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At a Glance
Deep groove ball bearing axial load capacity depends on the contact angle that forms between the ball and raceway shoulder. The permissible axial load is typically 0.25 to 0.50 times C0 for pure thrust. When combined radial and axial loads are present, use the equivalent load formula P = X · Fr + Y · Fa. For sustained axial loads above 50% of radial, angular contact bearings deliver longer life.
What Axial Load Means for a Deep Groove Ball Bearing
A deep groove ball bearing carries axial load through a contact angle that forms between the ball and the raceway. Under pure radial load, the ball contacts the raceway at the deepest point of the groove. When an axial force is applied parallel to the shaft, the contact point shifts up the side of the groove wall, creating an angle between the ball-to-race contact line and the radial plane.
Contact Angle
8° to 15°
Standard deep groove
Axial/Radial Ratio
0.25 to 0.50
Pure axial vs radial
Max Permissible
0.5 × C0
Static load limit
The deeper the groove relative to the ball diameter, the larger the potential contact angle and the higher the axial capacity. For a standard deep groove ball bearing with a normal internal clearance, the axial-to-radial load ratio is roughly 0.25 to 0.50. A bearing rated for 10 kN radial dynamic load can typically handle 2.5 to 5 kN of pure axial load. This ratio drops when both radial and axial loads are present simultaneously, which requires an equivalent dynamic load calculation.
How Much Axial Load Can a Deep Groove Ball Bearing Take
Bearing manufacturers publish two axial load ratings: the static safety limit and the dynamic fatigue life limit. The static axial load rating (C0) defines the force that produces a permanent deformation of 0.0001 times the ball diameter at the most heavily loaded contact point. Exceeding C0 permanently damages the raceway.
Equivalent Dynamic Load
P = X · Fr + Y · Fa
Fr = radial load (kN) | Fa = axial load (kN) | X, Y = factors from catalog
For a single row deep groove ball bearing, Y typically ranges from 1.0 to 2.0 depending on the Fa/C0 ratio and the internal clearance class.
Rule of Thumb
When Fa/Fr exceeds 0.5, bearing life drops faster than equations predict because the contact ellipse shifts toward the raceway edge. At Fa/Fr above 1.0, the bearing runs near the shoulder where stress concentration and lubrication breakdown accelerate wear.
For small bore bearings (under 30 mm), the permitted axial load is often limited by the snap ring or shoulder strength rather than the fatigue life of the raceway. A 6204 bearing with C0 = 6.55 kN might have a catalog axial limit of 1.6 kN, well below the 0.5 × C0 guideline, because the shoulder geometry constrains it.
Five Factors That Influence Axial Load Capacity
1. Internal Clearance
C3 or C4 clearance develops a larger contact angle under axial load because the balls have more room to shift. This increases axial capacity but reduces radial stiffness and raises noise. For applications with dominant axial loads, C3 clearance is the standard starting point.
2. Groove Curvature (Osculation)
The ratio of groove radius to ball diameter typically ranges from 0.515 to 0.530. A tighter groove (closer to 0.505) increases axial capacity by providing a steeper contact angle at the shoulder, but raises friction and heat generation. Yuanhe uses 0.515 to 0.520 osculation in standard bearings, balancing axial capacity against operating temperature.
3. Bearing Series
The 62 and 63 series carry higher axial loads than the 60 and 68 series at the same bore size. A 6304 bearing handles roughly 40% more axial load than a 6004 bearing of the same bore, despite similar radial ratings. The larger ball diameter relative to cross section produces a higher contact angle for a given axial displacement.
4. Speed
Centrifugal force on the balls reduces the contact angle at the inner ring as shaft speed increases. At speeds above 50% of the limiting speed, effective axial capacity drops by 10 to 20%. For high-speed spindles, angular contact bearings with a preload are the correct choice.
5. Lubrication
Axial load pushes the contact ellipse toward the edge of the raceway, where lubricant film thickness is thinner. Grease with EP additives or higher base oil viscosity helps maintain separation. For axial loads above 0.3 × C0, oil lubrication is preferred over grease.
When to Move to Angular Contact Bearings
Deep groove ball bearings are the default choice for combined loading when axial loads are moderate and intermittent. Three conditions make angular contact bearings the better option.
| Condition | Deep Groove | Angular Contact |
|---|---|---|
| Fa/Fr consistently above 0.5 | Life drops rapidly | Designed for this range |
| Pure axial load as primary direction | Limited to 0.25 C0 | Full dynamic rating |
| High axial stiffness required | Inherent axial play | Preload removes play |
For OEM applications where the load mix is unclear during the design phase, Yuanhe engineers can review the application data and recommend the right bearing configuration. Send the shaft layout and duty cycle for a bearing selection report.
Need Help Selecting Bearings for Your Application?
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FAQ
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