SummaryIf you take apart a Harbot Freight Tools 4.8V screwdriver (http://www.harborfreight.com/48-volt-cordless-screwdriver-kit-68394.html), you'll find that it has a pretty decent 2-stage planetary gear drive. Unfortunately, the housing for the gearbox normally requires the screwdriver enclosure to hold the gearbox together. I wanted to experiment with the gearbox, so I made a replacement housing holder. This is still work in progress. It's provided as a starting point for anyone else that is interested in hacking their Harbor Freight 4.8V Screwdriver. In the current iteration,the two ribs going toward the back shell (closer to the motor) are a bit too thin and possibly about 0.1mm too short. In the close up picture, you can see the rib has delaminated a bit. Still, it works to hold the gear housing together. The AD_PRT files are the Aliibre Design (now called Geomagic Design) source files. UPDATE Rev 2: Made the ribs much thicker, and added filets to reduce cracking. InstructionsYMMV, but I printed the Rev 2 with .35 mm layers, 3 extra shells, and 50% infill, with ABS. It seems to hold up very well. When you print this, break off the support for the overhanging blocks for the rear (closer to the motor) screws. Be sure to clean off any leftover sprues, swarfs, strings -- it's a bit of a tight fit.