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To make a proper fit selection, one must consider the type of load, the operating environment (i.e., ambient temperature), the type of shaft or housing, and the type of bearing. The two tables followed give some general recommendations for the selection of fits for radial bearings.

Interference:
"Press fit" or "loose fit" are terms used to distinguish the amount of interference that exists between two mating components.
 

Proper fit selection ensures that the inner and outer rings do not slip with respect to the shaft or housing. "Creep" occurs when the interference is not sufficient for the operating conditions.
Creep causes abrasive wear, shaft vibration, and excessive temperature rise. On the other hand, an excessive interference fit will eliminate the bearing operating clearance and also lead to a temperature rise. Excessive interference fits also increase the difficulty of assembly and the risk of bearing damage during assembly. Both of the above conditions can ultimately lead to poor bearing performance.
Table 1 gives the general criteria for selection of interference with respect to the basic load conditions.

 

Load Conditions

Fits

Rotating inner ring load
Inner ring : stationary
Outer ring : rotating
Direction of load : constant

Inner ring : interference fit
Outer ring : loose fit

Stationary inner ring load
Inner ring : stationary
Outer ring : rotating
Direction of load : constant

Inner ring : loose fit
Outer ring : interference fit

Stationary inner ring load
Inner ring : rotating
Outer ring : stationary
Direction of load : rotating with outer ring

Inner ring : interference fit
Outer ring : interference fit

Rotating inner ring load
Inner ring : stationary
outer ring : rotating
Direction of load : rotating with outer ring

Inner ring : interference fit
Outer ring : loose fit

1) Interference fit is preferred for separable bearing.
Table 1


ISO Nomenclature
 
Standard metric dimension tolerances for bearing shaft diameters and housing bore diameters are governed by the lnternational Standards Organization (ISO). Fits are designated by a letter followed by a number. Letters in lower case (e.g., j6) refer to fitting onto a shaft while letters in upper case (e.g., H7) refer to fitting into a housing. Figure 1 summarizes the common shaft and housing fits. The actual shaft and housing tolerance for various fit designations depend on the respective diameter and are listed in ISO shaft and housing fit tables which are available from VISTA.
   
Fit With Shaft  
   

Bearing type

Load conditions

Ball bearings

Cylindrical and tapered ball bearings

Spherical roller bearings

Shaft fits

Shaft diameter
mm

Cylindrical
bore bearings

Rotating
inner ring
or
indeterminate
direction
load

Light or
fluctuating
variable load

- 18

-

-

h5

18 - 100

- 40

-

js6

100 - 200

40 - 140

-

k6

-

140 - 200

-

m6

Normal to
heavy load

- 18

-

-

js5

18 - 100

- 40

- 40

k5

100 - 140

40 - 100

40 - 65

m5

140 - 200

100 - 140

65 - 100

m6

200 - 280

140 - 200

100 - 140

n6

-

200 - 400

140 - 280

p6

-

-

280 - 500

r6

Very heavy or
shock load

-

50 - 140

50 - 100

n6

-

140 - 200

100 - 140

p6

-

200 -

140 -

r6

Static
inner ring
load

Inner ring axial
displacement
required

All shaft diameters

g6

Easy axial
displacement of
inner ring not
required

All shaft diameters

h6

Tapered bore
bearings
(with sleeve)

All load

All shaft diameters

h9/IT5