Page 306 - needle bearings

Linear ball bearings, stroke type
NTN

Linear Ball Bearings, Stroke Type

The bearing cage with multiple ball rows (several balls
per row) configured circumferentially therein can move Shaft and housing requirements
within the outer ring in both circumferential and axial Table 3 specifies the requirements for shaft and
directions. Thus, this bearing type can rotate and housing which of the outer surfaces are used as the direct
reciprocate (but at a limited stroke) on a shaft. raceway.

Table 3 Shaft and housing requirements
Bearing construction
Maximum available length of the reciprocal stroke is Characteristics Shaft Housing
two times as long as the stroke at which the cage can Roundness (max) IT2 IT4
reciprocate within the outer ring. The outer ring is Cylindricality (max) IT2 IT4
provided at its both ends with a snap ring acting as a Surface roughness (max) 0.2a 1.6a
stopper and a wave spring is provided between the snap
ring and the cage to damp a shock acting on the cage as Surface hardness HRC58ʙ64 ʵ
well as to prevent wear of the cage. Hardened layer depth (min) 0.4mm ʵ
In addition to the standard type, a special type with
synthetic rubber seal (Tail code: LL) on the both ends of
its outer ring is also available.
How to mount
Dimensional accuracy of Bearing This bearing type can't be fixed perfectly to a housing
with interference only and, therefore, it is fixed in axial
Table 1 the bearing tolerance.
direction using a snap ring. (Refer to Fig. 1)
Table 1 Dimensional accuracy

Characteristics Dimensional tolerance
Ball inscribed circle diameter (Fw) F6
Outer ring outer diameter (D) h5

Bearing fit and radial clearance
Any linear ball bearings must be used with radial
clearance as less as possible. Particularly where linear
ball bearing is applied to a vertical shaft or high accuracy
is required, it is desirable to select and combine
appropriate bearing and shaft for securing radial
clearance in the range of 0 to -10Жm (by preloading).
Table 2 shows the bearing fits on shaft and in housing.

Table 2 Bearing fits
Operating conditions Shaft Housing
Usual operating conditions k5 (m5) H6 (H7)
1
Vertical shaft and high accuracy applications n5 (p5) J6 (J7)
1 Selective fit

Fig. 1 Axial fixing of bearing

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