The ideal mounting for a precision bearing is line to line on both shaft and housing. Such a fit has no interference or looseness. For random fitting the fit tolerances may need to be increased to meet the lot variances. For selective fitting the bearing inner and outer diameter should be accurately measured, then the shaft and housing machined to suit.
Interference fits should be used with care as they can distort the raceway and reduce radial internal clearance. In preloaded pairs, reducing the internal radial clearance increases the preload. If excessive, the results can be significantly reduced speed capability and higher operating temperatures which will ultimately reduce life.
Some applications require interference fits such as:
Radial internal clearance is reduced by approximately 80% of the interference fit.
Interference fits are usually applied to the rotating ring.
Loose fits may be suggested when:
Fits are often overlooked and is arguably the most common bearing handling mistake.
The table below is simply a guideline as there are many influencing factors to be considered such as.
Therefore the appropriate fit may fall somewhere in between.
| ROTATING RING | INNER RING | OUTER RING | ||
|---|---|---|---|---|
| APPLICATION | DESIRED FIT TYPE | FIT(inches) | USE SHAFT DIAMETER | USE HOUSING DIAMETER |
| Low speed, or spring preload. | Loose | .0001L to .0005L | d - .0003 d - .0005 | D .0001 D .0003 |
| Medium speed | Line to Line | .0002L to .0002T | d - .0000 d - .0002 | D - .0000 D - .0002 |
| High speed | Light press | .0000 to .0004T | d .0002 d - .0000 | D - .0002 D - .0004 |
| High speed, high load | Tight press | .0002T to .0006T | d - .0002 d - .0004 | D - .0004 D - .0006 |
| STATIONARY RING | INNER RING | OUTER RING | ||
|---|---|---|---|---|
| Most applications | Line to line to loose | .0000 to .0004L | d - .0002 d - .0004 | D - .0000 D .0002 |
L = Loose fit, T = Tight fit, d = Bearing I.D., D = Bearing O.D.