Cracks, chips, brinelling, nicks, scratches and scuffing
Six kinds of damage that usually come from loads, impacts or handling, with the fix for each.
Cracks and chips
Cracks include slight cracks, splitting and fracture. Chips are a type of failure at a rib of a ring or at a corner of a roller.
Cracks and chips: causes and fixes
| Type | Causes | Countermeasures |
|---|---|---|
| Cracks | Heavy load; too much internal load from poor mounting; too much interference or shaft or housing out of shape; sudden sliding that heats the bearing; heat from a shortage of lubricant | Find and reduce the heavy load; remove thermal shocks; reduce interference |
| Chips | Heavy axial load or impact; hitting with a hammer or tool during mounting or removal | Improve mounting and removal methods and handling; check for excessive load |
Brinelling and nicks
Brinelling is a dent in a raceway at the contact with a rolling element, caused by plastic deformation. It can also be small dents made by hard particles. Nicks are damage from a direct blow, for instance from a hammer or a tool.
Brinelling and nicks: causes and fixes
| Type | Causes | Countermeasures |
|---|---|---|
| Brinelling | Extremely heavy static or impact load; solid foreign matter caught between parts | Find the heavy load or impact; improve sealing; wash the shaft and housing carefully; filter the oil; check whether the same bearing also shows flaking |
| Nicks | Poor mounting or removal; careless handling | Improve mounting, removal and handling |
Scratches and scuffing
A scratch is a fairly shallow flaw from sliding contact. Scuffing is a flaw from high contact pressure and heat on the rolling surface, and serious scratches are generally called scuffing. In separable bearings, axial scratches often come from the edge of a roller touching the raceway while the bearing is fitted. Scuffing on roller end faces and rib faces leaves flaws that look like cycloid curves.
Scratches and scuffing: causes and fixes
| Where | Causes | Countermeasures |
|---|---|---|
| Made while mounting | Careless fitting or removal | Improve the method; centre accurately |
| Roller end and rib faces | Poor lubrication at the contact; too much preload; foreign matter; abnormal axial load | Review lubricant and method; check for abnormal load; improve sealing |
| Raceway and rolling surfaces | Rolling elements not turning properly; poor lubrication; foreign matter | Review lubrication; improve sealing; clean the shaft and housing thoroughly |