In an antifriction-type bearing, a rise in temperature is most likely caused by which condition?

• A. Insufficient grease
• B. Excessive run out
• C. Excessive grease
• D. Insufficient run out

Answer: (C)

Too much lubricant in an antifriction bearing causes a temperature rise. When the bearing rotates, the grease in the clearance is sheared and dragged, so excess grease means more viscous resistance and more energy is converted into heat. The extra grease also can trap heat and hinder heat dissipation from the bearing surfaces, allowing temperatures to climb. Over-greasing can also push grease out of the seal, creating contamination and additional friction, further raising temperature. While other issues like insufficient lubrication or misalignment can cause problems, the amount of grease is the most direct and common cause of a noticeable temperature rise in this scenario.