When selecting bearings for industrial machinery, the primary goal is to avoid premature failure and ensure reliable operation. Key factors include calculating required load ratings, matching bore diameters to shafts, and accounting for operating speed and temperature. This guide breaks down each step with actionable parameters to simplify the process.

How to Calculate Required Bearing Load Rating

Bearing dynamic load rating (Cr) is the maximum load a bearing can handle for 1 million revolutions, the standard life reference. Use the equivalent dynamic load formula: Pe = X*Fr + Y*Fa, where Fr = radial load, Fa = axial load, X = radial factor, Y = axial factor. For deep groove ball bearings, X=0.56 and Y=1.2 for most applications. For example, a conveyor roller with Fr=3500N and Fa=800N gives Pe=0.56*3500 +1.2*800=2920N. Ensure the selected bearing’s Cr exceeds Pe by at least 1.5x; use a 2x multiplier for heavy-duty construction equipment.

How to Match Bearing Bore Diameter to Shaft

Bore diameter must align precisely with the shaft to prevent misalignment and vibration. Measure the shaft’s actual diameter with a micrometer; standard bearing bores follow ISO metric dimensions, e.g., 50mm, 60mm, 70mm. For a 50mm shaft, select a bearing with a 50mm bore. Avoid oversized bores, which cause bearing creep and reduce lifespan. MS Bearings offers metric bore bearings with precision machining within ±0.005mm tolerance, ensuring a tight, stable fit for industrial shafts.

How to Account for Operating Speed and Temperature

High speeds (over 3000 rpm for small bearings) increase friction and heat, requiring low-friction materials like ceramic balls. Temperatures above 120°C demand high-temperature grease and heat-resistant bearing steel. The dn value (bore diameter × rpm) is a critical metric: keep it below 1,000,000 for standard steel bearings. For example, a fan operating at 4500 rpm with a 100mm shaft has a dn value of 450,000, well within the safe range. For extreme heat, use bearings rated for 200°C or higher.

Contact MS Bearings for free technical support when calculating bearing parameters. For project-specific requirements, consult your bearing supplier.

What is the dn value in bearing selection?

The dn value is the product of bearing bore diameter (mm) and rotational speed (rpm), a key metric to determine if a bearing can handle high-speed operations; keep it below 1,000,000 for standard steel bearings.