Update 2023 Mar 22: Taking this down. Too many reports of it breaking and that's just disappointing. I suggest learning to do it by hand or just get a pair of Knipex Pliers Wrench.

Update 2021-Jul-9: I haven't made one of these for a while, since I discovered the Knipex Pliers Wrench. Not only does it replace an entire assortment of crow's foot wrenches and is more secure, it's better than this for truing a rotor. If you insist on printing a tool, have at it (use plenty of shells to make it strong) but honestly sometimes the best tool is a real one.

I've printed out several of CBiker's great brake disk truing tools but realized that it was too big to print on the awesome little Monoprice Mini printer, so I brought it into SketchUp and resized it so that it'll fit onto the 120mm square build plate of the mini. I also don't use the hole for the magnet but I do like the through hole for hanging it on pegboard, so I ditched the magnet hole and moved the through hole closer to the end. Still has plenty of leverage and is sized exactly the same as the original at the ends.

If you're not familiar with how to use a rotor truing tool, Park Tool has a great video available on PinkBike: Tech Talks: Rotor truing (You might notice a shocking similarity between the DT-2 truing tool and this design.)