In this paper, a combination of loaded tests, coordinate measurements, surface reverse engineering and a special finite
element method is employed to study the effect of break-in wear on meshing contact between the mating surfaces of
worm gearing parts. Three different wheel tooth geometries are investigated in this paper: the as-cut geometry cut by a
fully oversized hob, the conjugate tooth geometry generated by the mating worm thread and the broken-in wheel tooth
surface. The broken-in wheel tooth is measured with a coordinate measurement machine and reverse engineered. The
contact stresses between the worm thread and these three different wheel tooth geometries are studied with the CAPP
Software (Contact Analysis Program Package [13]). Based on the obtained contact pressure values, the effects of wear on
contact stresses are investigated. It is found that the three maximum contact pressures differ significantly. The contact
patterns, the load sharing and the transmission errors are also discussed.