Abstract: A newspaper inserting machine for inserting supplements or inserts into signatures or newspaper jackets improves upon conventional inserting machines by modifying the conventional inserting machines existing belt gripping mechanisms for gripping the inserts and for propelling the inserts into the newspaper jackets as the jackets are moved by a conveyor past insert-containing containers. The existing belt gripping mechanisms are modified to be adjustably positionable to accommodate inserts of different thicknesses and are also modified to be adjustably positionable in directions parallel with the conveyor to accommodate inserts of different sizes while reducing the machine set-up time required by operators for different sizes of inserts. The adjustability of the belt gripping mechanisms also increase the capacity of conventional machines for the number of different inserts which can be placed into the newspaper jackets along a conveyor of predetermined length.