32008 Taper Roller Bearing , 40x68x21 Bearing For Agricultural / Construction Machinery

Product Introduction of 32008 Tapered Roller Bearing

I. Product Overview

The 32008 tapered roller bearing is a high-precision heavy-duty mechanical component engineered to meet the operational demands of large-medium duty machinery in harsh and complex working conditions. As a key member of the tapered roller bearing series, it has distinct dimensional parameters: an inner diameter (d) of 40mm, an outer diameter (D) of 68mm, and a width (B) of 21mm. Compared with the 32006 model, its dimensional configuration significantly enhances load-bearing capacity, making it suitable for applications requiring efficient handling of heavy radial loads and moderate-to-high axial forces. However, like other tapered roller bearings, it is sensitive to shaft-housing misalignment, requiring precise installation to ensure stable and reliable machinery operation.

II. Structural Design

2.1 Rolling Elements

The 32008 bearing is equipped with larger-sized precisely manufactured tapered rollers than the 32006 model. These rollers are made of high-quality high-carbon chromium bearing steel (GCr15SiMn), which has better hardenability and toughness than GCr15. After strict heat treatment, the rollers achieve a surface hardness of HRC58-64 and a core hardness of HRC30-45, ensuring excellent wear-resistance and impact-resistance. The production process adheres to strict quality control standards, with the roller's dimensional tolerance controlled within P0-P5 class and surface roughness (Ra) ≤0.1μm. The tapered shape of the rollers forms an optimized line contact with the raceways, which further expands the load distribution area compared to the 32006 model. This design effectively reduces local stress concentrations, minimizing the risk of premature wear and extending the bearing's service life under heavy-load conditions.

2.2 Raceways

Both the inner and outer rings of the 32008 bearing feature matched tapered raceways with a larger cone angle than the 32006 model to adapt to higher load requirements. The raceways and tapered rollers form a "cone assembly" structure—when loads are applied, forces are transmitted along the cone generatrices, enabling efficient handling of combined radial and axial loads. The raceways undergo advanced heat-treatment processes, including carburizing, quenching, and tempering, to form a uniform hardened layer with a depth of 2-4mm. This not only ensures a surface hardness of HRC58-64 but also improves the raceways' fatigue strength, allowing the bearing to withstand frequent load fluctuations and harsh operating environments such as high dust, strong vibration, and temperature variations up to 150°C.

2.3 Cage

A high-strength steel cage (usually made of 20# steel or 45# steel) is used to separate and guide the tapered rollers in the 32008 bearing. The cage is precision-machined using CNC equipment, with evenly spaced pockets that fit the tapered rollers perfectly, preventing collision and friction between adjacent rollers during high-speed operation. This ensures smooth and stable rolling motion, enhancing the bearing's overall reliability and efficiency. In advanced designs, the cage surface may be treated with black oxide or nickel plating to improve its corrosion resistance and wear-resistance. Some high-end models even use brass cages (H62 brass), which have better thermal conductivity and impact-resistance, making the bearing suitable for high-temperature (up to 200°C) and high-impact load applications, such as heavy-duty construction machinery.

III. Performance Characteristics

3.1 1 High Radial and Axial Load-Carrying Capacity

The 32008 tapered roller bearing is specifically designed to handle heavy combined radial and axial loads, with a significantly higher load rating than the 32006 model. Its basic rated dynamic load rating (Cr) typically ranges from 95-105kN (varies by manufacturer), and the basic rated static load rating (C0r) ranges from 130-145kN—ideal for heavy-load applications. The bearing's axial load-carrying capacity is determined by its contact angle (typically 15°-20°); a larger contact angle allows it to withstand greater axial forces (up to 40% of the radial load). This makes it a preferred choice for machinery with complex and heavy load conditions, such as heavy-duty automotive drive axles, large-scale gearboxes, and agricultural tractor main transmissions.

3.2 Moderate-Speed Adaptability

While the 32008 bearing can operate at moderate speeds, its tapered roller design (line contact) results in higher friction than ball bearings, limiting its high-speed performance. Its reference speed (under grease lubrication) is typically around 3800-4800 r/min, and the limiting speed (under oil-bath lubrication) reaches up to 5500-6500 r/min—lower than high-speed ball bearings but sufficient for heavy-duty medium-speed applications, such as heavy industrial motors (15-30kW) and conveyor drive systems in mining sites. Proper lubrication is crucial to reducing friction and heat buildup; exceeding the recommended speed range may cause the bearing temperature to rise above 100°C, leading to lubricant degradation and reduced service life.

3.3 Sensitivity to Misalignment and Mitigation

Like other tapered roller bearings, the 32008 is relatively sensitive to shaft-housing misalignment. Even a small misalignment (exceeding 0.3°) can cause uneven loading on the rollers and raceways, resulting in localized wear, increased vibration, and shortened lifespan. To address this, the bearing requires extremely precise installation: the shaft and housing must be aligned using high-precision laser alignment tools, with the radial misalignment controlled within ≤0.03mm and axial misalignment within ≤0.02mm. The inner ring should have an interference fit with the shaft (H7/p6) to prevent slippage under heavy loads, while the outer ring uses a clearance fit with the housing (H7/js6) to allow slight axial adjustment. In applications prone to minor misalignment (e.g., construction machinery working on uneven terrain), auxiliary components such as self-aligning spacers or flexible couplings can be used to compensate.

IV. Application Fields

4.1 Automotive Industry

In the automotive sector, the 32008 bearing is widely used in heavy-duty vehicle drive axles and differential systems, such as medium-heavy trucks (load capacity 10-20 tons), large SUVs, and commercial buses. In drive axles, it supports the vehicle's weight (heavy radial load) while handling large axial forces generated during acceleration, braking, and cornering; in differentials, it ensures smooth power transfer between the engine and wheels, accommodating speed differences during turns. Its high load capacity meets the heavy-duty requirements of these vehicles, which far exceed the capabilities of the smaller 32006 model.

4.2 Industrial Machinery

In general industrial equipment, the 32008 bearing is a core component in large-scale gearboxes (e.g., speed reducers for mining conveyors, mixer gearboxes in construction material factories) and heavy industrial motors (15-30kW). In gearboxes, it withstands large radial forces from gear meshing and axial thrust from gear tooth engagement, ensuring efficient power transmission; in motors, it supports the heavy rotating shaft, maintaining stability even under variable heavy-load conditions. It is also used in heavy-duty textile machinery (e.g., large-scale spinning frame rollers) and printing machinery, where its heavy-load and moderate-speed performance characteristics align with operational demands.

4.3 Agricultural and Construction Machinery

The 32008 bearing is highly suitable for agricultural and construction machinery operating in harsh environments. In large agricultural tractors (80-120 horsepower), it is used in rear axle systems to support the heavy load of the tractor and agricultural implements, while handling axial forces during field operations such as plowing and harrowing; in heavy construction equipment (e.g., medium excavators, loaders), it is installed in rotary joints, hydraulic pump shafts, and wheel hubs, withstanding high-impact loads and strong vibration. Its corrosion-resistant cage design (with anti-rust coatings) and high-temperature resistance enable it to adapt to outdoor harsh conditions, such as muddy farmland, dusty construction sites, and high-temperature working environments of hydraulic systems.

V. Dimensions and Specification Parameters

VI. Maintenance Points

6.1 Lubrication Management

Proper lubrication is critical to the 32008 bearing’s performance and lifespan. For general heavy-load applications, use high-quality lithium-based grease (NLGI 3) with a dropping point ≥200°C, filling 1/3-1/2 of the bearing’s internal space—over-lubrication causes excessive heat buildup, while under-lubrication leads to dry friction and rapid wear. In high-temperature (150-200°C) environments, switch to synthetic grease (e.g., polyurea-based) with excellent high-temperature stability. For high-speed heavy-load applications, adopt oil-bath lubrication using ISO VG 68-100 industrial gear oil. Establish lubrication intervals based on operating conditions: every 2-4 months for normal heavy-load use, and every 1 month for dusty/vibratory/high-temperature environments.

6.2 Regular Inspection

Conduct frequent inspections to detect early signs of wear or damage. Visually check for cracks, corrosion, or abnormal wear (such as raceway pitting, roller spalling) on the ring surfaces and rollers; use a vibration analyzer to monitor vibration levels (normal range: ≤2.5mm/s). If vibration exceeds 4mm/s or the bearing temperature rises above 100°C (under normal load), immediately stop the equipment, disassemble the bearing, and inspect for issues such as misalignment, roller damage, or lubricant contamination. For key equipment (e.g., mining machinery), combine ultrasonic testing every 3 months to detect internal defects that are invisible to the naked eye, ensuring timely maintenance.

6.3 Installation Precautions

During installation, ensure an ultra-clean working environment to prevent dust, metal debris, or other contaminants from entering the bearing—even small particles can cause severe wear under heavy loads. Use specialized tools such as hydraulic presses and bearing mounting sleeves to install the bearing, avoiding hammering or direct impact on the rings, which can deform the raceways and damage the rollers. The inner ring should have an interference fit with the shaft (H7/p6), and the fit tolerance should be checked using a micrometer to ensure it meets requirements. The outer ring uses a clearance fit with the housing (H7/js6) to allow slight axial movement. After installation, use a dial indicator to check the bearing's runout: radial runout should be ≤0.04mm, and axial runout ≤0.02mm.

6.4 Storage Considerations

When not in use, store the 32008 bearing in a clean, dry, well-ventilated warehouse with a temperature of 5-25°C and humidity ≤50%. Keep the bearing in its original sealed anti-rust packaging; if the packaging is damaged, rewrap it with vacuum-sealed anti-rust film and place it in a moisture-proof container. Store the bearing horizontally on a flat, sturdy shelf, and do not stack more than 2 layers to avoid uneven stress on the rollers and raceways, which may cause permanent deformation. Inspect the bearings every 3 months during storage—if rust spots or moisture are found, clean the bearing with clean kerosene, dry it with compressed air, apply a thin layer of anti-rust oil, and repackage it.