72 Series — Heavy-Duty Angular Contact Ball Bearings
Maximum Rigidity and Load Capacity for Demanding Machining Applications
The 72 series features the heaviest cross-section in our angular contact bearing range, engineered for machine tool spindle applications where maximum load capacity and system rigidity are paramount. These bearings excel in heavy-duty turning centers, large milling spindles, and applications with high cutting forces where deflection must be minimized.
72 Series — Heavy-Duty Angular Contact Ball Bearings
The 72 Series — Heavy-Duty Angular Contact Ball Bearings delivers industry-leading precision and reliability for demanding machine tool spindle applications. Manufactured in our ISO 9001:2015 certified facility in Luoyang, China — the historic heart of bearing manufacturing — each bearing undergoes rigorous dimensional, running accuracy, and vibration testing before shipment.
The SONGJU B72XX heavy series features the largest cross-section and biggest ball size in our angular contact bearing range, delivering uncompromising load capacity and system rigidity. The thickest rings and largest-diameter balls provide the highest dynamic and static load ratings — typically 2–4× that of equivalent 718-series bearings. The robust ring design minimizes elastic deformation under heavy cutting loads, maintaining dimensional accuracy and surface finish quality even during aggressive roughing with interrupted cuts. For spindle applications where deflection must be absolutely minimized, the 72 series is the definitive choice.
SONGJU B72XX bearings utilize premium GCr15 (100Cr6 / 52100) bearing steel with controlled retained austenite content, ensuring long-term dimensional stability and superior rolling contact fatigue resistance. The reinforced cage design — guided by the outer ring rib for exceptional stability under shock and vibration — is available in phenolic resin, PEEK, or machined brass. Universal face-grinding enables interchangeable DB/DF/DT mounting, with preload classes up to Heavy for maximum spindle stiffness. Available in P5 through P2 precision grades.
72 Series — Heavy-Duty Angular Contact Ball Bearings — Complete Model Parameters
Full model list with α=15° (C) for high-speed and α=25° (AC) for high-rigidity applications. Custom sizes available upon request.
| Model | d | D | B | α=15° (C) — High Speed | α=25° (AC) — High Rigidity | ||||
|---|---|---|---|---|---|---|---|---|---|
| Cr | C0r | Speed | Cr | C0r | Speed | ||||
| 7206 | 30 | 62 | 16 | 23.4 | 18.8 | 23000/37000 | 22.3 | 18.0 | 19000/33000 |
| 7207 | 35 | 72 | 17 | 25.8 | 22.9 | 17000/29000 | 24.5 | 21.9 | 16000/27000 |
| 7208 | 40 | 80 | 18 | 34.1 | 30.9 | 16000/27000 | 32.5 | 29.5 | 14000/23000 |
| 7209 | 45 | 85 | 19 | 35.5 | 33.8 | 15000/25000 | 33.8 | 32.3 | 13000/21000 |
| 7210 | 50 | 90 | 20 | 43.3 | 40.6 | 14000/23000 | 41.3 | 38.7 | 13000/21000 |
| 7211 | 55 | 100 | 21 | 53.6 | 51.1 | 13000/21000 | 51.1 | 48.8 | 12000/19000 |
| 7212 | 60 | 110 | 22 | 55.8 | 56.2 | 11000/18000 | 53.0 | 53.5 | 10000/17000 |
| 7213 | 65 | 120 | 23 | 67.5 | 69.0 | 10000/17000 | 64.2 | 65.8 | 8500/15000 |
| 7214 | 70 | 125 | 24 | 70.2 | 74.6 | 9000/16000 | 66.6 | 71.7 | 8000/14000 |
| 7215 | 75 | 130 | 25 | 72.7 | 80.2 | 8500/15000 | 68.9 | 76.3 | 7500/13000 |
| 7216 | 80 | 140 | 26 | 86.5 | 96.5 | 8000/14000 | 82.1 | 91.9 | 7000/12000 |
| 7217 | 85 | 150 | 28 | 97.4 | 107.5 | 7500/13000 | 92.5 | 102.4 | 6500/11000 |
| 7218 | 90 | 160 | 30 | 121.9 | 131.3 | 7000/12000 | 115.8 | 124.6 | 6000/10000 |
| 7219 | 95 | 170 | 32 | 128.9 | 145.1 | 6500/11000 | 122.5 | 138.3 | 5700/9000 |
| 7220 | 100 | 180 | 34 | 146.2 | 165.9 | 6000/10000 | 138.9 | 158.2 | 5700/9000 |
| 7221 | 105 | 190 | 36 | 164.3 | 118.2 | 6000/10000 | 155.9 | 112.3 | 5400/8500 |
| 7222 | 110 | 200 | 38 | 174.4 | 215.5 | 5600/9000 | 165.5 | 204.7 | 5000/8000 |
All models available in P5, P4, and P2 precision grades. H-prefix = high-speed variant, HQ1 suffix = ceramic hybrid (Si₃N₄ balls). Phenolic, PEEK, or machined brass cages. Contact our engineering team for specific preload and arrangement recommendations.
