Why Choose Mounted Unit Bearings?

Slip Fit

Tightening the Set Screw

The most common ball bearing units contain insert bearings almost identical to the 6200 and 6300 series electric motor bearings. Upon comparison, the most obvious differences would be: 1) the modification of the bearing’s outside diameter (O.D.) — the insert bearing in NTN housed units features a curved or spherical O.D. — and, 2) an extended inner ring (I.R.).

The insert’s spherical O.D. fits into a corresponding spherical inner diameter (I.D.) of the housing and allows the insert bearing to slip within the housing and to compensate for any misalignment. The misalignment may occur for a number of reasons: either the bearing unit has been mounted improperly, or, the span of the shaft between the bearings is long and/or, heavy loads are present. The latter two could cause shaft deflection (flexing), resulting in misalignment. Without this aligning feature, the bearing raceways and balls would be subjected to higher stress levels which in turn would lead to shorter bearing life, or premature bearing failure.

The inner ring has been extended to provide the means to secure the insert bearing to the shaft. Various locking devices will be covered in greater detail later in the guide.

Limitations of Bearing Units

While ball bearing units are useful in applications requiring a simply designed, misalignment tolerant, easily mounted, versatile bearing, they do have limitations. One is that these bearings are generally sealed with heavy contact seals, therefore their speed capability is limited. In addition, they are not typically used in high precision applications because of their loose shaft fits.