Are you using the standard little red disks, the fiberglass reinforced, or the metal? I think they're all called "reinforced". It does take some practice to not waste disks, the first time I tried ...

A bench-mounted shrinking machine is a great tool for many metalworking tasks, and they are reasonably priced. Read how this tool can be used to "tighten up" a defect on the edge of a hood. I have a ...