I reached the point in my 12 string stage acoustic build where I needed to cut the channel for the soundhole rosette, and didn't want to shell out the major bucks for StewMac's Dremel router base and circle cutting attachment. So let's see what we can cobble together from a few bucks worth of Home Cheapot hardware and some scraps. If this works out, then I'll order some UHMW plastic to make a better second version. A little bit of brainstorming comes up with a working sketch... Let's see if the MDF is solid enough to take threads. I guess, in retrospect, dropping 30 bucks on that M19-2.0 tap sort of negates the economy aspect of this project, huh? Oh well. At least I've got it now in case I come up with some other cool use for the Moto-tool that would require a weird fixture. That seems to have worked fairly well. I'm not sure about the long-term durability of the thread job, but at least the Dremel fits and tightens down nicely. Got the holes drilled for the steel rods on which the circle-cutting pivot point will ride. And here it is all together. There really isn't enough material for the locking thumbscrews to thread into, so I think I'll epoxy some nuts onto the base and the pivot piece. It's tough to see, but the carrier piece rests on a second set of wingnuts. I also determined that the carrier piece was a tad too bulky, so I trimmed it down on the bandsaw from 3/4" to 1/2" thick. And already a difficulty presents itself: the base and pivot pieces were too big. The minimum radius is a shade over 2", which is too big. So, I took a little off the edges of the base and pivot with the bandsaw, got rid of most of the bulk on the carrier, and epoxied down the aforementioned nuts so the lock screws had something more reliable to thread into. Thus comes into existence the Mark Ia router base, which will get down to just over 1" radius, and is just a hair less unwieldy. Grapbbed a chunk of scrap pine for a quick test run just to prove to myself the thing was function. Still butt-ugly, but yes, functional.