Large gears have become an indispensable part of modern technical applications. The expanding
industrial sectors of power generation and transmission, like shipbuilding industry, wind turbine
generators and petroleum conveying systems, have led to an increasing demand for large-scale gear
boxes. Thus, the qualified measurement of large gears has become more and more important as well.
Their conformance with specifications according to ISO 1 4253-1 [1 ] has to be proved, which is not
possible without a qualified statement of the task-specific measurement uncertainty. As a consequence,
the manufacturing processes cannot be controlled quantitatively and at a reasonable process capability
level, especially if tolerances are small compared to the achievable measurement uncertainty. This
specifically applies to large gears.
In recent years, large gear metrology has gained in importance among the research activities at PTB. In
this report, three current projects are presented. First of all the first national comparison for large involute
gears is described. It has been organized by PTB and is just about to be finished. The measurement
results are included in this paper. As a second step towards traceable measurements of large gears, a
special calibration laboratory is intended to be established. This is part of a joint research project, in which
a new measurement artifact of 2 m in diameter has been developed. Lastly, information about a Joint
Research Project within the European Metrology Research Programme which will start in September
201 4 is provided.