GB 49 internal clearance gauges

SKF internal clearance gauges in the GB 49 series are designed for use with double row cylindrical roller bearings ranging from NNU 4920 BK to NNU 4960 BK. GB 49 series internal clearance gauges are able to accurately measure the internal envelope diameter of the roller set when the rollers are in contact with the outer ring raceway.
Depending on their size, GB 49 internal clearance gauges are available in two different designs (fig.1 and product table). They have a slotted gauge body, so that both gauging ring halves can be brought to bear on the roller set with the appropriate pressure, as a result of the inherent resilience of the material. The outside cylindrical surface of the gauging ring has two diametrically opposed ground gauging zones. The gauge body can be compressed by means of an adjustment screw. This enables the gauge to be positioned inside the roller set without damaging the rollers or the gauging zones.


The typical gauging procedure:
  1. Insert the GB 49 gauge in the outer ring and roller assembly and loosen the adjustment screw until the two gauging ring halves are in contact with the roller set.
  2. Set the dial indicator on the GB 49 gauge to zero.
  3. Compress GB 49 using adjustment screw and remove from outer ring assembly.
  4. Reset GB 49 so that dial indicator reads zero again using adjustment screw.
  5. Set a stirrup gauge to GB 49 gauge diameter setting the stirrup gauge dial indicator to zero.
  6. Drive the inner ring up onto its tapered seat monitoring the diameter expansion with the stirrup gauge until the dial indicator reads zero plus the desired preload or zero minus the desired clearance.
For additional information, refer to Mounting.


The accuracy of GB 49 gauges is within 1 μm for sizes ≤ 38 (GB 4920 to GB 4938) and within 2 μm for sizes ≥ 40 (GB 4940 to GB 4960).

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