1. Features and TypesLink BallFeatures of the Link Ball Boots Shank ballHolderFig.1 Structure of Link Ball Model BLStructure and Features With the Link Ball, a highly accurate bearing steel ball used in the spherical area is rst encased in the holder by die cast molding, and then is specially welded with the shank. This unique process enables the mirror surface of the steel ball to be transferred or duplicated on the spherical surface inside the holder to ensure full contact between the ball and the holder. As a result, smooth motion is achieved with a minimum clearance.A22-2

2. Features and Types Features of the Link Ball[Compact Design] Model BL has an adequately rm and yet extremely compact shape because of a highly balanced design. This model is optimal for use in an automobile height sensor or transmission control. [Achieves Sphericity of 0.001 mm] The spherical surface of the shank ball is transferred on the inner surface of the holder while maintaining the sphericity of the bearing steel ball. This allows smooth motion to be achieved with a minimum clearance and provides favorable operability and feel to the link motion.Sphericity: 0.001 mm Sphericity of the spherical surface of the ball shankHOR.x 0.1mmc=mm0.2m1mVER.xRoughness of the spherical surface of the ball shankVER.xHOR.x 0.1mmCut sample of the spherical area of model BLRoughness of the spherical surface of the holderA22-3Link Ball0.4m1mTOKYO SEIMITSU 3. [Two Types of Holder Material] Model BL-A uses the newly developed high strength aluminum alloyA-1 Alloy(see A225 ), which is light and highly resistant to wear. Models BL6 and above and model RBI uses the proven high strength zinc alloy (see A22-6).2AA[High Lubricity] Since models BL and those models attached with boots contain grease, they have high lubricity and increased wear resistance. [Large Hexagonal Bolt Seat] The hexagonal bolt seat of the shank has the same dimensions as the seating surface for small hexagon head bolts in accordance with automotive specifications. This prevents the seating surface from sinking and ensures a stable link motion mechanism. [Equipped with a Boot for Protection against Muddy Water] Use of a boot with high trackability in the ball shank prevents muddy water from entering the spherical area even in a muddy atmosphere. Accordingly, those types equipped with boots are used also in outdoor applications and automobile parts under the chassis. For details, see the muddy water test data ( B22-8 and B22-9).A22-41412Model BL10Model equivalent to similar productA-A cross sectionJaw Span for Wrenching 4. Features and Types Features of the Link BallAlloy [High Strength Aluminum Alloy A-1 Alloy] A-1 Alloy, a newly developed high strength aluminum alloy, is an alloy with A-Zn-Si3 being the main components, is used in the holder of model BL-A.Features of the A-1 Alloy Achieves one of the highest strengths among the existing aluminum die cast alloys. Has yield strength approximately twice that of the commonly used aluminum die cast alloy (ADC 12). Has hardness equal to the high strength zinc alloy and achieves high wear resistance. Achieves speci c gravity less than a half of the high strength zinc alloy to allow signi cant weight saving. Highly corrosion resistance and can be used as an automotive part related to wheel control.Mechanical Properties Tensile strength Tensile yield strength (0.2%) Compressive strength Compressive yield strength (0.2%) Charpy impact Elongation Hardness: 343 to 392 N/mm2 : 245 to 294 N/mm2 : 490 to 637 N/mm2 : 294 to 343 N/mm2 : 0.098 to 0.196 N-m/mm2 : 2 to 3 % : 140 to 160 HVPhysical Properties Speci c gravity Melting point Speci c heat Linear expansion rate:3 : 570 : 793 J/(kgk) : 2210-6Link BallA22-5 5. [High Strength Zinc Alloy] The high strength zinc alloy used in the holders of models BL and RBI has been developed as a bearing alloy by mixing A, Cu, Mg, Be and Ti as well as zinc as the base component. It is excellent in mechanical properties, seizure resistance and wear resistance.Composition Table1 Composition of the High Strength Zinc Alloy Unit: %ItemDescriptionA3 to 4Cu3 to 4Mg0.03 to 0.06Be0.02 to 0.06Ti0.04 to 0.12ZnRemaining portionMechanical Properties Tensile strength Tensile yield strength (0.2%) Compressive strength Compressive yield strength (0.2%) Fatigue strength Charpy impact Elongation Hardness: 275 to 314 N/mm2 : 216 to 245 N/mm2 : 539 to 686 N/mm2 : 294 to 343 N/mm2 : 132 N/mm2107 (Schenk bending test) : 0.098 to 0.49 N-m/mm2 : 1 to 5% : 120 to 145 HVPhysical Properties Speci c gravity Melting point Speci c heat Linear expansion rate: 6.8 : 390 : 460 J/(kgk) : 2410-6Wear ResistanceAmsler wear-tester Test piece rotation speed Load Lubricant: 185 min-1 : 392 N : Dynamo oil80 Wear loss (mg)The wear resistance of the high strength zinc alloy is superior to that of class-3 brass and class-3 bronze, almost equal to that of class-2 phosphor bronze.THK high strength zinc alloy 60 Class-3 bronze Class-3 brass 40 20 0Class-2 phosphor bronze 1020 30 40 50 60 70 80 90 100 Distance (km) (load:392N)Fig.2 Wear Resistance of the High Strength Zinc AlloyA22-6 6. Features and Types Features of the Link BallHow Load Directions Are Called Regardless of the shape, the direction of the load applied to the Link Ball is called axial direction if it is parallel to the axis of the ball shank, and radial direction if it is perpendicular to the axis.Pushing Load and Pulling Load Of the loads applied in the axial direction, the load in the direction of the ball shank being pressed toward the holder is called pushing load and the load in the direction of the ball shank being pulled from the holder is called pulling load. Axial direction Pulling loadPushing loadBall shank HolderRadial directionDirection of applied load The following table shows the load application direction of each model. Avoid using the product in a different load application direction. Failure to do so may damage the product. Model No.Axial directionModel BLModel BL-ARadial directionModel RBILink BallA22-7 7. Types of the Link Ball Types and FeaturesModel BLSpeci cation TableA22-12The holder made of high strength zinc alloy is connected perpendicularly to the shank incorporated with a ball. With a grease pocket formed on the top and bottom of the spherical area, this model achieves high lubricity and high wear resistance.Model BLModel BL-A (supported models: BL4A, BL5A only)Speci cation TableA22-12The holder is connected in perpendicular to the shank, which comprises a male thread specially welded with a highly accurate steel ball. With a grease pocket formed on the top and bottom of the spherical area, this model achieves high lubricity and high wear resistance. Use of the A-1 alloy in the holder significantly reduces the weight.Model BL-AA-1 Alloy, a high strength aluminum alloy newly developed for the Link Ball, has yield strength approximately twice that of the commonly used aluminum die cast material ADC 12, and its strength and wear resistance are equivalent to the high strength zinc alloy. With its speci c gravity less than that of the high strength zinc alloy, model BL-A is optimal as an automotive part that requires lightweight, high strength, high corrosion resistance and high wear resistance.A-1 alloyTensile strength 0.2% yield strengthADC12100200300400500 2Tensile strength (N/mm ) Fig.3 Tensile Strength and Yield Strength of THK A-1 Alloy and ADC 12A22-8 8. Features and Types Types of the Link BallModel RBISpeci cation TableA22-14With this Link Ball model, the high strength zinc alloy is used in its holder, and the mounting bolt and the holder are arranged on the same axis, allowing this model to receive an axial load. Since grease is contained in the boot, this model achieves high lubricity and high wear resistance.Model RBILink BallA22-9 9. Point of SelectionLink BallSelecting a Link Ball The selected bearing must meet both the permissible load obtained from equation (1) and the dynamic load capacity obtained from equation (2). [Permissible Load P] The yield-point strength indicated in the speci cation tables refers to the mechanical strength of the bearing. For model BL, the yield-point strength indicates the strength when a load is applied to the ball shank in a radial direction. For model RBI, it indicates the strength when a load is applied to the ball shank in an axial direction with respect to the holder. (For the load direction, see A22-7.) Table1 Safety Factor (fS)Type of loadLower limit of fSConstant load in