Methods for expanding a tube to create a tight fit or an interference fit with one or more fins for the manufacture of a heat exchanger are disclosed. The methods can include providing an internal pressure to the tubes in a successive pulsing manner with each pulse having a short duration. The methods can include creating a temperature differential between the bend sections of the tubes and the straight sections of the tubes such that the bend section has a lower temperature than the straight sections. The methods can include creating an external pressure differential between the bend sections of the tubes and the straight sections of the tubes such that the external pressure acting on the bend sections is greater than the external pressure acting on the straight sections.