CNC Router Butterfly Inlay Key

Butterfly Inlay Keys

In this article I’ll show you how to make your own cnc router butterfly inlay key. Referred to as bowtie keys or dutchman’s. Their function, to hold boards together adding integrity and strength. They will also used for aesthetic purposes to add character to the workpiece.


The use of Inlay Keys date back to ancient times. They have been used in the construction of Cairo Dahshur Boats. The boats date back to 2500 BC, one was recovered from the Giza Pyramid. These type of boats were a Khufu ship from Egypt. One is on display at Giza Solar boat museum. It’s believed to have been built for King Cheops, the second pharaoh of the Fourth Dynasty.

Historically, inlay keys were used for repairing cracks in Dutch tabletops around the 18th century. This is where the term “Dutchman Joint” comes from. The keys were installed across cracks in these Dutch tables. They would stabilize the crack and prevent it from ruining this elegant piece of furniture.

CNC Router Butterfly Inlay Key

Over the centuries inlay work has been done by hand. A mallet and chisel for the mortise and a saw for the key. With today’s technology the process has been made simpler. This form of craftsmanship is no different. With cnc this undertaking is more precise, faster and gives way to many design ideas.

Different shapes are designed within CAD software. For this example we’re designing a custom inlay with radius corners. Size, depth and shape are all adjustable.. This is too simple to believe.

CAD Design Software

For the example we’re going to be using Vectric VCarve Pro Software. I will fabricate a key with an inlay toolpath. This tool path function will automatically adjust for the radius of the tool used. For this example I will be using a 1/4 inch end mill. The Vectric website has an informative video on this tooling function here.

Using a pocketing toolpath for the inlay and a profile toolpath for the key will cause sharp corners on the profile cut out. The key will not seat correctly leaving open gaps around the inlay. To avoid these problems I program in the Auto Inlay toolpath function. The auto inlay toolpath function will set all the parameters needed for this function automatically. It alleviates sharp corners period.

Male Inlay Bowtie
Female Inlay Bowtie


The pocketing toolpath for the Inlay function gives complete control for the pockets depth. The material for the pocket is 1.0 inches thick. The pocket’s milled shallower than the bowtie thickness. The male bowtie material used is .500 inches thick. I mill the pocketing toolpath depth .025″ less than the insert. The .500″ thick bowtie will stick up above the pocket only .025″. The inlay steps are now complete.


The assembly for this step does not require much. Wood glue and a rubber mallet is all I use to assemble my inlay. I wait for the glue to dry before sanding. This bowtie insert is sanded flush to the materials surface. No planing or sawing off excess material for the inlay. Removing steps save time in our shop. This is why a CNC Router Butterfly Inlay Key works faster.

Final Thoughts

The inlay design is entirely up to you. The inlay toolpath takes away all the guess work. I have a lot of respect for anyone who does this by hand. It shows a degree of skill not always found today. The cnc router butterfly inlay key does the same procedure, it’s just less personal. When time is of the essence a cnc router will make quick work of things. I utilize this in my shop for this reason. Time unfortunately is money.

Thank You for taking the time to read





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