Excessive endplay and loose setting (scalloping)

Too much play lets the rollers fall out of step with the load. Urgency

Not separate ISO modes, but the overheating, seizure, cage and alignment problems that surround them.

What excessive endplay and loose setting (scalloping) looks like

• Scalloped dents or wear in the raceway of the stationary ring, concentrated in a small zone
• Cage pockets worn heavily, especially at the small end
• Noise and visible shaft movement before the bearing is stripped

Rotec AI schematic illustration. It shows the typical pattern and is not a photograph of a real bearing.

How excessive endplay and loose setting (scalloping) develops

In a bearing that is meant to be set with a little preload or a small controlled play, too much endplay shrinks the load zone to just a few rollers. The rollers outside it are loose, they unseat, skid and skew, and then enter the load zone suddenly and take a hard knock. That knocks scallops into the raceway and wears the cage pockets.

How fast it progresses: Wear raises the play further, so the damage speeds up. Rollers that skew can lock and tear the cage.

Causes of excessive endplay and loose setting (scalloping)

Mounting, handling & storage

• Bearing set with too much play, or a locknut or shim pack that moved
• Lock washer or end cover not clamping properly

Lubrication

• Abrasive wear that has grown the clearance over time

Bearing selection

• Wrong clearance class for the fits and temperatures

How to confirm it is excessive endplay and loose setting (scalloping)

• Measure the shaft endplay and compare it with the specified setting
• Look for scallops in a short zone on the stationary ring, with cage pocket wear at the small end
• Check the history: was the setting verified at commissioning and after a rebuild?

How to fix and prevent excessive endplay and loose setting (scalloping)

• Set endplay or preload to specification with a dial gauge, and recheck it after the first run
• Lock the setting properly (locknut with tab washer, matched shims)
• If wear has raised the play, find the cause (abrasive contamination, lubrication) before you rebuild

Easily confused with

• Abrasive wear: Abrasive wear grows clearance too, but the surfaces are dull and scratched all round.
• Adhesive wear (smearing & skidding): Smearing shows torn metal rather than regular scallops.

Catching excessive endplay and loose setting (scalloping) early

Loose bearings usually show a rise in overall vibration with harmonics of shaft speed and a raised noise floor. Check with a setting measurement, not by ear.

Other related modes

Questions about excessive endplay and loose setting (scalloping)