Design and layout of bearing assembly bearing clearance, press fit

Theoretical bearing clearance

Bushes made from KS PERMAGLIDE® P1 and P2 are pressed into the housing and fixed in place radially and axially. No further measures are required. For rigid housings and shafts, the fitting tolerances from Table 1 result in the following:
  • The press fit
  • The bearing clearance as per Table 6

The theoretical bearing clearance is calculated as follows:

[12] Δsmax = dGmax – 2 · s3min – dWmin
[13] Δsmin = dGmin – 2 · s3max – dWmax
Δsmax [mm] Maximum bearing clearance
Δsmin [mm] Minimum bearing clearance
dGmax [mm] Maximum diameter of housing bore
dGmin [mm] Minimum diameter of housing bore
dWmax [mm] Maximum shaft diameter
dWmin [mm] Minimum shaft diameter
s3max [mm] Maximum wall thickness
s3min [mm] Minimum wall thickness (see Tab. 4)


Widening the housing bore is not taken into consideration in the bearing clearance calculation.
For calculating the press-fit U, the tolerances of the housing bore are stated in Table 1 and the dimensions of the bush outside diameter DO are stated in Table 2.

Press fit and bearing clearance

The bearing clearance and press fit can be influenced by the measures shown in Tab. 7:
  • At high ambient temperatures
  • Depending on the housing material
  • Depending on the housing wall thickness.

Smaller clearance tolerances require narrower tolerances for the shaft and bore.


When using shafts with tolerance zone position h, the bearing clearance for 5≤dW<80 (P10, P14, P147) and dW<80 (P 11) must be verified using equations [12] for Δsmax and [13] for Δsmin.

Tab. 1: Recommended fitting tolerances
Tab. 2 - Dimensions for outside diameter Do
Tab. 3 - Wall thickness s3 for P1 bushes and flange bushes
Tab. 4 - Wall thickness s3 for bushes made from KS PERMAGLIDE® P20/P200
Tab. 5 - Outside bevel Co and inside bevel Ci (Fig. 2) for bushes with metric dimensions to DIN ISO 3 547-1, Table 2
Tab. 6: Theoretical bearing clearance after press-fitting bushes or flange bushes with metric dimensions, without consideration of possible widening of the bore
Tab. 7 - Errors, consequences and measures in relation to press fit and bearing clearance at high ambient temperatures, with special housing materials or housing wall thicknesses
* On request
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