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Measuring Clearance Reduction

Measuring Clearance Reduction

The method using feeler gauges for measuring the radial internal clearance before and after mounting bearings is applicable for medium and large-sized bearings. Before measuring, rotate the inner or outer ring a few times. Make sure that both bearing rings and the roller complement are centrically arranged with respect to each other.

For the first measurement, a blade should be selected, that is slightly thinner than the minimum value for the clearance. During the measurement, the blade should be moved back and forth until it can be inserted to the middle of the roller. The procedure should be repeated, using slightly thicker blades each time, until a certain resistance is felt when moving between

  • outer ring and uppermost roller - before mounting
  • Measuring the radial clearance prior to mounting

  • outer ring and lowest roller - after mounting.
  • Measuring the radial clearance with bearing on the shaft

    For large bearings, especially those having a rather thin-walled outer ring, the measurements may be affected by the elastic deformation of the rings, caused by the weight of the bearing or the force to draw the feeler gauge blade through the gap between the raceway and an unloaded roller. To establish in such cases the “true” clearance before and after mounting, the following procedure should be followed (fig 1):

    Measure the clearance "c" at the 12 o'clock position for a standing bearing or at the 6 o'clock position for a bearing hanging on a journal.

    Measure clearance "a" at the 9 o’clock position and "b" at the 3 o'clock position without the bearing being moved.

    Obtain the "true" radial internal clearance with relatively good accuracy from 0,5(a+b+c).

    Fig 1. Measuring the radial clearance for large bearings

    Recommended values for reduction of radial internal clearance are provided in table.

    Detailed instructions for a selected bearing can be found at skf.com/mount.