A machine for automatically making rigid covers for binding: - a horizontal belt designed to individually feed cardboard frames of said covers with a respective transversal central portion and a covering layer, said transversal central portion, said covering layer and said cardboard frame being superposed in advance by interposing a layer of glue between them, whereby the covering layer protrudes the transverse edges of the cardboard frame to form first and second protruding transverse edge portions (310, 320); - a pair of juxtaposed horizontal rollers rotating about a respective axis for pressing the covering layer and the cardboard frame against each other; - a brush rotatable about a respective axis parallel to the axis of the horizontal rollers in a direction which is opposite to a direction of feed of the assembly formed by said covering layer and said cardboard frame, said brush being loacated at a height enabling the lifting and folding back of the first protruding transverse edge and then of the second protruding transverse edge portion of the covering layer onto corresponding transverse edges (210, 220)of the cardboard frame; - a first pair of juxtaposed rollers, adjacent to said brush and superposed for pushing the assembly (20, 200, 30) in the forward feed direction, both lying on a first side of the brush; and - a second pair of juxtaposed rollers, adjacent to said brush and superposed for pushing the assembly (20, 200, 30) backwardly, both lying on a second side of said brush; said machine being characterised in that it comprises feed and thrust means (80r, 81, 84, 54) interposed between said first and second pairs of juxtaposed rollers (60, 60') and designed to retain and move said assembly (20, 200, 30) made up of said covering layer and said cardboard frame between said first and second pairs of rollers (60, 60') even if the longitudinal dimensions of said assembly (20, 200, 30) are less than the longitudinal distance between said first and second pairs of juxtaposed rollers (60, 60'). - a horizontal belt designed to individually feed cardboard frames of said covers with a respective transversal central portion and a covering layer, said transversal central portion, said covering layer and said cardboard frame being superposed in advance by interposing a layer of glue between them, whereby the covering layer protrudes the transverse edges of the cardboard frame to form first and second protruding transverse edge portions (310, 320); - a pair of juxtaposed horizontal rollers rotating about a respective axis for pressing the covering layer and the cardboard frame against each other; - a brush rotatable about a respective axis parallel to the axis of the horizontal rollers in a direction which is opposite to a direction of feed of the assembly formed by said covering layer and said cardboard frame, said brush being loacated at a height enabling the lifting and folding back of the first protruding transverse edge and then of the second protruding transverse edge portion of the covering layer onto corresponding transverse edges (210, 220)of the cardboard frame; - a first pair of juxtaposed rollers, adjacent to said brush and superposed for pushing the assembly (20, 200, 30) in the forward feed direction, both lying on a first side of the brush; and - a second pair of juxtaposed rollers, adjacent to said brush and superposed for pushing the assembly (20, 200, 30) backwardly, both lying on a second side of said brush;