Getting Good Inlay Results with Inexpensive CNC Routers

by Jon Sevy

Originally published in American Lutherie #144, 2021



Prices for basic CNC routers have dropped dramatically, to the point where small machines in the “3018” class cost only about $250. The name comes from the workable cutting area of 30CM×18CM, which is too small for cutting many of the parts of a guitar (neck, body outline, and so on), but perfect for creating inlays for the peghead and fretboard. The router can be used to cut out both the inlays (in shell, wood, and other materials) and the pockets into which they will be glued. If you have done this by hand, you’ll know just how exacting and time consuming this work is. I use a jeweler’s saw and bird’s-mouth platform to cut the delicate inlays from mother-of-pearl and abalone, and a Dremel with a selection of fine bits to cut out the pockets, using a high-magnification headpiece so I can cut precisely to the lines. It’s tedious work, especially for the repetitive fretboard inlays, so I was interested to try a CNC router as a way to offload this task.

There are many resources available for getting started with one of these routers, including tutorials and software packages for developing designs and controlling the router. The routers are widely available on Amazon; I purchased a SainSmart Genmitsu 3018 Pro model based on the reviews (Photo 1). Some assembly is required, but it was relatively straightforward to get it up and running. Most routers come with software that can be used to control the machine, but it’s often proprietary and may be somewhat limited in functionality. However, the machines generally use a standard open-source firmware called GRBL, which makes it easy to use other software packages to control the router. Though the software supplied with the Genmitsu router is adequate, it’s Windows-based software and I run Linux on my laptop, so I chose to use the open-source bCNC package instead of the Genmitsu software. But all of these software packages support the two essential operations for router control, which are manual positioning and execution of G-code to automatically drive the router. G-code is a simple text-based language to specify the position of the cutting bit.