What must be observed when mounting iglidur plain bearings?

Measuring of the inner diameter of a press-fitted bearing

Fig. 1: positions of the measurement lines (1, 2, 3 = measurement lines)

Tolerances and measurement system

The installation dimensions and tolerances of iglidur® plain bearings are a function of the material and wall thicknesses. For each material, the moisture absorption and the thermal expansion are decisive factors. Plain bearings with low moisture absorption can be designed with a minimal bearing clearance. The rule of thumb for wall thickness: the thicker the wall of the bearings, the larger the clearances must be.
 
Therefore, different tolerance classes exist for iglidur® plain bearings. Within these tolerances, iglidur® plain bearings can operate in the permissible temperature range and in humidity conditions up to 70% according to the installation recommendations. Should higher air moisture levels be present, or the bearing be used underwater, materials with low moisture absorption are to be preferred.
 
With the free igus Fit calculator, you can quickly and easily calculate adaptations and tolerances according to ISO 286. In addition, the maximum and minimum dimensions as well as the associated type of fit are shown.
Go to Fit calculator
 

Check that the bearing is seated correctly

iglidur 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 test is performed when the bearing is installed in the hole with the minimum specified dimension; both using a dial gauge and a plug gauge.

• The "Go-Side" of the plug gauge, pressed into the hole, must pass easily through the bearing
• With the 3 point probe, the inner diameter of the bearing must lie within the prescribed tolerance on the measurement plane (diagram 1)

Causes for dimensional deviations

In spite of careful manufacturing and assembly of the bearings, differences and questions regarding the recommended installation dimensions and tolerances can result. For this reason, we have compiled a list of the most frequent reasons for differences. In many cases, with this troubleshooter, the reasons for the differences can be found quickly:

• The hole is not chamfered correctly, so the bearing material is removed upon press-fitting
• A centring pin was used which expanded the inside diameter of the bearing during press-fit
• The hole does not meet the recommended housing hole specifications (usually H7)
• The housing is made out of a soft material that was expanded by the bearing installation 
• The shaft is not within recommended tolerances
• The measuring is not performed within the measuring lines