a constant direction2 to 3Fluctuating load in a constant direction3 to 5Load in varying directions5 to 8According to the type of the load, select a bearing that satis es the following equation from a mechanical strengths viewpoint.PPk fSP Pk fS: Permissible Load : Yield-point strength : Safety factor(1)(N) (N) (see Table1)[Dynamic Load Capacity Cd] The dynamic load capacity (Cd) refers to the upper limit of load that the spherical area of the Link Ball can receive without showing seizure while the Link Ball is rotating or oscillating. The dynamic load capacity is obtained from the following approximation formula using the static load capacity (CS) (note) indicated in the dimensional table.Cd = Cd Cs nCS 3n(2): Dynamic load capacity : Static load capacity : Revolutions per minute(N) (N) (min1)Note) Static load capacity (CS) refers to the value obtained by multiplying the projected area on the spherical section by the permissible surface pressure, and is used to obtain the dynamic load capacity.A22-10 10. Point of Selection Selecting a Link BallLink BallA22-11 11. Model BL and Model BL-A 2S1 1M d2 d4M1 D1S1M2 DaL2 L1 LOuter dimensions Model No.ThreadedLength Diameter HeightS1Holder dimensions L1L2D1D2W 0 0.3LDMJIS Class 2BL 4DA24.51320M40.718847.59.58BL 5DA34.51526.7M50.82715491210BL 6D381632.6M6130165101311BL 8D45.51938.6M81.253619612.51614BL 10D55.52546.3M101.254323714.51917BL 10BD55.52552.3M101.54323714.51917BL 12D64.52952.7M121.255026817.52219BL 12BD64.52959.7M121.755026817.52219BL 14D743468.4M141.5573010202522BL 14BD743474.4M142573010202522BL 16D833874M161.5643411222724BL 16BD833880M162643411222724Note) Model BL-A is only available in size 4 and 5.[Material] Holder Ball shankBoot[Spherical Clearance] : A-1 alloy (BL4 to 5) (see A22-5) : High strength zinc alloy (BL6 to 16) (see A22-6) : Lightly Carburized Carbon Steel Ball: 650 Hv or higher Shank S35C (20 to 28 HRC) Chromate treatment : NBR special synthetic rubberRadial direction Axial direction: 0.02 to 0.06mm : 0.3mm or less[Tolerance of the Mating Hole of the Ball Shank] H10 is recommended.Model number codingBL6 D L Model number With boot attached Screw symbolA22-12Screw symbolNo symbolLHolder unit set screw Right-hand Left-hand Ball shankTo download a desired data, search for the corresponding model number in the Technical site.Right-handhttps://tech.thk.com 12. D2BWW DUnit: mmApplied Yield-point Ball diam- Permissible tilt angles static load strength eterBall shank dimensions d2M1h91M2Hexagon BDa20 0.30.3CsPkNd4Mass gN4157678.17.9384045101370752110889.29.52540647022501262611111011.611.11240990039202683114121213.812.74012500657049103717151416.215.87540183001130087104317211416.215.87540183001130090124219171719.619.05402670016400143124919241719.619.05402670016400148145621.5221921.922.225403640019800235146221.5281921.922.225403640019800245166023.5232225.422.225303640026900315166623.5292225.422.225303640026900325[Lubrication]It indicates the strength in the direction shown in the gure below.Lithium soap group grease No. 2 is contained in the boot and the cap.[Identi cation of Left-hand Thread] Radial directionIf the female threading is left-handed, its identi cation depends on the marking.ThreadedIdenti cation Cap markingRight-handLeft-handL markPKA22-13Link Ball[Yield-Point Strength] 13. Model RBI D1 d2 D22 W1Outer dimensions Model No.ThreadedLength DiameterS1Shaft diameterHolder dimensions L1L2D1D2Wd20 0.3h9LDJIS Class 2RBI 5D4617M50.82441291195RBI 6D55.220M61285151013116RBI 8D6524M81.253251612.516148RBI 10D74.528M101.25356.51815191710RBI 10BD80.528M101.5356.51815191710RBI 12D8432M121.25406.52017.5221912RBI 12BD9132M121.75406.52017.5221912RBI 14D10336M141.54582520252214RBI 14BD10936M1424582520252214RBI 16D11240M161.55082722272216RBI 16BD11840M1625082722272216[Material] Holder Ball shank Boot[Spherical Clearance] : High strength zinc alloy (see A22-6) : Bearing steel ball Hardness: 650 Hv or higher Shank S35C Chromate treatment : NBR special synthetic rubberRadial direction Axial direction: 0.03mm or less : 0.1mm or less[Tolerance of the Mating Hole of the Ball Shank] H10 is recommended.Model number codingRBI10 D L Model number With boot attached Screw symbolA22-14Screw symbolNo symbolLHolder unit set screw Right-hand Left-hand