A guy came into my LBS and showed off a tool that he made to remove dents from bike tubes. First off it only works for seat and head tubes because you have access to the inside. He is a machinest by profession and basically he designed a tool that works like the old stem inside of the steer tube. It basically uses two metal cylinders that have an angled ramp on one end of each. One cylinder is fixed while the other floats on a threaded rod. The rod goes through the fixed cylinder that is unthreaded. As you tighten the threaded rod it forces the two cylinders to engage eachother and the two angled ends act like ramps forcing them to expand against one another. This causes them to press against the dent and push it out. I have seen it done on a chrome seat tube of an Atala track bike and it worked like a charm.
Ray Homiski
Elizabeth, NJ