Misalignment & distorted seats (edge loading)
The load path is in the wrong place. Urgency
Not separate ISO modes, but the overheating, seizure, cage and alignment problems that surround them.
What misalignment & distorted seats (edge loading) looks like
- Wear or spalling concentrated on one side of the raceway instead of centred
- A path that sweeps from one edge of the stationary ring to the other
- Two load zones 180° apart when the housing bore is oval or pinched
Rotec AI schematic illustration. It shows the typical pattern and is not a photograph of a real bearing.
How misalignment & distorted seats (edge loading) develops
If shaft and housing are not truly aligned (a bent shaft, a bore that is not square, soft foot, deflection) the contact shifts to one edge and the elements load unevenly. An oval or pinched housing creates two load zones instead of one. Local stress rises and life collapses.
How fast it progresses: Life is cut well below the calculated figure, and the damage can be mistaken for ordinary fatigue.
Causes of misalignment & distorted seats (edge loading)
Design & seats
- Housing bores out of line; shoulders not square; weak support; soft foot; shaft deflection
Mounting, handling & storage
- Misaligned housings; pinching by cap bolts or short shims
Operating conditions
- Thermal growth or deflection under load
How to confirm it is misalignment & distorted seats (edge loading)
- Read the path pattern (see Read the path): off-centre band, a diagonal sweep or two zones 180° apart
- Check alignment, squareness and seat roundness
- Check shim coverage and housing flatness
How to fix and prevent misalignment & distorted seats (edge loading)
- Correct alignment, squareness and flatness before fitting the new bearing
- Shim to cover the full base of the housing; check seats for roundness
- Use a self-aligning bearing type where deflection is inherent
Easily confused with
- Subsurface-initiated fatigue: Ordinary fatigue spalls sit in the load zone and centre of the track; edge loading hugs one side.
Worth knowing
How to read it
On the non-rotating ring the wear path is not parallel to the raceway edges. Typical sources are bent shafts, burrs or dirt on shoulders, shaft threads that are not square with the seat, and locknut faces that are not square to the thread. Use ground or single-point-turned threads and precision locknuts, and measure the runout of shoulders and seats.
Housing high spots and pinch points
A raised area in the housing seat, left by a tool when the old outer ring was driven out, transfers through the ring and loads the raceway locally. A split housing that pinches the ring does the same. Both give a spall that sits exactly opposite the mark on the outside diameter, so always check the outside of the ring.
Other related modes
Questions about misalignment & distorted seats (edge loading)
What causes misalignment & distorted seats (edge loading) in a bearing?
Housing bores out of line; shoulders not square; weak support; soft foot; shaft deflection. Misaligned housings; pinching by cap bolts or short shims. Thermal growth or deflection under load.
How do you fix or prevent misalignment & distorted seats (edge loading)?
Correct alignment, squareness and flatness before fitting the new bearing. Shim to cover the full base of the housing; check seats for roundness. Use a self-aligning bearing type where deflection is inherent.
What does misalignment & distorted seats (edge loading) look like?
Wear or spalling concentrated on one side of the raceway instead of centred. A path that sweeps from one edge of the stationary ring to the other.