The objective of this research is to develop a center-less gear lapping machine which can simultaneously make all tooth flanks of a steel gear smooth as a maximum peak-valley height (Rz) of less than 1μm in a short time without fixing it on any shaft. A work gear is meshing with two lap gears as crossed helical gears and supported by a guide gear during the lapping. The two lap gears and the guide gear are nylon gears. Lapping slurry containing abrasive grains is supplied to the meshing teeth. This paper shows the mechanism of the center-less lapping process and the structure of the lapping machine designed and manufactured by the authors. The behavior of the work gear and the removal amount are investigated during the process. Moreover, the work gears lapped using the new machine are evaluated with regard to the tooth roughness and the accuracy of the tooth profile. The life of nylon lap gears is also evaluated.
