Much is being reported about the form and shape of running gears, little, however, about the same featuresof splines and
serration, although the latter, too, are installed in every automobile. It is, of c0urse.a well- known fact that the permissible
geometrical tolerances for spline and serration gauges are often as narrow as those for running gears. According to IS0
17025 (draft), measuring and test equipment – among which spline and serration gauges are counted – must have been
linked up with recognized national or international primary standards through an unbroken traceability chain. Since the
sixties, national standards and standard measuring devices have. therefore been available in Germany for running gears,
for example for the elements: profile, helix, pitch, tooth thickness, radial run-out of gearing, roughness. On the other
hand no direct iink-up with the SI unit mefre has so far been made at PTB for splines and serration. nor has a laboratory
been accredited within the framework of DKD. In contrast to this, several laboratories have been accredited in the United
Kingdom, one of which may calibrate up to 70 measurands that have been embodied on spline and serration gauges. If
one would proceed according to the DKD traceability criteria valid within the DKD for other geometrical measurands, a
large number of PTB calibrations on reference standards or comparison measurements with the PTB on spline and
serration gauges would be necessary. and this would, of course, involve relatively high cost. It might. therefore. be an
alternative to ensure traceability for the measuring instrument only (e.g. a CMM) – here referred to ascategory A – and to
estimate the uncertainty budget for the individual measurands. However, the smallest possible uncertainty of
measurement according to IS0 15530-4 (draft) would not be achievable in this way.