Configuration Options for 72 Series Angular Contact Ball Bearings
Luoyang Songju offers multiple design variants to meet the full spectrum of spindle design requirements. Below are the standard configuration options available across the 72 series.
Mounting Configuration
Single universally ground bearing (U) for individual mounting, or matched sets: Duplex / D (two bearings), Triplex / T (three bearings), Quadruplex / Q (four bearings) in DB, DF, or DT arrangements.
Universal Matching
Precision face-ground for universal pairing. Interchangeably mount any two bearings of the same size in DB (back-to-back), DF (face-to-face), or DT (tandem) without shims or selective fitting.
Ball Material
Standard: premium GCr15 (100Cr6 / 52100) hardened steel balls. Hybrid option: Si₃N₄ silicon nitride ceramic balls — 40% lighter, lower thermal expansion, superior high-speed performance.
Sealing Options
Open bearings for oil-mist or oil-air lubrication systems. 2RS sealed variant with non-contact rubber seals on both sides for grease-lubricated, contamination-protected applications.
Direct Lubrication
Optional circumferential lubrication groove and radial oil holes in the outer ring for direct oil injection — ensures reliable lubricant delivery at ultra-high speeds.
Preload Classes
Three standard preload levels: Light (L) for maximum speed and minimal heat; Medium (M) for balanced rigidity and speed; Heavy (H) for maximum stiffness in rigid spindle systems.
72 Series Recommended Configuration
For optimal performance in heavy-duty spindle applications, we recommend: Heavy (H) preload + 25° (AC) contact angle + Machined Brass cage. This configuration maximizes spindle stiffness and load capacity for aggressive cutting. For applications balancing load and speed, use Medium (M) preload with 15° (C) contact angle and Phenolic cage.
How to Select 72 Series — Heavy-Duty Angular Contact Ball Bearings
Understanding your application requirements is the first step to specifying the correct bearing configuration. Below are the key selection parameters and recommendations for the 72 series.
1 Determine Contact Angle
Choose for high-speed applications where radial stiffness is the priority. Lower axial stiffness but permits significantly higher rotational speeds. Ideal for grinding spindles and high-speed machining.
Choose when maximum axial rigidity and combined load capacity are required. Higher axial load capacity suits turning centers, milling spindles, and applications with substantial thrust forces.
2 Select Precision Grade
| Grade | ABEC | Radial Runout (max) | Bore Tolerance | Typical Application |
|---|---|---|---|---|
| P5 | ABEC-5 | ≤ 0.004mm | +0 / -0.008mm | General machine tool spindles, pumps |
| P4 | ABEC-7 | ≤ 0.002mm | +0 / -0.005mm | CNC machining centers, precision grinding |
| P2 | ABEC-9 | ≤ 0.001mm | +0 / -0.003mm | Ultra-precision spindles, CMM, optical grinding |
3 Choose Bearing Arrangement
4 Specify Preload and Lubrication
Light preload (L) — Only recommended for applications where thermal expansion accommodation takes priority over stiffness. The 72 series' inherent rigidity means Light preload often suffices for general positioning applications.
Medium preload (M) — Suitable for general milling and turning spindles where the heavy cross-section already provides substantial stiffness.
Heavy preload (H) — Recommended for 72 Series. The heavy cross-section and large ball design are optimized for Heavy preload. Maximizes spindle stiffness for heavy interrupted cutting, large boring operations, and applications where deflection must be minimized at all costs.
72 Series Lubrication Recommendation: The large ball size and heavy cross-section generate more heat than lighter series. Grease lubrication is suitable up to ~6,000 r/min. For higher speeds, oil-air or oil-jet lubrication with cooling is strongly recommended. Direct lubrication via outer ring groove is standard on 72 series bearings above 100mm bore.
Cage Materials, Lubrication & Precision Tolerances
Detailed technical specifications to support proper bearing selection and application engineering for 72 Series — Heavy-Duty Angular Contact Ball Bearings.
Cage Material Selection
| Material | Max Operating Temp | Speed Suitability | Best For | Available Series |
|---|---|---|---|---|
| Phenolic Resin | 120°C | High speed | Standard spindle applications; lightweight, low friction | 718 / 719 / 70 / 72 |
| PEEK | 250°C | Very high speed | High-temperature spindles; superior chemical resistance | 718 / 719 / 70 / 72 |
| Machined Brass | 300°C | Moderate speed | Heavy-duty / shock loads; maximum strength & durability | 70 / 72 (recommended) |
| Polyamide (PA66) | 100°C | Moderate speed | Cost-effective; general industrial, non-spindle use | 70 / 72 |
Lubrication Method Comparison
| Method | Speed Factor (dmN) | Cooling | Complexity | Best Application |
|---|---|---|---|---|
| Grease | Up to 1.0 × 10⁶ | None | Low | Standard spindles, periodic maintenance OK |
| Oil-Mist | Up to 1.5 × 10⁶ | Minimal | Medium | High-speed grinding, continuous operation |
| Oil-Air | Up to 2.0 × 10⁶ | Good | Medium-High | Ultra-high-speed spindles, ceramic hybrids |
| Oil-Jet | Up to 2.5+ × 10⁶ | Excellent | High | Maximum speed; requires oil recovery system |
| Direct Lubrication | +15–20% vs standard | Application-dependent | Medium | Optimizes delivery via outer ring groove & radial holes |
Speed factor (dmN) = pitch diameter [mm] × rotational speed [r/min]. Values are indicative — actual limits depend on bearing size, preload, and cage material.
