On steam locomotives the wheel thread replacements are heat shrunk on the wheel body, diesel locomotives the fractured or worn wheel, one piece, is pressed off the axle and new wheel pressed on. A significant wheel torque force would be required to separate the wheel thread from the wheel plate, if the wheel thread had a progressive crack that grew through the wheel thread cross section radially, and was not identified by inspection the crack can break through the wheel thread replacement, the frictional fit retention force would be lost, and the wheel thread ring would come off the wheel plate. As for diesel locomotive the wheels are cast or dye forged steel and have a condemning radial wheel limit, these wheels are hydraulically pressed on and off the axles, press on tonnages are recorded per AAR Standards. Wheel inspections are conducted per FRA Requirements. If my memory is correct to press on a 36 in wheel on the wheel axle the required about 140 tons. If a wheel fractured and broke into segments a derailment most probably would occur.