My goodness, IR can only penetrate a few microns into the steel gears we heat shrink onto shafts, but the sure do heat up fast from the torch whose heat is only penetrating a few microns deep.
Simple physics test olfraud. In which direction does heat travel. Up? Or down? Here's a hint...
--- that's just magic or so they said when they first saw one of these. But you can also conduct heat in circles. I've seen that on old stovetops and broilers.. Maybe there's some magic in that also..