Ball shankTo download a desired data, search for the corresponding model number in the Technical site.Right-handhttps://tech.thk.com 14. DaS1S1 d 5 d4W D L2 1M2 L1M1 LUnit: mmBall shank dimensions M1M21W1Boot d4Ball Permissible diameter tilt anglesd5Da20 0.30.3Applied static loadYield-point Mass strengthTensile Cs NCompressive Cs NPkgN22118792011.1122556901140028402527.212.2118102012.72574501490037304033161210122415.87525117002320058807539.519.51511143019.05251680033500843012045.519.52111143019.05251680033500843012344211717193222.2252522800456001140018551212417193222.225252280045600114001905823.52217193825.4172980059600149002756423.52817193825.4172980059600149002806225.52319224425.4172980059600149003606825.52919224425.417298005960014900370Note) The permissible tilting angle of types without boot are greater by approximately 5 .[Yield-Point Strength][Lubrication]It indicates the strength in the direction shown in the gure below.Lithium soap group grease No. 2 is contained in the boot.[Identi cation of Left-hand Thread]PKA22-15Link BallIf the female threading is left-hand, symbol L is added. The actual product is marked with symbol L on the holder.Axial direction 15. Point of DesignLink BallPermissible Tilt Angles The permissible tilting angles of Link Ball models are indicated in the corresponding speci cation tables. Note) If the permissible tilt angle is exceeded, it may cause serious damage to the holder or the boot. Be sure to use the Link Ball within its permissible tilt angle.Example of Installation [Comparison of THK Link Ball and the Conventional Rod End] Washer ShaftFlangeTHK model BLConventional Rod End model PHSSine it has a shaft, model BL can easily be installed (especially useful for rod assembly). Because of the improved shape of the boot lip, the spherical area is protected from muddy water even in a muddy atmosphere. Since it contains grease, it can be used without further lubrication. (with the boot attached) Unlike the conventional type, which has a clearance between the shaft and the inner circumference of the inner ring and cannot be xed completely, model BL has minimum distortion and high rigidity since the shank is integrated with the ball. [Examples of Installing Model RBI] Joint for cylinder end metal fitting ForceSuspending a light objectConnecting a rod in the axial direction ForceForce ForceRotation support RotationA22-16 16. Model No.Link BallModel Number Coding Model number con gurations differ depending on the model features. Refer to the corresponding sample model number con guration. [Link Ball]Models BL and RBIBL12 D L Model No. With boot attached Machine screw thread direction No symbol: Right hand (standard) L: Left handScrew symbolsBall shank Holder unit set screwHolder unit set screw Ball shankNo symbolLRight-handLeft-handRight-handLink BallA22-17 17. Precautions on UseLink Ball[Service Temperature] The service temperature of the Link Ball series is basically between -20 and 80. If the service temperature exceeds this range, contact THK. (see examples of testing the product at temperature other than the above service temperature range on B22-8 to B22-9) [Handling] Dropping or hitting the Link Ball may damage it. Giving an impact to it could also cause damage to its function even if the product looks intact. [Lubrication] (1) Lithium soap group grease No. 2 is contained in all boots and can be used without further greasing. (2) Do not mix lubricants of different physical properties. [Precautions on Use] (1) Do not use the product in the manner that the permissible tilting angle is exceeded since doing so may damage the product. (2) When using the product in locations exposed to vibrations or an impact load or in a special environment such as a clean room, vacuum and low/high temperature, contact THK in advance. (3) Entrance of foreign material such as dust between the holder and the inner ring may cause damage or functional loss. Prevent foreign material, such as dust and cutting chips, from entering the product. (4) Model BL is designed for use under loading in radial direction, while model RBI is designed for use under loading in axial direction. [Storage] When storing the Link Ball, avoid high temperature, low temperature and high humidity.A22-18