The invention relates to a pulse generator (18) in an impulse generator (2) for a cutting tool (12), which pulse generator (18) is intended to transfer energy from a propulsion device (14) to impulses in the tool (12), where the pulse generator (18) comprises a rotatable cylinder drum (28) comprising at least one piston cylinder (30, 86, 88, 90, 92, 94, 96, 98), in which piston cylinder (30, 86, 88, 90, 92, 94, 96, 98) is arranged at least one piston (32, 87, 89, 91, 93, 95, 97, 99), which piston (32, 87, 89, 91, 93, 95, 97, 99) is arranged to compress fluid (29) during rotation of the cylinder drum (28), and that the cylinder drum (28) is arranged to discharge the fluid (29) to the propulsion chamber (6) in the discharge position of the piston (32, 87, 89, 91, 93, 95, 97, 99) via at least one opening (31, 72, 74, 76, 78, 80, 82, 84) opening into the piston cylinder in order to produce an impulse in the tool (12). The invention also relates to an impulse machine comprising an impulse generator (2).