This ancient style of puzzle dates back possibly farther than any documented history of it, and is one of the oldest styles of three-dimensional puzzles we know of. The first known record of burr puzzles is from 1698, but Chinese records attribute them to the inventor Lu Ban (507–444 BCE).

Six sticks of nearly-identical shape form an assembled burr puzzle. The unique notches of each burr interlock in a way that’s hidden when the puzzle is fully assembled.

What makes burr puzzles extra challenging is that, theoretically, you can pick any six burrs at random and usually find a way to interlock them. Some puzzles even use duplicate pieces for added complexity.

Notchable

A craftsman with a saw can easily make notched pieces by carving slots perpendicular to the long axis of the burr. Rotate the piece around the long axis for different directions of cuts.

Millable

All notchable pieces can also be made using a milling machine. Mills can also create other geometry including isolated “island” cubes that are impossible with just a saw.

Non-notchable

These pieces can’t be made with a saw or mill, and require a chisel to cut the internal blind corners. They can also be made by gluing parts together to form a complete piece.

I got the basic design of my burrs from Jamie Taylor on Printables, who made 3D models for a specific set of notchable burrs. Puzzle enthusiasts use this set of 25 burrs to create solid burrs without any internal cavities. Unfortunately, his design has errors in the files, so I chose to recreate them manually.

It took some trial and error to find the correct amount of tolerance between pieces. Too little, and the pieces fit too tightly. Too much, and the pieces would simply slide apart. I tried several different options until I found the right one, and then created a three-dimensional template in my CAD software to ensure consistency.

The next (and most important) step was to print a test set and take a long break with a snack and a cup of tea. Important product research, you know. Very important.

After I finished testing the pieces, I designed a storage box to hold all twenty-five of them. Each piece fits into a slot sized to hold it securely but not too tightly, with plenty of room to comfortably pull each piece out. The box has a full lid as well.

Each piece is labeled with its unique identifier number based on Rob Stegmann’s numbering system.

I kept my branding and manufacturing information subtle by placing it on the inside of the lid. This way, it doesn’t distract from the puzzle experience.

Overall, burr sets are my most popular style of puzzle and sell particularly well coming up to the holidays each year. Some customers even like to mix and match between colors for a truly unique gift.