What can be accomplished with just a torch and compressed air? We can think of many things, but bringing a 17-foot-long marine shaft into ±.002 in tolerance was not on our list.
Heat straightening (PDF) utilizes an oxy-acetylene flame that is used to quickly heat a small section of a workpiece. As the metal cools, it contracts more than it expanded when heated, resulting in a changed volume. With skill, any distortions on a shaft can theoretically be straightened out with enough time (and oxy-acetylene). Heat straightening is commonly applied to steel but works on nickel, copper, brass and aluminum additionally.
[Keith Fenner’s] standard process for trueing stock is sensitive enough that even sunlight can introduce irregularities, but at the same time is robust enough to carry out in your driveway. However, even though the only specialty tools you need are a torch, compressed air and work supports, watching [Keith] work makes it clear that heat straightening is as much an art as it is a science. Check out his artistry in the video below the break.
[Keith] is not new here. We’re big fans of [Keith’s] YouTube channel; he works on everything from harpoons to sailboats and has more experience than you could shake a stick at. In addition to the big ticket item, we enjoyed watching [Keith] remove a thoroughly stuck 3 in nut with only a hammer. Not working on 17 ft marine shafts? This DIY surface grinder might be something you can roll with.