Sean Ragan has put his old soldering iron to good use:

The upgrade left me with a surplus soldering iron and the opportunity to try a modification which first occurred to me when I was 10 or 11 and still playing around with Dad’s tools in our old garage, which was to try to adapt a soldering pencil barrel to accept the threads of an X-acto Type A blade holder. The idea was to be able to conveniently adapt my trusty hobby knife for hot-blade work, useful for instance in the cutting of plastics.