Clear out a workspace outside on concrete. This space should be about 10-feet square. Move any combustible materials or containers out of the way as you work.
Determine the areas to repair. In most cases, the rim will become bent or misshaped over time and heavy use. Put on your protective eyewear and glasses before moving onto the next steps.
Turn on the blow torch and ignite. You will want to be close to the rim so you won't have to travel around the workspace. Hold the rim on the opposite side of the area that will be repaired.
Apply the torch flame to the damaged area of the rim. Heat the area for a few minutes. Hold the flame only in the damaged area. The rim will become pliable as it heats up.
Turn off the torch and quickly but carefully place the hot section of the rim on the concrete. Hit the hot area with a hammer, reshaping the rim to its original round shape.