EngineeringPerformance CriteriaThe following performance criteria relates to the use, installation andspecification of Thomson <strong>Ball</strong> <strong>Bushing</strong>* bearings. Each performancecriteria plays an important role in maximizing system effectivenessand life.Figure 1Phone: 1-800-554-8466Website: www.thomsonballbushing.comHardenedPrecision RingDynamic Load CapacityThe Dynamic load capacity of a <strong>Ball</strong> <strong>Bushing</strong> bearing is determinedby the reaction between the rolling elements and the inner and outerrace. The rolling elements in a <strong>Ball</strong> <strong>Bushing</strong> bearing are a series ofhardened and precision ground bearing balls. The inner race is ahardened and precision ground 60 Case LinearRace.RetainerDouble Track<strong>Bearing</strong> PlateCross-section of <strong>Super</strong> <strong>Smart</strong> <strong>Ball</strong> <strong>Bushing</strong> <strong>Bearing</strong>The outer race can be a hardened and precision ground, ballconforming, steel bearing plate or a hardened and precision groundsteel bearing sleeve. The dynamic load capacity is also affected bythe orientation of the ball tracks, the size of the balls, the shape ofthe ball conforming groove, the number of balls that are in loadcontact and more.Since the introduction of the <strong>Ball</strong> <strong>Bushing</strong> bearing in 1945, DanaherMotion has designed and developed <strong>Ball</strong> <strong>Bushing</strong> bearing productsthat have continuously achieved dramatic increases in dynamic loadcapacity and life. Our most recent innovation is the <strong>Super</strong> <strong>Smart</strong> <strong>Ball</strong><strong>Bushing</strong> bearing which has six times the dynamic load capacity or216 times greater life than the traditional <strong>Ball</strong> <strong>Bushing</strong> bearing.Figure 2Precision groundbearing platePrecision groundbearing ballsThis increase in load capacity was achieved by maximizing the loadreaction between the inner and outer races. This break-through inload capacity rivals that of linear guides while still retaining theadded benefits of the RoundRail* Advantage.The dynamic load capacity of all Thomson <strong>Ball</strong> <strong>Bushing</strong> bearings isbased on a L 10 life of two million inches of travel. The dynamic loadcapacity can be affected by the orientation of the bearing withrespect to the load or the direction of the applied load. A polar graphis included with each product specification to assist you in maximizingthe dynamic load capacity as well as the performance of the<strong>Ball</strong> <strong>Bushing</strong> bearing. To determine the actual dynamic load capacityenter the polar graph with the applied load direction until it intersectsthe polar curve. Next, multiply the proper correction factor by thedynamic load capacity listed in each product specification table.Figure 3Cross-section of XR <strong>Ball</strong> <strong>Bushing</strong> <strong>Bearing</strong><strong>Bearing</strong>Plate<strong>Ball</strong>sCross-section of <strong>Super</strong> <strong>Ball</strong> <strong>Bushing</strong> <strong>Bearing</strong>Polar GraphK 0Figure 4Hardened andPrecision GroundSleeveRetainerCross-section of Precision Steel <strong>Ball</strong> <strong>Bushing</strong> <strong>Bearing</strong>Page 132©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.
Phone: 1-800-554-8466Website: www.thomsonballbushing.comCoefficient of FrictionThe coefficient of friction of Thomson <strong>Ball</strong> <strong>Bushing</strong>* bearings rangesfrom 0.001 to 0.004. There are two components of the coefficient offriction, the rolling or operating friction and the static or breakawayfriction.Coefficient of Rolling FrictionThe rolling coefficient of friction is measured by the force required tooperate the <strong>Ball</strong> <strong>Bushing</strong> at a constant rate of travel. The formula fordetermining frictional resistance during operation is as follows:P f = P x f rWhere,P f = Frictional resistance (lbf)P = Resultant of externally applied loads (lbf)f r = Coefficient of rolling frictionThe following table describes the coefficient of rolling friction of <strong>Ball</strong><strong>Bushing</strong> bearings operating on Thomson 60 Case* LinearRace*.These values are grouped according to the number of ball circuits ineach bearing. Friction coefficients are constant among bearingshaving three and four ball circuits, but slightly less for bearings withfive or six ball circuits. A dry <strong>Ball</strong> <strong>Bushing</strong> bearing has the lowestcoefficient of friction due to the complete absence of lubricantsurface tension effects. Values for grease lubrication ranges from100% greater in the smaller sizes to 20% to 50% greater in thelarger sizes. Oil lubrication (medium/heavy, viscosity 64 cs @ 100ºF)achieves frictional values slightly higher than those for greaselubrication.