How to Mill PCBs on a CNC Machine

Many of my projects use electronics, requiring printed circuit boards (PCBs). Even if you've never developed electronics, you'll recognize these boards from inside any electronic device you've ever seen. They're covered with electronics and usually green in color (traditionally, board inspections were performs my humans and green provided good contrast).



Although the price of (Chinese) PCB fabrication has dropped considerably over the past decade, it's often beneficial to make this closer to home, saving money and weeks of turnaround time. It's also a fulfilling DIY project if you have the right tools.

Rather than show off a project I've made, in this post I'll explain how milled PCBs are produced using a CNC machine with enough detail that you can try it yourself if you have access to a CNC.

Designing a Circuit

I use Eagle CAD for my circuit design because I purchased a lifetime license back when they offered such things. I believe they still have a free version for non-commercial use, but since they started requiring monthly subscription fees most of the hobby community seems to have migrated to KiCad, an open-source, multi-platform tool. Whatever tool you choose, plenty of tutorials are available online to cover design, which is beyond the scope of this tutorial.



Once you have a design, you'll want to export the layers you care about as a DXF file and import that into your CNC software.

Tools and Materials

All materials can be purchased cheaply from sites like AliExpress, eBay, or, for a premium price, even Amazon.


Firstly, you need copper-clad PCB material. I prefer single-clad, meaning the copper is only only one side of the PCB. If you want to do something fancy, you can try double-clad and worry about the double-sided aligning of CNCing. At the time of writing, a 10-pack of 7cm x 10cm "Single Sided Copper Clad PCB" runs around $7, but the prices have fluctuated upwards quite a bit since the COVID-19 situation started.


For cutting the traces, you'll need at least one PCB V-bit engraver. Now, you may be tempted to purchase a fine 10-degree bit with a sharp 0.1mm tip, but that would be a mistake. Such a fine tip will break nearly instantly and without a microscope you'd never even know it. It'll look fine, but your PCBs will be ugly and won't work and you'll spend hours trying to puzzle out why and when you finally figure it out you'll want to warn others. But you won't be bitter or anything. Okay, maybe you'll be just a little bitter.

What you really want is a 30-degree, 0.2mm tip engraving bit. Tips smaller than 0.2mm will break too quickly and you're not engraving deeply enough for the angle to matter all that much. Search for "PCB V bit" or similar and expect to pay around 35 cents apiece when you buy a set of 10.


You may need a couple different sizes of drill bits depending on what your circuit calls for. Through-hole designs will definitely need these, whereas a pure surface mount design could avoid them altogether. I keep 0.8mm and 1.0mm bits on hand. Despite their size, they last a while unless someone bumps against them. Simply search "PCB 0.8mm" or similar and expect to pay around 20 cents apiece.



Lastly, an edge bit will route the shape of your completed PCB. It's optional since you can simply cut the PCB shape on a scroll saw or by other means, but it's so very worth having this bit. It gives PCBs a professional, finished look to them. These are trickier to search for, but try "PCB edge bit" or see if this link still works by the time you read this. The tip size isn't critical (I have 1.2mm) and these bits last a while. Expect to pay around $1.50 per bit.

Preparing for Milling

It is very important to have a flat, level surface to mill. This means, in additional to leveling your CNC surface, you should ensure the PCB itself is flat. Place it on a flat surface like a countertop and flex it slightly until it lays perfectly flat. You'll find that there's quite a bit of flexibility to the fiberglass substrate.

I like to mill the traces first, since that's the most finicky part. You want to ensure that you're completely cutting through the copper, but not going so deep as to make the traces too small. It also helps to do a lead out, making sure you overcut slightly to avoid any uncut portions at the beginning/end of the trace.



Since there is no silkscreen, I often cut documentation directly onto the board. Drilling is quick and painless. The optional perimeter cut makes the difference between a quick test board (above) and a clean finished edge (below).