Double-direction Thrust Ball Bearing

I. Product Overview​

Double-Direction Thrust Ball Bearings (abbreviated as DDTBB) are a specialized category within the thrust ball bearing family, designed for scenarios requiring heavy bidirectional axial load-bearing, minimal radial load, and simplified bidirectional axial positioning structures. Their core competitiveness lies in the triple characteristics of "single-bearing heavy bidirectional axial load capacity + separable integrated structure + high stability" - through an exclusive design of "central shaft washer + two side housing washers + double-row steel balls", they break the limitation of single-direction thrust ball bearings (which "can only bear unidirectional loads with a single bearing"). A single DDTBB can stably withstand a bidirectional axial rated dynamic load of 2kN-600kN (forward and reverse axial forces can be borne independently without mutual interference). Adopting a separable four-part structure consisting of a shaft washer, upper housing washer, lower housing washer, and double-row ball-cage assembly, it eliminates the need for paired installation of two single-direction thrust ball bearings, saving 40%-60% of installation space. Meanwhile, due to its extremely weak radial load-bearing capacity (only able to bear 1%-3% of the axial load as radial load, requiring pairing with radial bearings such as deep groove ball bearings or cylindrical roller bearings), it accurately matches working conditions where "bidirectional axial forces dominate and radial forces are negligible", completely solving the industry pain points of "complex transmission structures and large space occupation in heavy bidirectional axial load scenarios".​

The inner diameter of these bearings ranges from 10mm to 350mm, the outer diameter from 28mm to 450mm, and the total thickness (sum of upper housing washer, shaft washer, and lower housing washer thickness) from 12mm to 65mm. The limiting speed under grease lubrication is 2,000-12,000 r/min (light-duty models can reach 15,000 r/min). Precision grades are mainly P6 (dimensional tolerance ±8μm) and P5 (dimensional tolerance ±5μm), with P4 grade available for precision scenarios (e.g., high-end machine tool spindles). Classified by steel ball arrangement, they include double-row symmetric models (basic type, no suffix) and double-row enhanced models (multi-row balls, suffix MA). They are suitable for scenarios such as machine tool spindles, large gearboxes, elevator traction machines, and precision instruments - where "bidirectional axial positioning + integrated compact design" is required. The complexity of the equipment transmission structure is reduced by 50%, and space utilization is increased by more than 40%.​

Compared with two paired single-direction thrust ball bearings, DDTBB have a more integrated structure and easier installation (no need to adjust the coaxiality of two bearings) with better bidirectional load consistency. Compared with angular contact ball bearings (paired installation) that can bear bidirectional axial forces, DDTBB have 40%-60% higher axial load capacity of the same size and are 15%-25% cheaper, with no need to consider contact angle matching or installation methods (back-to-back/face-to-face). Covering over 65% of the transmission field dominated by bidirectional axial forces, they are the optimal choice for balancing "bidirectional load requirements, structural integration, and cost control".​

II. Core Structure and Design Features​

1. Precision Structural Composition​

The four core components of DDTBB (central shaft washer, upper housing washer, lower housing washer, double-row ball-cage assembly) are deeply optimized to meet the requirements of "heavy bidirectional axial load-bearing, integrated force transmission, and easy assembly/disassembly", ensuring reliable operation under bidirectional axial force conditions:​

Central Shaft Washer: Adopts a circular disc structure with double working surfaces, with its inner hole in an interference fit with the shaft (fit accuracy H7/k6) and no fit requirement for the outer circle. Both upper and lower working surfaces are precision-machined flat raceways, with a raceway surface roughness of Ra ≤ 0.03μm, a flatness error of ≤ 0.8μm, and a parallelism error of ≤ 0.008mm between the two raceways. The material used is SUJ2 high-carbon chromium bearing steel (20CrNiMo alloy carburized steel is optional for heavy-duty models), which undergoes "integral quenching + ultra-precision grinding" processes. The surface hardness reaches HRC 61-65, and the core hardness is HRC 32-36, ensuring no deformation or cracking under heavy bidirectional axial loads.​

Upper/Lower Housing Washers: Symmetrical in structure, both adopt a circular disc structure with a single working surface, with their outer circles in a transition fit with the housing hole (fit accuracy H7/js6) and no fit requirement for the inner holes. The working surface is a flat raceway, with a parallelism error of ≤ 0.01mm relative to the corresponding raceway of the central shaft washer, ensuring uniform contact with double-row steel balls. The material and processing technology are consistent with those of the central shaft washer, providing synchronized surface hardness and wear resistance to prevent bidirectional load imbalance caused by wear of a single-side housing washer.​

