a machine for inserting plastic pre - formed helical coils into aligned holes at an edge of respective collated books for binding the books is adjustable to accommodate different thickness books and respective different diameter and pitch of coil . the machine has a platen having an edge comb at which the edge of the book is presented and a coil drive for rotating the helical coil parallel to the edge of the platen . two spine formers support the book such that its spine takes up a curved shape in side elevation and a clamp with an edge comb clamps the book on to the platen . both the edge comb of the platen and of the clamp are provided as insert portions attachable to the respective element for easy replacement of the pitch . the location of the coil drive is automatically adjusted by measuring the coil diameter with a gauge . the clamp moves along an arc which automatically adjusts the clamping location for thickness of the book .