<strong>Ball</strong> <strong>Bushing</strong> bearing coefficients of rolling friction (f r )Load in % of Rolling Load Rating<strong>Bearing</strong>I.D.1/4, 3/8,1/2, 5/83/4, 11 1/4thru 45/8 thru1 1/2Numberof <strong>Ball</strong>Circuits3 & 45610Conditionof(for 2,000,000 inches of travel)Lubrication 125% 100% 75% 50% 25%No Lube .0011 .0011 .0012 .0016 .0025Grease Lube .0019 .0021 .0024 .0029 .0044Oil Lube .0022 .0023 .0027 .0032 .0045No Lube .0011 .0011 .0012 .0015 .0022Grease Lube .0018 .0019 .0021 .0024 .0033Oil Lube .0020 .0021 .0023 .0027 .0036No Lube .0011 .0011 .0012 .0014 .0019Grease Lube .0016 .0016 .0017 .0018 .0022Oil Lube .0018 .0018 .0019 .0021 .0027No Lube .0011 .0011 .0012 .0013 .0018Grease Lube .0014 .0014 .0015 .0016 .0019Oil Lube .0016 .0016 .0017 .0019 .0025Coefficient of Static FrictionThe coefficient of static or breakaway friction is measured by theforce required to initiate <strong>Ball</strong> <strong>Bushing</strong> bearing movement.The formula used to determine static frictional resistance is:EngineeringSeal DragAnother variable that affects the frictional resistance in a <strong>Ball</strong><strong>Bushing</strong> bearing system is seal drag. When seals are used to retainlubricant or to prevent entry of foreign particles, frictional resistancemust be taken into account for determining total frictional drag. Inapplications where contamination is minimal, the seals can beremoved to reduce frictional drag. In highly contaminatedapplications, seals, wipers and or scrapers are used to minimize theingress of contamination into the bearing. This protective measureadds to the frictional drag of the bearing system. There is a fine linebetween minimizing frictional drag and maximizing contaminantprotection which is controlled by the addition or removal of seals,wipers or scrapers. In applications that require low frictional drag inhighly contaminated environments, contact Thomson applicationengineering.LubricationAll Thomson <strong>Ball</strong> <strong>Bushing</strong> bearings require a small amount of greaseor oil to operate. For most applications, lubricant is recommendedto prevent wearing and rusting of the bearing surfaces. When linearspeeds are high, a light oil should be used and the bearing shouldbe prevented from running dry for a prolonged period of time. Amedium to heavy oil or light grease has greater adhesion propertiesthat afford longer bearing protection and minimize sealing problems.The numerous built-in pockets in the <strong>Ball</strong> <strong>Bushing</strong> bearing retainerallow grease to be stored for an extended period of time. Thoughnot generally recommended, in some lightly loaded, low speed andhighly contaminated applications, <strong>Ball</strong> <strong>Bushing</strong> bearings have beenused without lubrication. For these types of applications contactThomson application engineering.All Thomson <strong>Ball</strong> <strong>Bushing</strong> bearings are shipped with a rustpreventative oil. It is recommended that you lubricate the <strong>Ball</strong><strong>Bushing</strong> bearing prior to installation and periodically duringoperation to assure that the <strong>Ball</strong> <strong>Bushing</strong> bearing does not run dry.For periodic relubrication, most Thomson <strong>Ball</strong> <strong>Bushing</strong> Pillow Blocksare equipped with an access for lubrication.Danaher Motion can provide a specially formulated lubricant,specifically developed to meet a broad range of linear bearingapplications. Thomson LinearLube* lubricant is a synthetic lubricantthat utilizes suspended Teflon ® in a specially formulated compound.LinearLube lubricant provides excellent performance characteristicsin a wide range of applications. It is FDA listed, non-polluting andnon-corrosive. LinearLube lubricant will not stain and adheres tightlyto parts forming a virtually water resistant barrier.• Maintains properties in operating temperatures from –65ºF to 450ºF• USDA Rated HL (Non-Toxic)• Will not oxidize in use• 100% water resistantP f = P x f 0where f 0 = Coefficient of static frictionThe values for the coefficient of static friction or breakawayfriction are not measurably affected by the number of ballcircuits in the bearing or by the lubrication condition.<strong>Ball</strong> <strong>Bushing</strong> bearing coefficients of static friction (f o )Load in % of Rolling Load Rating125% 100% 75% 50% 25%.0028 .0030 .0033 .0036 .0040©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.Page 133* Trademark of Danaher Motion. DANAHER MOTION is registered in the U.S. Patent and Trademark Office and in other countries.
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