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Mounting recommendations

Compared to other rolling bearings, mounting super-precision bearings requires more accuracy, more caution and more advanced skills.

Mounting bearings with thin-walled rings

Super-precision bearings often have rings that are thin relative to their size. For these bearings, only limited mounting forces should be applied. Therefore, SKF recommends using hot mounting methods for all super-precision bearings with thin-walled rings. For bearings in the NNU 49 series with a tapered bore, SKF recommends using the oil injection method.

Hot mounting

Super-precision bearings are typically mounted with a low degree of interference. That means a relatively small difference in temperature between the bearing ring and its mating components is required. The following temperature differences are often sufficient:
  • 20 to 30 °C (35 to 55 °F) between the inner ring and shaft
  • 10 to 30 °C (20 to 55 °F) between the housing bore and outer ring
To heat bearings evenly and reliably, SKF recommends using SKF electric induction heaters (fig. 1). Stepped sleeves are sometimes used to locate bearings on a shaft and are therefore installed with a tight interference fit. Because of this, stepped sleeves require a greater difference in temperature between mating components during installation. Temperature differences for installation are listed for:
  • stepped sleeves without O-rings table 1
  • stepped sleeves with O-rings table 2
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