How to Correctly Install Rolling Bearings —— XSY Bearing

Stop Hammering and Forces of Point Contact to Rolling Bearings

Hammering a rolling bearing during mounting, especially with point contact, causes damage due to the delicate internal design and extremely high contact stresses involved. Let’s break it down technically:

Why It Damages the Bearing

1. Point Load Overstress

Rolling bearings are designed to handle distributed loads through rolling elements (balls or rollers), not sharp impulse forces. A hammer hit introduces a highly concentrated force at one location (point contact), far exceeding material yield limits in that tiny area.

Result:

Micro-cracks, indentations (brinelling), and even raceway deformations.

2. False Brinelling and True Brinelling

If the hit is on a static bearing, it may leave permanent dimples where balls press into the race.

This destroys the smoothness of the raceway → vibration, noise, and premature failure.

3. Internal Misalignment

Hammering on one ring (usually the outer) causes impact force to travel through the rolling elements to the opposite ring.

This misaligns the inner ring vs. outer ring and may cause fractures in cages or rollers.

4. Surface Hardness Breakdown

Bearing raceways and balls are precision-ground and heat-treated (often >60 HRC). These surfaces are brittle on purpose.

A hammer hit introduces plastic deformation → destroys heat-treated layer → early spalling.

5. Cage Deformation or Fracture

Cages are thin and designed only to guide balls or rollers—not absorb axial impact.

Hammering can break or deform cages → misrouting of rolling elements → catastrophic failure.

Best Practice Instead

Use a bearing heater (induction or hot plate) to expand the inner ring thermally, then slide it onto the shaft.

Or use a bearing mounting tool set that applies force evenly to the ring being mounted (inner ring for shaft, outer ring for housing).

Summary

Never hammer bearings into place. Even one improper blow may cut the bearing life to a fraction — from 50,000 hours to 500 hours — and result in unexpected breakdowns in critical machinery.