Method of fabricating a gear train (51, 51') that includes the following steps: a) taking a substrate that includes a top layer and a bottom layer made of micro-machinable material and secured to each other by an intermediate layer; b) etching at least one pattern in the top layer and the intermediate layer until the bottom layer is exposed, so as to form at least one first cavity belonging to a first wheel set (55, 55'); c) coating at least the bottom of said at least one first cavity with an electrically conductive coating; d) electroforming a material, at least in the bottom of said at least one first cavity; e) etching a second pattern in the bottom layer as far as the coating of said electrically conductive material, so as to form at least one second cavity belonging to a second wheel set (57, 57'); characterized in that the method of fabricating further includes the following steps: f) structuring a photosensitive resin (42, 43, 48) on the bottom of the bottom layer, forming a sheathing on the walls of said at least one second cavity and at least one recess that flares out coaxially from said at least second cavity; g) continuing the electroforming started in step d) so as to fill said at least one first cavity and starting to electroform a material in said at least one second cavity and said at least one recess, so as to form an arbour (53, 53') fitted with a collar (52, 52'); h) removing the photosensitive resin (38, 40, 42, 43, 48); i) removing the intermediate layer so as to separate the first (55, 55') and second (57, 57') wheel sets; and j) releasing the fabricated wheel set (51, 51') from the substrate. a) taking a substrate that includes a top layer and a bottom layer made of micro-machinable material and secured to each other by an intermediate layer; b) etching at least one pattern in the top layer and the intermediate layer until the bottom layer is exposed, so as to form at least one first cavity belonging to a first wheel set (55, 55'); c) coating at least the bottom of said at least one first cavity with an electrically conductive coating; d) electroforming a material, at least in the bottom of said at least one first cavity; e) etching a second pattern in the bottom layer as far as the coating of said electrically conductive material, so as to form at least one second cavity belonging to a second wheel set (57, 57'); characterized in that the method of fabricating further includes the following steps: f) structuring a photosensitive resin (42, 43, 48) on the bottom of the bottom layer, forming a sheathing on the walls of said at least one second cavity and at least one recess that flares out coaxially from said at least second cavity; g) continuing the electroforming started in step d) so as to fill said at least one first cavity and starting to electroform a material in said at least one second cavity and said at least one recess, so as to form an arbour (53, 53') fitted with a collar (52, 52'); h) removing the photosensitive resin (38, 40, 42, 43, 48); i) removing the intermediate layer so as to separate the first (55, 55') and second (57, 57') wheel sets; and j) releasing the fabricated wheel set (51, 51') from the substrate.