Abstract: Cutter teeth and gear teeth are simplified as mechanical models, The bending deformation at contact nodes is calculated by applying the three – dimension finite element method and analyzing their mechanical condition, the relation curve between shaving force and bending deformation is drawn out. The contact deformation at transient engaging point is derived from deeply analyzing geometric property and kinematics relationship between the two action flanks by use of engagement principle, differential geometry, elastic and plastic mechanics, etc. At last, the concave error of gear profile is quantitatively described by combining bending deformation and contact deformation.

Key words: Bending deformation, Concave error, Contacting deformation