Page 48 - NSK_CAT_E1102m_A7-141

11. DESIGN OF SHAFTS AND HOUSINGS

11.1 Accuracy and Surface Finish of Shafts 11.2 Shoulder and Fillet Dimensions Table 11. 2 Recommended Minimum Shoulder Heights for
and Housings Use with Metric Series Radial Bearings
The shoulders of the shaft or housing in contact with
If the accuracy of a shaft or housing does not meet the the face of a bearing must be perpendicular to the Units : mm
specification, the performance of the bearings will be shaft center line. (Refer to Table 11.1) The front face
affected and they will not provide their full capability. side shoulder bore of the housing for a tapered roller Nominal Shaft or Housing
For example, inaccuracy in the squareness of the shaft bearing should be parallel with the bearing axis in Chamfer
shoulder may cause misalignment of the bearing inner order to avoid interference with the cage. Dimensions Fillet Minimun Shoulder Heights hr ra hr rg
and outer rings, which may reduce the bearing fatigue The fillets of the shaft and housing should not come in Radius h (min.)
life by adding an edge load in addition to the normal contact with the bearing chamfer; therefore, the fillet (min.) r (min.) r
load. Cage fracture and seizure sometimes occur for Deep Groove Ball Angular Contact t
this same reason. Housings should be rigid in order radius ra must be smaller than the minimum bearing Bearings, Ball Bearings, (min.) (min.)
to provide firm bearing support. High rigidity housings chamfer dimension r or r1 . r (min.) Self-Aligning Ball Tapered Roller
are advantageous also from he standpoint of noise, ra (max.) Bearings, Bearings, Spherical (a) b
load distribution, etc. or Cylindrical Roller Roller Bearings (b)
For normal operating conditions, a turned finish or Bearings,
smooth bored finish is sufficient for the fitting surface; r1 (min.) Solid Needle Roller
however, a ground finish is necessary for applications Bearings
where vibration and noise must be low or where heavy Housing Fig. 11. 2 Chamfer Dimensions, Fillet Radius, and
loads are applied. r(min.) or r1(min.) 0.05 0.05 0.2 — Fig.11. 2 Shoulder Height
In cases where two or more bearings are mounted in r(min.) or r1(min.) 0.08 0.08 0.3 —
one single-piece housing, the fitting surfaces of the 0.1 0.1 0.4 —
housing bore should be designed so both bearing seats
may be finished together with one operation such as in ra h 0.15 0.15 0.6 —
-line boring. In the case of split housings, care must 0.2 0.2 0.8 —
be taken in the fabrication of the housing so the outer Bearing h 0.3 0.3 1 1.25
ring will not become deformed during installation. The r(min.)
accuracy and surface finish of shafts and housings are ra or r1(min.) 0.6 0.6 2 2.5 Table 11. 3 Shaft Undercut
listed in Table 11.1 for normal operating conditions. r(min.) 11 2.5 3 Units : mm
or r1(min.) 1.1 1 3.25 3.5

1.5 1.5 4 4.5 Chamfer Dimensions Undercut Dimensions
22 4.5 5 of Inner and
2.1 2 5.5 6 Outer Rings t rg b

2.5 2 — 6 r (min.) or r1(min.)
3 2.5 6.5 7
Shaft 43 8 9 1 0.2 1.3 2

54 10 11 1.1 0.3 1.5 2.4
65 13 14
Table 11. 1 Accuracy and Roughness of Shaft and 7.5 6 16 18 1.5 0.4 2 3.2
Housing
2 0.5 2.5 4
Item Class of Shaft Housing Bore Fig. 11.1 Chamfer Dimensions, Fillet Radius of 9.5 8 20 22 2.1 0.5 2.5 4
Bearings 12 10 24 27 2.5 0.5 2.5 4
Fig.11.1 Shaft and Housing, and Shoulder Height 15 12 29 32
Normal, Class 6 I T3 to I T4 I T4 to I T5 19 15 38 42 3 0.5 3 4.7
Class 5, Class 4 2 2 2 2 The shoulder heights for both shafts and housings for
Tolerance for radial bearings should be sufficient to provide good 4 0.5 4 5.9
Out-of-roundness support over the face of the bearings, but enough
I T2 I T3 I T2 I T3 face should extend beyond the shoulder to permit Remarks 1. When heavy axial loads are applied, the shoulder 5 0.6 5 7.4
2 2 2 2 use of special dismounting tools. The recommended height must be sufficiently higher than the
to to minimum shoulder heights for metric series radial Remarks values listed. 6 0.6 6 8.6
bearings are listed in Table 11.2 Remarks
I T3 I T4 I T4 I T5 Nominal dimensions associated with bearing mounting 2. The fillet radius of the corner is also applicable 7.5 0.6 7 10
2 2 2 2 are listed in the bearing tables including the proper to thrust bearings.
Normal, Class 6 to to shoulder diameters. Sufficient shoulder height is
particularly important for supporting the side ribs of 3. The shoulder diameter is listed instead of
Tolerance for I T2 I T3 I T2 I T3 tapered roller bearings and cylindrical roller bearings shoulder height in the bearing tables.
Cylindricality 2 2 2 2 subjected to high axial loads.

Class 5, Class 4 to to The values of h and ra in Table 11.2 should be adopted

Tolerance for Normal, Class 6 I T3 I T3 to I T4 in those cases where the fillet radius of the shaft or
I T3 I T3 housing is as shown in Fig. 11.2 (a), while the values
Shoulder Runout Class 5, Class 4 in Table 11.3 are generally used with an undercut fillet
radius produced when grinding the shaft as shown in
Roughness of Small Bearings 0.8 1.6 Fig. 11.2 (b).
Large Bearings 1.6 3.2
Fitting Surfaces
Ra

Remarks This table is for general recommendation using A 101
radius measuring method, the basic tolerance (I T)
class should be selected in accordance with the
bearing precision class. Regarding the figures of IT,
please refer to the Appendix Table 11 (page C22).

Remarks In cases that the outer ring is mounted in the
housing bore with interference or that a thin cross-
section bearing is mounted on a shaft and housing,
the accuracy of the shaft and housing should
be higher since this affects the bearing raceway
directly.

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