Checking for Datum Pin Wear
The datum pins are made from Tungsten Carbide and should last between yearly services if the gauge is used properly. The datum pins are, however, a wear part, and so routine maintenance should include checking for excessive wear.
The probe measures from the lowest point of the datum pin (the reference point). If the datum pin is worn, the probe will ‘zero’ in the indentation. The Can will then sit between the worn datum face and the probe tip, bridging the wear and providing a reading higher than expected.
1. Pass a clean rag between Datum Pin and Probe Tip.
2. Put the gauge in ‘Single Point Mode’.
3. Zero the gauge.
4. Place a certified slip between the datum pin and the probe tip and take a reading (Do not hold the slip and ensure that the slip is not resting on any part of the gauge).
5. Place a second certified slip behind the first slip and take another reading
6. Calculate the difference between the two readings.
7. If this value is equal to that of the second slip (221.0um minus 101.0um equals 120um) the datum pin is worn and needs replacing.