This is a derivative of JoeyC's awesome thing:34852. Much of this is his wording + my respectful commentary. All I did was add a cavity in the handle to store my extra bits. I also added an end cap.Fully configurable magnetic handle for 1/4" driver bits.(JoeyC intended it for driver bits. From the picture you can see I'm using mine for drill bits, which I use to clean out and dress up small holes in my printing.)JoeyC couldn't find a handle he liked for some metric driver bits, so he designed this awesome one.I like the compound curves in the handle. He clearly paid attention to ergonomics. The handle feels very comfortable in the hand when pressing into your work with the tool.It uses an 8mm magnet to hold the bits in place, and is easy to change to suit your preferences.JoeyC's original instructions follow. I used an old ceramic magnet I had laying around the house. Don't use a rare earth magnet... you'll never get your bits out of the cavity! ;-) Instructions 1) Print.2) Glue 8mm magnet into handle.3) Screw (or unscrew) something!Notes:The OpenSCAD file is easy to change. The variables defined at the top of the file configure the handle. You can change the handle diameter and length, the shape/size of the finger grips, and the size of the magnet used.Also the bit size is changeable to adjust for a tight fit on your printer, or to use different size bits. Note that the hex hole for the bits is draw using a six sided circle so the bit diameter will not match the bit size. A bit of trail and error is needed.The variables are as follows (all dimensions in mm):MagDia: Magnet hole diameter, adjust as needed to get a good fit with your magnet. The magnet needs to slide into the handle so don't make it too tight.BitDia: Driver bit hole diameter, adjust as needed to get a good fit with your setup.BitDth: Depth of hole for bitHandDia: Outer diameter of the handle HandLen: Handle lengthVertDia: Diameter cylinder used to cut out vertical grip slots.VertOff: Offset of vertical slots from outer edge, larger numbers mean a shallower slot.GripDia: Diameter of circle used to creat the grip depression near the end of the handle.GripDth: Depth of finger grip.GripRatioTop: Height to width ratio of oval used to cut the top half of the finger grip.GripRatioBot: Height to width ratio of oval used to cut the bottom half of the finger grip.GripOff: Offset from bottom of the handle to the finger grip.