CNC machine moving ahead

Yesterday I got a whole big bunch of extrusions to make a router table. (Actually I thought I was ordering a single extrusion, so this was a huge disappointment). Anyways I decided to make it work and epoxied them all together.

Today I drilled, tapped, and assembled the finished table for the Y axis of the machine. It was slow going because everything has to move without binding. If anything is out of alignment, the motors won’t be able to move the table and cutters properly and the workpiece would be ruined. But I managed it.


Tomorrow, time permitting, I will work on getting the X axis carriage going.

This last picture shows how this layout will work… once I’m done.

A slight detour (happens all the time)

For a couple of years I’ve been fooling around trying to get a CNC machine happening so I can ‘rough in’ necks. This has become more pressing now because I’ve had some ideas lately about how to make the necks more playable by accounting for how the shape of the closed hand changes as you move up it towards the body of the guitar. As the forearm pivots the hand shape changes.  I think a correctly designed neck profile that accounts for this will both feel better and lead to less fatigue or injury.  To explore this I need to be able to prototype a number of neck profile shapes and try them out. It’s easier to change a CAD drawing and run it than to carve a whole new neck by hand every time; and once I have the shape perfected, I’d like to recreate it. Thus the need for CNC. I’ll still have to do a lot of hand work to make each neck but I’m OK with letting a machine get the wooden block 90% there.  But first I need a machine.

I tried building one from scratch out of plywood and angle iron a couple years ago. I could never get everything aligned properly so things would bind and break. So I bought a kit that is way to small to make a neck but will provide a springboard for getting the kind of machine I need, with modifications.

The first picture is of the base kit. The second is of the same machine but with a taller Z axis. I need a minimum of 6 inches of travel in the Z so the heel block can be roughed in.

This is going to take some time and thought. A lot of both. Plus a bunch of farting around.



Trimmed the top, then routed for the binding.

When the finished soundbox of the Boomer came out of clamps this morning, the tap tone was terrific. The sound is tight and big.

I routed off the lip left by the top, and then routed the top and bottom of the guitar with a special bit for binding. The only trick is to make sure you leave the depth set so the binding (oce glued) stands just proud of the surface of the top/bottom. Then it will sand flush. If the binding is lower than the top/bottom and you sand it flush you end up with endgrain showing and it looks like pre-boiled ass.


I used to use a weird contraption to hold the router perfectly perpendicular to the sides while routing, involving hinges and parallelograms and weird bearings. It was too much. I freehand it now. I find that a man, terrified of ruining several weeks of work and/or taking off a finger, can do as good a job holding a router true and steady as a more elaborate contraption. If I start binding curved tops I’ll need the contraption again, but with a flat top, it’s not needed.

I glued the binding on with about 100 pieces of blue tape and now I wait a day.

The top goes on.

I need more clamps. This is barely enough. It will do, but frankly I’d rather have clamping pressure along every single inch of the seam.

If anybody wants to know what I want for Father’s Day, or any gifting opportunity for that matter, it’s this: more bar clamps.

Top bracing… this will take a few days

I glued the maple bridge patch on here yesterday and now I’m starting the top bracing. I’m using Sitka Spruce, in an X configuration.

This picture is of the first spar of the X.  This involves a lot of careful whittling, lots of patience, taking only a little wood at a time so it hugs the contour of the top and the patch. Here’s the deal: I want this so well mated that only light finger pressure closes the gap between the 2 pieces of wood. If it closes but you’re using clamping pressure, that means there’s unresolved stress in the top. The glue will be fighting that, the wood will be fighting that, and it will affect how the top vibrates. When it’s ready to glue I do clamp strongly but that’s so I get a good bond. The glue won’t be holding the wood in a configuration it doesn’t want to be in. It will just be holding it together.

This is my constant goal with my soundboards: there should be as few stresses unrelated to actually vibrating with the string as possible. That way they vibrate most freely and project the most energy in the sound frequencies the string is producing. Or: such is my theory. With my theories and 5 bucks you can buy a cup of coffee.

In an earlier post I promised to show you how I support the braces. It’s simple: little posts, glued to the sides, which act like columns. Since their grain runs perpendicular to the grain of the side, they also act to prevent splitting.


Notice this brace: it’s Orange Osage. It has to take a lot of stress because the fingerboard will be laying on it, when the guitar is done, and the string tension will be trying to make the neck come up and make that fingerboard collapse the top. The Osage will prevent this.

Orange Osage is a weed tree; it’s hard to find big chunks. It is very hard, very strong, very bright sounding when tapped, very heavy and dense for its volume (so I only use it sparingly, in critical spots like this) , and naturally this color. Some people make tea from it, I believe, but I am not sure which part of the plant they make the tea from. It smells good. I’m the only one who uses it in guitars that  know of. I think some people use it to turn bowls.

A word about the woods I use: I don’t use toxic woods (except a little rosewood).  The wood I use frequently is a food tree– walnut, maple, cherry, osage… on the theory that, If I can eat it or something the tree produces, it’s probably OK to breathe a little of the dust.


Various and sundry odds-n-ends

I caught up the maple-bodied boomer while waiting for the fingerboards…

and today those came, so I am putting together a neck too.

The last thing today is making up a rosette, based on a new pattern I have been working with… using a laser engraver. Once it’s engraved I’ll cut it out.

This one turned out too small, so I re-scaled the image. I’ll try again tomorrow…

I think it will look nice when it’s done. I need the soundhole to be 4 inches for the boomer guitar to breathe properly. I’ll save this one for a smaller-bodied parlor guitar sometime.

Top and more bracing, also a little roadblock.

Light duty day. I sanded the top and cut it down on the bandsaw. Also added another brace to the inside of the guitar, after tap testing it and deciding where it would be best.

Discovered I’m out of fingerboards so there will be a pause in the action until they come. Can’t lay out where the bridge will go until I know where the saddle is going to be, and that’s driven by the fretboard.


Maybe I’ll work on the Maple Boomer this weekend and get it to this point. It’s always good to have more than one going so you can keep things rolling along if you hit a bump.