An alternative equation of meshing for worm-gear drives is proposed. This e
quation has advantage over the commonly used equation of meshing when it is
used to study the undercutting phenomenon, to perform revel-se engineering
and to find the meshing area of worm-gear drives. From the new alternative
equation, the equations of the boundaries of the three-dimensional meshing
area and the limiting line on the worm surface that distinguishes the non-
undercut area and the undercut area are derived. [S1050-0472(00)01302-7].