Tools for expanding downhole tubulars into each other or in open hole are disclosed. One embodiment uses a movable cone biased by Bellville washers to move longitudinally against such bias and allow collets to move radially in or out to a predetermined maximum diameter. A release system allows collet retraction to avoid hang up on removal. In an alternate embodiment, more suitable for open hole applications, pressurized gas pushes a movable cone longitudinally against the collets. A stationary cone is on the opposite side of the collets from the movable cone. The collet rides out or in between the cones and raises the gas pressure when forced in. A pressure actuated release allows the lower cone to shift downwardly to allow the collets to retract for removal.