaligned roller bearing will be degraded to a certain extent, but for slight misalignments under

Internal Geometry – Roller Bearings by New Hampshire Ball Bearing http://nhbb.com/reference/ball-roller-bearings/internal-geometry-ro...

1 of 3 10/20/2013 1:36 PM

http://nhbb.com/reference/ball-roller-bearings/internal-geometry-ro

reasonably light loads, the effects will not be significant in most cases. In general, the misalignment a bearing issubjected to should never exceed the bearing’s free angle of misalignment.

back to top

Calculating Radial Play, Axial Play and Contact Angle

Radial PlayPD = 2Bd (1 – cos β0)PD = 2Bd – √((2Bd)2 – P2

E)

Axial PlayPE = 2Bd sin β0PE = √(4BdPD – P2

D)

Contact Angleβ0 = cos–1 (2Bd – PD / 2Bd)β0 = sin–1 PE / 2Bd

PD = Radial playPE = Axial playβ0 = Contact angleB = Total curvature = (fi + fo – 1)fi = Inner ring curvature*fo = Outer ring curvature*d = Ball diameter

* Expressed as the ratio of race radius to ball diameter.

back to top

ApplicationsOverviewAerospaceDefenseDentalHigh TechMedicalRacing

CapabilitiesOverviewAstro DivisionHiTech DivisionPrecision Divisionmyonic USACEROBEARNew Product Development Center

ProductsOverviewBall BearingsRoller BearingsSpherical BearingsLoader Slot BearingsRod End BearingsSleeve Bearings (Bushings)Airframe Control BearingsCustom Bearings and AssembliesOscimax®

INVINSYS®

Reference CenterOverviewMiniature & Instrument BearingsBall & Roller Bearings


2 of 3 10/20/2013 1:36 PM


Rod Ends, Sphericals, Loader Slots & Sleeve BearingsProduct TablesCatalogs & BrochuresCommon Conversions

AboutOverviewCommitment to QualitySustainability

Sustainability Value StatementsEnergy Management PlanEnvironmental ResponsibilityHealth and SafetyCalifornia Transparency in Supply Chains Act

Press ReleasesNewsletter ArchiveJobs & CareersContact a DistributorContact Us

NHBB Corporate Headquarters9700 Independence AvenueChatsworth, CA [email protected]

© 2013 New Hampshire Ball Bearings, Inc. All rights reserved.


3 of 3 10/20/2013 1:36 PM

mailto:[email protected]


Documents

Internal Geometry – Roller Bearings by New Hampshire Ball Bearing