When I measure the plain bearings, I find them to be considerably larger than indicated in the catalogue. Why is this?

Lars Butenschön | 2. July 2019

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Our plain bearings are press-fit bearings for housings with a standard H7 hole. This press-fitting of the bearings fixes the bearings in place in the housing, and the final inner diameter of the plain bearings is not arrived at until the bearing has been press-fitted.
The bearing size is checked when the bearing has been mounted in a hole with the minimum specified dimensions. If the bearings are measured before they are press-fitted, the outer diameter and the inner diameter are greater than when the bearings have been mounted, the difference being the so-called interference.
In spite of careful manufacturing and installation of the bearings, there can be deviations from the catalogue and questions regarding the recommended installation dimensions and tolerances. Possible reasons for this are as follows:

  • The hole has not been not chamfered correctly and bearing material is therefore scraped off during press-fitting.
  • A centring pin has been used, which has caused the inner diameter of the bearing to increase during the press-fitting process.
  • The hole does not have H7 tolerance.
  • The housing is made of a soft material that the bearing has expanded during the press-fitting process.
  • The shaft does not have h tolerance.
  • Measuring is not carried out within the measuring lines.
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