Double-Row Ball and Cage Assembly: Composed of double-row steel balls and an integrated cage, the steel balls are made of GCr15SiMn high-purity bearing steel. Their diameter is designed according to bidirectional load requirements (5mm-16mm for light-duty models, 16mm-32mm for heavy-duty models), processed through "vacuum melting + precision grinding + nano-level polishing" processes, with a roundness error of ≤ 0.12μm and a surface roughness of Ra ≤ 0.015μm. The cage is divided into stamped integrated cages (SPCC steel plate, suitable for medium-low speed scenarios, rotational speed ≤ 6,000 r/min) and solid integrated cages (HPb59-1 brass or PA66 + 30% glass fiber nylon, suitable for medium-high speed scenarios, rotational speed 6,000-12,000 r/min). The cage pockets adopt a "double-row symmetric shallow pocket + positioning boss" design, with a coaxiality error of ≤ 0.01mm between double-row pockets and a clearance of 0.08-0.18mm between pockets and steel balls, preventing steel ball movement and ensuring uniform transmission of bidirectional axial forces.​

2. Key Design Characteristics​

Single-Bearing Heavy Bidirectional Axial Load-Bearing: The combined design of the central shaft washer's double raceways and double-row steel balls enables forward axial forces to be transmitted to the central shaft washer and upper housing washer through the upper row of steel balls, and reverse axial forces to be transmitted to the central shaft washer and lower housing washer through the lower row of steel balls. The bidirectional axial rated dynamic load ranges from 2kN to 600kN (e.g., the 52210 model has a bidirectional axial rated dynamic load of 52kN, and the heavy-duty 52420 model reaches 380kN), which can stably bear heavy loads such as bidirectional cutting thrust of machine tool spindles and bidirectional axial runout force of gearboxes. The bidirectional load capacity can be flexibly adjusted by the diameter and number of steel balls (double-row enhanced models have a 60% higher capacity than basic models).​

Integrated Structure for Space Saving: A single bearing integrates "bidirectional load-bearing function", replacing the combined structure of "two single-direction thrust ball bearings + spacer". Installation space is saved by 40%-60% (e.g., at the machine tool spindle end, where two single-direction bearings originally required 120mm of installation length, DDTBB only require 50mm). Meanwhile, there is no need to adjust the coaxiality of two bearings (avoiding eccentric load caused by coaxiality errors), with a bidirectional load consistency error of ≤ 5%, greatly improving equipment space utilization and operational stability.​

Low Friction and Adaptable Speed: The point-contact design between flat raceways and double-row steel balls results in a low friction coefficient of 0.0012-0.0018 (85% lower than sliding friction bearings) and an operating noise of ≤ 52dB. The limiting speed under grease lubrication is 2,000-12,000 r/min: stamped cage models are suitable for 2,000-6,000 r/min (e.g., elevator traction machines), brass cage models for 6,000-10,000 r/min (e.g., machine tool spindles), and nylon cage models for 10,000-12,000 r/min (e.g., precision instruments), meeting speed requirements of different scenarios.​

Pairing with Radial Bearings: Due to its extremely weak radial load-bearing capacity (only able to bear 1%-3% of the axial load as radial load), it must be paired with radial bearings (e.g., deep groove ball bearings, cylindrical roller bearings) in practical applications - radial bearings bear the radial load of the equipment, while DDTBB bear the bidirectional axial load. The two work synergistically to form a complete "radial + bidirectional axial" load-bearing system, avoiding raceway eccentric wear caused by radial forces and extending service life.​

III. Main Product Models and Classification​

1. Classification by Structural Type (Steel Ball Arrangement)

2. Classification by Precision Grade​

Grade P6: Dimensional tolerance (central shaft washer inner diameter, housing washer outer diameter) ±8μm, raceway flatness ±1μm. Suitable for general precision scenarios (e.g., elevator traction machines, standard gearboxes), with moderate cost and high cost-effectiveness, accounting for over 60% of the market share.​

Grade P5: Dimensional tolerance ±5μm, raceway flatness ±0.5μm. Suitable for medium-precision scenarios (e.g., machine tool spindles, precision instruments), capable of meeting bidirectional axial positioning accuracy of ±0.008mm, accounting for approximately 30% of the market share.​

Grade P4: Dimensional tolerance ±3μm, raceway flatness ±0.3μm. Suitable for high-precision scenarios (e.g., high-end CNC machine tools, aerospace auxiliary equipment), requiring ultra-precision grinding and strict testing (bidirectional load consistency error ≤ 3%), accounting for approximately 10% of the market share.​

3. Classification by Cage Material​

Stamped Steel Plate Integrated Cage: Designation with no suffix (or suffix Z), material of SPCC cold-rolled steel plate. Double-row pockets are integrated through stamping, with low cost and light weight, suitable for medium-low speed, medium-light load scenarios (rotational speed ≤ 6,000 r/min, e.g., small motors, conveyor equipment).​

Brass Solid Integrated Cage: Designation with suffix H, material of HPb59-1 brass. Coaxiality control of double-row pockets is achieved through CNC machining, with high strength and good heat dissipation, suitable for medium-high speed, medium-heavy load scenarios (rotational speed 6,000-10,000 r/min, e.g., machine tool spindles, large fans).​

Reinforced Nylon Integrated Cage: Designation with suffix TN, material of PA66 + 30% glass fiber. After injection molding and precision machining, it has a low friction coefficient and wear resistance, suitable for medium-high speed, light load scenarios (rotational speed 10,000-12,000 r/min, e.g., precision instruments, medical devices).​

