Makernaut developed and published this great 3d printable rotary tool or Dremel. It looks easy to make even with entry level electronics skills and has three 3d printed enclosure parts.
It is powered by 12V DC motor (listed as 6000 rpm, RS-550S motor, diameter~37mm), it has PWM DC motor controller (3A) and mini chuck / collet set for 3.17mm shaft to hold the tool bits.
Here is the build guide video with a short demonstration:
Full Instructables with STLs and parts list can be found at:
You can also go and see Makernaut's youtube channel: