The details of a recent theoretical formulation of electron impact detachment of weakly bound negative ions are presented. The formalism is applied at low energies to find the behavior of the cross section near threshold. Also, the applicability of a recently proposed scaling law is discussed. The formulation uses different coordinate systems for the initial and final states. The initial state is a simple product of wave functions of each electron while the final state is a simple product of wave functions in center of mass coordinates.