I’ve wanted to use my CNC machine to build some guitars, but I didn’t want to spend a fortune on body blanks to ruin while learning and perfecting the process. I decided the cheapest option was to make a bunch myself. (Video at the end)
I went to Wurth wood in Charlotte. I had decided on poplar as a species due to its cost. Wurth has rough-cut wood which comes in various lengths, widths, and an odd way of measuring thickness. I wanted my body blanks to be about 1.75” thick, about 20 inches tall and about 15 inches wide. I knew I’d have to glue two pieces together to get the width I wanted. When I say that the wood from a saw mill comes in various widths, I mean it. There’s no standard width. Any random width they could cut from a tree is what you get.
They also count thicknesses funny. Everything is measures as 1/4 in increments. This is normal for 1/4”, 1/2”, and 3/4” but gets weird beyond that. A 1 inch thick board is called 4/4 for instance. I knew I’d have to plane the wood down to get the desired thickness of 1.75” so I went with a couple 8/4 boards.
They price the wood by the “board foot” which is a volume measurement. For instance, if you have a 1-inch thick panel of 1ft x 1ft, then you have 1 board-feet of wood there. The formula for board-feet is
(width in inches x Length in inches x thickness in inches) / 144 = board-feet
With the wood I got, it was just over 7 inches wide, 8/4 thick and in all was 160-ish inches long. For this I spent about $65. I calculated that I could make 6 guitar body blanks from this. That’s a bit more than $10 each which is FAR cheaper than anything I found online anywhere!
The next step (after getting the wood home of course) was to cut and flatten it. I cross-cut the wood with my circular saw to about 20″ in tall pieces. To make them flat and smooth I had to plane them, but I don’t own (nor can I afford) a planer. The solution is simple. Build a sled and use a router to face off the surface of the wood. The process is simple. Starting with the leftmost picture, you can see the rough wood is warped and cupped a bit. I’ll use my router to flatten the top (2nd pic from the left). Then I’ll flip it so the flat side is down, and use my router to again plane it flat on the other side (rightmost pic). You can’t do this just by eye though. I needed to build a jig to hold the wood and a planing sled to hold my router.
To build the sled, I used some scrap pieces of stuff I had laying around. It was just big enough to fit the wood into it. I used a 2ft by 2ft-ish piece of 1/2 inch plywood and four straight and flat pieces of 1×2. I used wood glue and tacked the 1x2s into place with brads to make two walls. The walls height needed to be higher than the wood was planing.
Next I had a piece of scrap 1/2” MDF. I drilled a hole in the middle a bit bigger than my planing bit on my router, and 3 mounting holes in the pattern that matched my router base. The size of this piece of MDF isn’t terribly important except that it needs to be long enough that the router can be all the way on one side of the jig and the MDF still spans the entire jig. Here’s what I mean:
Here you can see the rough wood blank height (which is about 2 and 1/8th inches thick) is just smaller than the right-side wall of the jig (which I made 2 and 1/4 inches tall). You can see that the bottom edge of the rough wood is hot glued to the jig so it won’t move. I did this with the two shortest edges and that was all I needed.
I found that going vertical allowed me to see the depth of cut. I took about 1/16th to 1/8th of an inch depth cut per complete pass, lowering the router in its base each successive pass if needed. Once I planed down one side, I used a chisel to remove the hot glue holding the board to the jig.
Once I finished one side, I left the router at its current height and sat it to the side while flipping the board. This kept the router at the correct height to start on the other side. I then used a chisel to carefully release the hot glue holding the piece down and flipped it. This method will flatten any board on both sides. You can also rout the edges of the board using this jig to get 90 degree angles on 3 side before flipping the piece. Here’s video describing the process:
I actually used the scariest router bit in the world on my router table to get the edges straight though.
Once the edges are straight, I slathered on some wood glue and clamped them together. I had to use tie-down straps as clamps. To keep the straps from getting glued to the wood I put paper towel between the strap and the wood where the seam was.
The next step was to rout the guitar body shape on the CNC machine about 1/4 inch deep, and then rout the cavities for the neck pocket and the electronics. I’d then use my bandsaw to cut the path of the body blank and use the scariest router bit in the world to clean the edges up. I actually hadn’t do this yet. In fact, I made these blanks in 2017 and they have sat in the garage since.
Things that stopped me are:
- My bandsaw is garbage and can’t cut a straight vertical line to save its life, regardless of how tight the blade is or how slow I go.
- I’m scared of the router bit. Routers are a lot like honey badgers in that they don’t give a …. well you know the rest. They’ll cut chunks out of you much faster than you can imagine and with the giant 2.5″ bit I had, it could easily be deadly.
- You have to build the guitar based on a neck and I’ve never bought a neck to design it around
- I sold the CNC machine… But that’s no real excuse, I could use the Shopbot at Charlotte Latin if needed, or just do it by hand. HOnestly, doing it by hand is how most folks do it and it is a lot faster than me figuring out how to CNC it. I’m terrible with CAD…
- I’m lazy and this was so much work that I don’t want to screw up all 6 of them then have to do all this again. I simply don’t have the time to.
