Note that this was designed for the original MPCNC Z rail mount. This won't fit the newest MPCNC version "525"
Makita rt0701c 1.25 HP variable speed compact router tool mount for the wonderful Mostly Printed CNC. The holder is sized for US EMT conduits.
This router is much more powerful and much quieter than the Harbor Freight flexshaft grinder and is variable from 10K to 30K RPM. Note that the Makita only comes with a 1/4" collet. I got a high quality 1/8" collet from: http://www.elairecorp.com/makitaroutercollets.html. It supposedly has a very low runout. A 1/4" to 1/8" reducer can also be used. The weight is 3lb 1oz.
The clamp holes should fit #6x3/4" or M3x18mm bolts. This was my first Autodesk Fusion 360 design so I did not try to get too fancy. Next time I will try for captive nuts. The Fusion 360 source is included. I'm proud of how close I got the spindle center to the Z axis. There is really only 2mm or so to spare! A tradeoff is that the on/off switch is a bit hard to get to depending on the Z position and the rotation of the router. The speed control dial is easily reachable.
Printed at 0.3mm/layer, 30% infill in PETG from the Microcenter (Cambrige, MA store). About 4 hours to print on a Robo3D with an E3DV5.
Thanks for inspiration from shnads' metric tube mount: http://www.thingiverse.com/thing:1008647.
Update (11/8/15): I suggest mounting it upside down from the position in the photos to slightly reduce the Z length and associated torque. I am also now using Camar0's Middle Rigid Bracket Add on and Allted's Middle Z Ridgid. See: http://www.thingiverse.com/make:169149
Update (12/14/15)): I jury rigged a simple vacuum hose holder by extending the three screws to hold a 1.5x3.5 piece of thin hardwood plywood. A piece of PVC pipe was tie wrapped to the plywood. Used a file to groove the pipe in three places for the tie wraps to grip better. A 1.25" vacuum hose fits into the pipe. I velcroed a clear piece plastic (acetate?) from a box window to guide the airflow.
See build photo in: http://www.vicious1.com/forum/topic/cosx2y2-milled-in-wood-post-1/