Precision Grade Tolerance Table (ISO 492)
| Parameter | Symbol | P5 (ABEC-5) | P4 (ABEC-7) | P2 (ABEC-9) |
|---|---|---|---|---|
| Bore deviation (nominal d ≤ 80mm) | Δdmp | 0 / -8 μm | 0 / -5 μm | 0 / -3 μm |
| Bore deviation (80 < d ≤ 180mm) | Δdmp | 0 / -10 μm | 0 / -7 μm | 0 / -4 μm |
| Bore deviation (180 < d ≤ 250mm) | Δdmp | 0 / -15 μm | 0 / -10 μm | 0 / -5 μm |
| OD deviation (nominal D ≤ 150mm) | ΔDmp | 0 / -9 μm | 0 / -6 μm | 0 / -4 μm |
| OD deviation (150 < D ≤ 250mm) | ΔDmp | 0 / -13 μm | 0 / -8 μm | 0 / -5 μm |
| Inner ring radial runout | Kia | ≤ 4 μm | ≤ 2 μm | ≤ 1 μm |
| Outer ring radial runout | Kea | ≤ 5 μm | ≤ 3 μm | ≤ 1.5 μm |
| Axial runout (inner ring face) | Sia | ≤ 5 μm | ≤ 3 μm | ≤ 1.5 μm |
| Width tolerance (all sizes) | ΔBs | 0 / -40 μm | 0 / -25 μm | 0 / -15 μm |
Industries & Applications for 72 Series — Heavy-Duty Angular Contact Ball Bearings
72 Series — Heavy-Duty Angular Contact Ball Bearings are trusted across a wide range of precision industries worldwide. Below are the primary application areas where the 72 series delivers measurable performance advantages.
Heavy-Duty Turning Centers
Large-bore spindle bearings in horizontal and vertical turning centers where heavy interrupted cuts and high metal removal rates are standard production practice.
Large Milling & Boring Spindles
Floor-type boring mills, gantry mills, and large machining centers — the 72 series thickest cross-section resists deflection under extreme tool forces and workpiece weights.
Industrial Gearboxes
Input, intermediate, and output shaft bearings in heavy industrial gear reducers — high load capacity and robust cage design required for shock and reversing loads.
Automotive Assembly Lines
Transfer line spindles and heavy automation axes where reliability, consistency, and minimal maintenance are critical for high-volume production.
Heavy Printing Presses
Large-format printing cylinder support bearings where the 72 series' maximum rigidity ensures consistent impression quality across wide web widths.
Industrial Robots & Positioners
Heavy-payload robot wrist joints and positioner axes — combined load capability and robust design for reliable operation in harsh manufacturing environments.
Engraving & Engraving Spindles
Heavy engraving and die-sinking spindles where cutting forces are moderate but precision must be maintained under continuous operation.
Tool Turret & Tool Post Bearings
CNC lathe tool turret indexing mechanisms and live tooling spindles where compact size, high rigidity, and precise positioning are essential.
Why Choose Luoyang Songju 72 Series — Heavy-Duty Angular Contact Ball Bearings
The 72 series features the heaviest cross-section in our angular contact bearing range, engineered for machine tool spindle applications where maximum load capacity and system rigidity are paramount. These bearings excel in heavy-duty turning centers, large milling spindles, and applications with high cutting forces where deflection must be minimized.
Maximum Load Capacity
Heaviest cross-section delivers the highest dynamic and static load ratings. Built for heavy turning, deep milling, and interrupted cuts.
Superior Rigidity
Largest ball size and thickest rings minimize elastic deformation under load. Critical for maintaining dimensional accuracy during heavy machining.
High Reliability
Robust design with reinforced cage and optimized roller/raceway contact for consistent performance in continuous-duty industrial applications.
Combined Load Capability
Designed to carry significant combined radial and axial loads. 25° contact angle (AC) variant provides maximum thrust capacity.
Multiple Cage Options
Phenolic resin for standard; PEEK for high-speed/high-temp; machined brass for heaviest-duty. Guided by outer ring rib for superior stability.
Long Service Life
Premium GCr15 (100Cr6/52100) bearing steel with controlled retained austenite content ensures dimensional stability and fatigue resistance.
Need 72 Series — Heavy-Duty Angular Contact Ball Bearings?
Tell us your bore size, contact angle, precision grade, preload class, and quantity — our application engineers will respond within 24 hours with a competitive quotation and detailed technical documentation.