Tapered roller bearings are commonly found in wheel bearings, transmission, differentials, and other automotive systems. They consist of two parts, the bearing cone with the roller bearing, and a “race”, which is the highly polished and hardened surface on which the bearing rides. The race is pressed into the part or casting and the roller bearing installed on top of it.
So let’s say you have a bearing race (transmission, wheel, differential or other) in a “blind” hole that you need to replace. By “blind” we mean you can’t access it from the back of the race, or there is no “lip” to catch to the drive out the race with the traditional brass drift and hammer. Or the race is “stuck” and you risk damaging the part itself by attempting to hammer it out, the races being a hardened material, like these Mercedes wheel bearing races in the photo below. Some shops don’t bother changing these because they are very difficult to drive out of the wheel hub without damage. This is not a good thing because the new bearings will wear out prematurely if they are installed on worn or damages races.
Put away that hammer, and break out the MIG welder. You carefully MIG weld a circular bead on the race surface itself. As the weld cools, the bearing race shrinks because of the weld contracting the metal, and the race falls out of the part. No damage to the part from punch or chisel. It’s like magic of thermodynamics, with some help with the Atlantic Motorcar Center. 😉