A tool for assembling a seal device of a gas turbine engine, the tool comprising: a first tool die including a first die base, a first die curb and a first die bumper, the first die curb projecting axially out from the first die base along an axis, the first die curb extending circumferentially about the axis, the first die bumper spaced radially outward from the first die curb by a first die channel, the first die bumper projecting axially out from the first die base along the axis, and the first die bumper extending circumferentially about the axis; a second tool die including a second die base, a second die curb and a second die bumper, the second die curb projecting axially out from the second die base along the axis, the second die curb extending circumferentially about the axis, the second die bumper spaced radially outward from the second die curb by a second die channel, the second die bumper projecting axially out from the second die base along the axis, and the second die bumper extending circumferentially about the axis; a centering element extending axially along and circumferentially about the axis; a receptacle configured to receive a seal device, the receptacle extending axially along the axis within the tool between the first tool die and the second tool die, and the receptacle projecting radially inward into the tool to the centering element; and an actuator configured to axially press the seal device between the first tool die and the second tool die; wherein the centering element comprises an outer cylindrical surface configured to radially contact a carbon seal element of the seal device within the receptacle. a first tool die including a first die base, a first die curb and a first die bumper, the first die curb projecting axially out from the first die base along an axis, the first die curb extending circumferentially about the axis, the first die bumper spaced radially outward from the first die curb by a first die channel, the first die bumper projecting axially out from the first die base along the axis, and the first die bumper extending circumferentially about the axis; a second tool die including a second die base, a second die curb and a second die bumper, the second die curb projecting axially out from the second die base along the axis, the second die curb extending circumferentially about the axis, the second die bumper spaced radially outward from the second die curb by a second die channel, the second die bumper projecting axially out from the second die base along the axis, and the second die bumper extending circumferentially about the axis; a centering element extending axially along and circumferentially about the axis; a receptacle configured to receive a seal device, the receptacle extending axially along the axis within the tool between the first tool die and the second tool die, and the receptacle projecting radially inward into the tool to the centering element; and an actuator configured to axially press the seal device between the first tool die and the second tool die; wherein the centering element comprises an outer cylindrical surface configured to radially contact a carbon seal element of the seal device within the receptacle.