CNC, or computer numerical control, machining has in many ways revolutionized what can be made out of metal, wood or plastic. As with 3D printing, which uses many of the same principles as machines that cut material away, you simply program it and let it work.
Hobbyist CNC machinery, such as the Sherline mills equipped with this technology have been filtering down to the maker market for quite some time. Unfortunately though, many of these machines require a parallel port for operation, and from personal experience, you can’t use just any USB to parallel connector with these devices.
The good news is that there are a few options. You can find an old desktop that has a parallel port fairly cheaply, or even attempt to install a new one via an expansion card, but that seems like a lot of work, and machine control may be sluggish. Special CNC USB to parallel adapters look like a very good option, but you’ll still need to provide your own software and cost quite a bit more than a normal adapter. Finally, there are Arduino-based solutions, like this one from Tindie, however, that one doesn’t appear to offer any user interface while running.
Another alternative for control is the rt-stepper USB to parallel port dongle, along with its PyMini machine control software. The software’s minimal interface allows you to control machining runs on any modern computer, laptop, or netbook, and since it’s written in Python, you can run it on Mac, Windows or Linux. The software/dongle is demonstrated below on a Sherline milling machine, which looks pretty neat with its handles spinning automatically!