Super Smart Ball Bushing Bearing - Hollin Applications

EngineeringPhone: 1-800-554-8466Website: www.thomsonballbushing.comPerformance Criteria ContinuedThe RoundRail AdvantageThe RoundRail* Advantage is the inherent ability of a BallBushing bearing to accommodate torsional misalignment(caused by inaccuracies in carriage or base machining or bymachine deflection) with little increase in stress to bearingcomponents (Figure 4). This important feature to all ThomsonBall Bushing* bearing systems reduces installation time and∆HFigure 4Figure 5cost, while maximizing performance.Ball Bushing Bearing vs. Linear GuideThe major difference between a Ball Bushing bearing and linearguide system is primarily in the design of the inner race. Thelinear guide inner race has two, four or six ground grooves thatguides the carriage and the precision balls. Due to the ballconforming nature of the grooves, the carriage is preventedfrom accommodating torsional misalignment (Figure 5). Iforsional misalignment is introduced to a linear guide system,the component stress increases, reducing life and performance.In a Ball Bushing bearing system the inner race is a hardenedand ground 60 Case* LinearRace*. Due to the lack of groundgrooves, the Ball Bushing bearing system can accommodatetorsional misalignment and operate without added stress tobearing components.60 Case LinearRace/Ball Bushing Bearing Fit-upThere are three basic fit-up conditions of a Ball Bushing bearingand 60 Case LinearRace, clearance, line-to-line and preload. Inmost product sections there are specification tables that detailthe Ball Bushing bearing working bore diameter and 60 CaseLinearRace diameter tolerance as well as the fit-up betweenthem. The clearance, line-to-line and preload conditions areshown by the abbreviation C for clearance, P for preload and.0000 for a line-to-line condition.ClearanceThe clearance between a Super Smart and Super Ball Bushingbearing and a 60 Case LinearRace is a function of the BallBushing bearing working bore diameter and the diameter toleranceof the 60 Case LinearRace. The working bore diameter ofa Super Smart or Super Ball Bushing bearing is a function ofthe housing bore diameter tolerance. In applications where highaccuracy and repeatability is not required, clearance is acceptable.Clearance can be achieved by following the recommendedhousing bore guidelines found in the product specificationsections. To check for a clearance condition, simply rotate the60 Case LinearRace inside the Super Smart or Super BallBushing bearing while installed in a housing bore. If you canfreely rotate the 60 Case LinearRace then a clearance conditionis present.The clearance between the fixed diameter Precision Steel BallBushing bearing and the 60 Case LinearRace is a function ofthe Ball Bushing working bore and the 60 Case LinearRacediameter. When this Ball Bushing bearing is used with therecommended 60 Case LinearRace a clearance condition willalways exist. For more details see the product specificationsections.PreloadIn applications where accuracy and repeatability are critical, theSuper Smart, Super and Precision Steel Ball Bushing bearingscan be adjusted to a preload fit-up. The Super Smart and SuperBall Bushing bearings are inherently adjustable and wheninstalled in a adjustable housing bore a preload condition canbe achieved. In a nonadjustable housing a preload conditioncan be obtained by making the size of the housing bore smalleror by increasing the diameter of the 60 Case LinearRace. Totest for a preload condition in an adjustable or nonadjustablehousing, simply rotate the 60 Case LinearRace inside the BallBushing bearing while it is installed in the housing bore. If aslight drag is felt then a preload condition is present. When anadjustable housing is used the preload can be altered slightly.The Super Smart and Super Ball Bushing bearing are moretolerant to preload than the Precision Steel Ball Bushing bearing.Preload on a Super Smart and Super Ball Bushing bearingshould be a maximum of .001 inch per inch of 60 CaseLinearRace diameter. Preload on a Precision Steel Ball Bushingbearing should be a maximum of .0001 inch per inch of 60Case LinearRace diameter. When all Ball Bushing bearings arepreloaded, extra care must be taken in mounting the 60 CaseLinearRace parallel.Line-to-LineA line-to-line fit-up condition between a Ball Bushing bearingand 60 Case LinearRace is when no clearance or preload ispresent. A line-to-line fit-up can be achieved in an adjustable orfixed diameter housing. For more details see the productspecification sections.Examples of Ball Bushing bearing/60 Case LinearRace Fit-upsBall BushingBearingPartNumberWorkingBoreDiameterRecommendedHousing BoreDiameter (Fixed)ActualWorkingBoreDiameter60 CaseLinearRaceDiameterBall BushingBearing/60 CaseLinearRaceFit UpSUPER 20 1.2500/1.2494 2.0008/2.0000 1.2508/1.2494 1.2495/1.2490 .0018C/.0001PA-203242 1.2500/1.2494 – 1.2500/1.2494 1.2490/1.2485 .0015C/.0004CXA-203242 1.2500/1.2496 – 1.2500/1.2496 1.2495/1.2490 .0010C/.0001CPage 134©2003 Danaher Motion. Printed in the U.S.A. The specifications in this publication are believed to be accurate and reliable.However, it is the responsibility of the product user to determine the suitability of Thomson products for a specific application.While defective products will be replaced without charge if promptly returned, no liability is assumed beyond such replacement.* Trademark of Danaher Motion. DANAHER MOTION is registered in the U.S. Patent and Trademark Office and in other countries.