iglidur® - Tolerances
Picture 13: Measuring of the inner diameter of a press-fitted bearing
The installation dimensions and tolerances of the iglidur® bearing are dependent on material and wall thickness. The humidity absorption and thermal expansion are crucial for the material. Bearings with low humidity absorption can be built in with small bearing clearance. For the wall thickness: Thicker the bearings, greater must be the bearing clearance.
Thus arise different tolerance classes for iglidur® bearings. With these tolerances iglidur® bearings can be operated according to the installation recommendations above the respective permissible range of temperatures and in humidity in the room up to 70%. If there is higher humidity or the bearings are operated under water, materials with low moisture absorption should be preferred.
iglidur® bearings are press-fit bearings for bores with the H7 standard bore. On the one hand, this press-fitting fastens the bearings to the housing and on the other, the inner diameter of the bearings is only formed by that.
The inspection of the bearing, installed in a bore with minimum size, takes place both with a dial gage and a plug gage.
Press-fitted in the bore, the go-side of the gage must smoothly pass the bearing.
At the measuring levels (compare Pic. 13), the inner diameter of the bearings must lie along with the dia tester within the specified tolerance.
Figure 13: The position of the measuring levels (1, 2, 3 = measuring lines)
Despite careful manufacturing and installation of the bearing, variations and troubles connected with installation dimensions and tolerances can arise. Bore is not properly chamfered - the bearing scrapes off on the outside. A centering pin is used to enlarge the bearings' inside when it is pressed in. The bore does not correspond to the H7 tolerance. The housing is made of a soft material that gets enlarged by the bearing when pressed in. The shaft is not H-tolerant. The measuring doesn't take place within the measuring lines.
Due to this reason, we have listed the most frequent causes for variations. In many cases the causes for variations can be quickly found with this troubleshooter.
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