IV. Applicable Industries and Typical Applications​

With core advantages of "single-bearing bidirectional load-bearing, integrated structure, and high cost-effectiveness", DDTBB are widely used in industrial fields dominated by bidirectional axial forces. Typical applications include:​

Machine Tool Industry: High-end CNC machine tool spindles (suitable for Model 52212P5/H, brass cage, bidirectionally bearing spindle cutting thrust, paired with cylindrical roller bearings to bear radial load, positioning accuracy ±0.005mm at 8,000 r/min), machining center tool magazine rotating shafts (suitable for Model 52306P6, double-row symmetric type, bearing bidirectional rotating axial force of the tool magazine, compact structure saving space), and lathe lead screw support ends (suitable for Model 52408P5, heavy-duty double-row type, bearing bidirectional transmission thrust of the lead screw, ensuring feed accuracy).​

General Machinery Industry: Output shafts of large gearboxes (suitable for Model 52416MA/P6, double-row enhanced type, bearing bidirectional axial runout force of gears, adapting to 6,000 r/min, stable operation for long periods), centrifugal compressor rotors (suitable for Model 52218P5, medium precision, bidirectionally bearing axial gas thrust of the rotor, paired with deep groove ball bearings to bear radial load), and main shafts of large fans (suitable for Model 52220P6/H, brass cage, bidirectionally bearing axial thrust of fan impellers, operating noise ≤ 48dB).​

Elevator and Lifting Industry: High-speed elevator traction machines (suitable for Model 52214P6, double-row symmetric type, bearing bidirectional lifting/braking axial force of the elevator car, stable operation at 4,000 r/min), slewing mechanisms of tower cranes (suitable for Model 52412MA/P6, double-row enhanced type, bearing bidirectional axial force of slewing, paired with cylindrical roller bearings to bear radial load, strong impact resistance), and elevator door machine drive shafts (suitable for Model 52204P6, small light-load type, bearing bidirectional opening/closing axial force of the door machine, low cost and easy maintenance).​

Precision Instrument and Medical Device Industry: Precision gearboxes (suitable for Model 52206P5, medium precision, bearing bidirectional axial transmission load of gears, ensuring transmission accuracy ±0.01mm), CT scanner rotating frames (suitable for Model 52310P5/TN, nylon cage, bidirectionally bearing axial force of the rotating frame, vibration ≤ 1.2m/s² at 6,000 r/min), and precision surgical robot joints (suitable for Model 52205P4, high precision, bidirectionally bearing axial force of joint rotation, positioning error ≤ 0.003mm).​

Aerospace and Transportation Industry: Auxiliary shafts of aircraft engines (suitable for Model 52207P4, high precision, bidirectionally bearing axial force of the auxiliary shaft, adapting to high-altitude low-pressure environments, high reliability), reducers of new energy vehicles (suitable for Model 52208P6, double-row symmetric type, bearing bidirectional axial runout force of reducer gears, adapting to 8,000 r/min), and high-speed rail traction motors (suitable for Model 52210P5, medium precision, bidirectionally bearing axial electromagnetic force of the motor rotor, paired with deep groove ball bearings to ensure stable operation).

V. Product Advantages Summary
Single set of bidirectional heavy-load bearing, precise fit: 2kN - 600kN of bidirectional axial rated dynamic load, dedicated to bearing bidirectional axial forces, precisely matching the "bidirectional axial force dominant, radial force negligible" working conditions, avoiding performance redundancy of multiple sets of bearings, and achieving high bidirectional bearing efficiency.
Integrated structure, saves space and cost: single set integrates bidirectional bearing function, replacing "two sets of single-direction thrust ball bearings + spacer sleeve" combination, installation space is saved by 40% - 60%, and there is no need to adjust the coaxiality of multiple sets of bearings, reducing the complexity of the equipment transmission structure by 50%, and reducing the overall procurement cost by more than 20%.
Consistent bidirectional bearing performance, stable operation: symmetrical design of the middle shaft ring's double raceways and double rows of steel balls, making the bidirectional bearing error ≤ 5% (P5 grade accuracy), far exceeding the combination of two sets of single-direction thrust ball bearings (error ≤ 15%); friction coefficient as low as 0.0012 - 0.0018, operating noise ≤ 52dB, suitable for a wide speed range of 2000 - 12000 r/min, with strong operational stability.
Easy disassembly and maintenance, low maintenance cost: separable structure (shaft ring, seat ring, cage components can be disassembled separately), installation does not require overall alignment, during maintenance, only worn parts (such as replacing the upper seat ring or lower seat ring) can be replaced separately, improving disassembly efficiency by 60% and reducing maintenance cost by 35%.
Flexible combination, wide application range: can be flexibly combined with deep groove ball bearings, cylindrical roller bearings, etc., forming a "radial + bidirectional axial" complete bearing system, suitable for various scenarios such as machine tools, elevators, machinery, instruments, etc., coverage exceeds 65%, with strong versatility.

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