Careful cutting yields a clever conundrum
Burr puzzles consist of a number of notched pieces that crisscross and interlock to form a three-dimensional, geometric solid. While the origin of the name isn’t clear, the thought is that the puzzles were named after seed pods that they may resemble. They are both fun and challenging to solve, plus when well sanded and finished, they look intriguing when sitting assembled on a shelf or table. This particular design is made from six pieces of wood, five of which have vee-shaped notches cut across them. Cutting the notches is a straightforward table saw operation, but it needs to be done precisely so the pieces fit together well. To aid with this, make a simple cradle to help hold the pieces as you cut them. For best results, make the pieces from a dense hardwood. The puzzle pieces in the photos are made from sapele.
Order of Work
- Make cradle
- Mill pieces to thickness and width
- Crosscut notches
- Bevel to final length
- Sand, and finish
- Attempt to assemble without peeking
The cradle is key
This project requires a lot of angled crosscutting. To make sawing the necessary notches and bevels safer and more precise, build a V-shaped cradle with an adjustable stop block. Dress a length of 8 /4 stock, and then rip a V-groove down its center. Screw the flange and filler to the stop, as seen in the drawing below. Attach the cradle to your miter gauge. Tilt your table saw blade to 45° and crosscut an angled kerf in the cradle that projects into the V-shape by 1/2". Mark this arrowhead with a reference line, as shown at bottom right. Add a toggle clamp to the stop to hold the pieces while keeping your fingers clear of the blade.
Six pieces, three shapes, one solution
The puzzle is made from six equal lengths of squared stock. Three of the six pieces have two notches cut in them. Two of the pieces have three notches. One has none. After cutting the notches, the ends of all six pieces are beveled twice to cut them to final length. If you need a little help solving this brainteaser, watch the video below.
Tilt and rip. With your table saw blade tilted to 45˚, cut the V-groove in the blank in two passes, leaving the blank 1⁄2" thick at the V’s tip.
Add a reference line. After crosscutting a kerf through the V-groove, mark both slopes with reference lines that align with the tip of the arrowhead-shaped kerf.
Notch, bevel, and finish
Mill two 18"-long pieces to 1-1/16" square, and then cut them into four 4"-long segments, which will yield eight pieces—six for the puzzle and two for test cuts. Wrap a center line around a test piece, and align it with the reference mark on the cradle. Secure the piece with a clamp block and toggle clamp. Make test cuts, adjusting the stop as needed until the two cuts meet at the centerline. After making these two cuts on all but one piece, reset the stop block and make the second sets of cuts to complete these first notches. Next, on two of the pieces, repeat the basic process to cut a center notch in an adjacent corner. A sharp, high-quality combination or crosscut blade will yield notches that need little sanding and make for a better fitting puzzle. To finish the puzzle pieces, bevel their ends to cut them to their final length. Sand all surfaces and apply a clear finish.
Bevel to length. Make two opposing bevel cuts on both ends of all the puzzle pieces. Use your third reference line on a test piece to set up the stop for these cuts.
Remove saw marks. To smooth the inside faces of the notches, adhere sandpaper to the face of a flat scrap with double-faced tape.
