Guitarbuilder's "Press a Button and out pops a guitar build" thread inspired me to document my steps at creating a new "Thinline" style body this week with a d-fir top and a basswood core. More and more builders are getting interested in CNC and even a very modest machine can be used to help with guitar building. I happened to have the CNC first and started the guitar thing a year later...it seemed like a good idea. I think that's held up as I'm really enjoying this. "Build Number Two" was also a D-fir top, but it was over some very heavy heart pine. I learned a lot from that work including a really nice burst finish that I remain proud of. Unfortunately, that finish has been marred by something heaving accidentally falling on the body, leaving a massive dent that really isn't repairable without completely destroying the finish. I may yet do that, but I already had the intention of doing more bodies of this style and had the material. So while I was working on other things, I set up to do the deed. The basswood blank was glued up the week before. The material was wide enough for a two-board blank and I used T-88 for the joint. Since it would be topped by the d-fir, it was setup with a 38mm thickness. I have my design and machine instructions setup to cut the body as a two-sided job which keeps everything in perfect alignment. My reference point for x-y zero is in the center of the blank which makes two-sides a whole lot easier to design and cut. So after fastening the basswood blank to the machine's spoilboard, I told the CNC software where the center point was using my machine's laser positioning feature. The next operation was to cut two .25" holes on the y-axis centerline to serve as exact registration points when the blank needed to be flipped over to cut the other side. Note that I'm going to cut the back of the guitar body first and then flip it for the top side operations. Before I do that, I'll take a drill and extend the holes into the machines spoilboard a little more because the protective limits on my CNC don't permit going more than about a quarter inch into the table for safety reasons. The back side only gets a few operations...ferrule recesses, control cavity accommodations and a slight round over at the edges to reduce manual sanding later. First the ferrules...and I left the dust collection hood off for these photos so that the operations can be seen and photographed. Normally, I wouldn't do that. Next the control cavity cover recess and the deeper control cavity get cut. The former is 2.2mm deep and the latter only needs to go in about 7mm because after I flip the blank, the rest of the control cavity can be hollowed out from above and everything stays clean at the edges. These cuts on the bottom use a down-cut end-mill (spiral router bit) which also results in a very clean edge. Lastly for the bottom, the body edge is treated with a round-over cutter to reduce work later with sandpaper. For a double-bound body, this step would be replaced by cutting the necessary recess for the binding just as it will be done with the d-fir top here. So now it's time to flip things over...and this is the reason for the holes I mentioned previously. .25" location pins can be spotted in the holes so that when the blank is flipped over, it's oriented exactly in the reverse from the backside and everything will line up "perfectly" At this point, the "core" of the body needs to be pocketed out for the hollows under the f-hole as well as for the control cavity and wiring channels. All of the cuts shown here in this screen scrape will be "hidden" by the d-fir top when it's glued on. You would do this exactly the same way if you were using a hand-held router with a template. The difference here is that it's all completely done in about 15 minutes, including "human time". This part is way too messy to do without the dust boot, so I waited a bit before taking the photo...you can see that the pockets are nearly done here and are identical to what was shown in the previous image. Only the control cavity remains to be cut and it will be perfectly lined up with the work already done on the bottom side. After completing this cutting...it's time to get the d-fir on top.