Both practice and theory state that the principal factors which influence the stability of gear transmission are base circle pitch deviation and tooth form error, the former can cause the abrupt change of gear ratio when from one tooth to another, the latter can cause the change of instantaneous gear ratio.

This paper presents the tolerance range displacement method, with which the basic deviation of a hole is determined and therefore the basic hole system becomes the basic shaft system.

Basic the analyst of parts reality survey size in machine survey and drawing,the article has started the way that how to decided the coordinate size,tolerance and concert,basic deviation and deviation.

Considering the randomicity of base pitch error,which is one of the main manufa.

From effects of base pitch error on radius of action, the formulas of the driven gear transient angular velocity and the impact energy are developed,which are helpful not only to analyse and calculate influence of base pitch error on the stationary and noise of mesh,but also to show clearly the changing process of driven gear angular velocity in the zone of crest action.