There is nothing like a simple puzzle to occupy a lazy afternoon. The best types of puzzles are those that are hard to put away, and this project is definitely one of those.
The origin of the tangram has been lost to time, but the first written record appeared in a Chinese publication in 1813. The game, unchanged since its conception, was predominantly played by women and children and as such was not considered important or serious enough to be written about and studied, so little is known of its origins.
A tangram consists of seven small boards, called tans, which can be fitted together to form a myriad of shapes, including birds, animals, flowers, people, and geometric designs. Simple in concept, but devilishly complex in execution. You can create your own puzzles, or download samples from the internet. Note that some tangram puzzles require that you use two sets (14 tans).
The basic tangram is made by dividing a square into 16 equal squares and then drawing in diagonal lines to define the shapes of the seven tans. The size of the puzzle is a matter of personal preference, but bear in mind that the smaller the pieces, the more difficult it will be to rout them safely. This little game is addictive and you will soon find yourself with requests for additional sets. So it’s best to prepare for the inevitable request by making a set of accurate patterns in Baltic birch plywood and then using the templates, in combination with a flush trim bit and a special fence on the router table, to make the tans. This version is based on a 6″ square.
• Draw the grid for the tangram on a piece of graph paper and use a pair of scissors to cut the tans shapes out. Using a spray adhesive or double sided tape, glue the individual pieces to some ⅜” Baltic birch plywood.
• With the patterns glued to the stock, use a scroll saw or fret saw to cut up to the edge of the patterns, and then use a disc or belt sander to sand right up to the edges. Repeat this for all of the parts until they fit together without any gaps; keep the edges clean and smooth, as every imperfection will be transferred faithfully when you rout the tans. You may want to mount a small knob in the center of each template to make it easier to hold them.
This is a great project to reduce the clutter in your scrap bin. Like most woodworkers, I find it hard to throw out small pieces of wood, and so have amassed a collection of various off-cuts from past projects.
That is what I used for this project. If you don’t have enough pieces on hand, this project is a great way to experiment with new exotic woods; you can make three tangrams from one board foot of material, so try an exotic species that you have never used before.
• Sand the two faces of the stock while it is still larger as this prevents the edges of the individual pieces from being feathered and rounded over excessively.
• Fasten the templates to the stock with double sided tape, and using a scroll saw or fret saw, cut out the individual tan shapes. Try to stay as close to the guide piece as possible; leaving a minimum of material to trim off will greatly reduce the number of pieces lost to excessive chipping or tear-out.
To safely rout these small pieces on the router table you will need to use a custom fence. These pieces are small and awkward to handle without this fence, so DO NOT ROUT THE PIECES FREEHAND. The fence is simply a straight edged piece of wood with a rabbet cut on the underside and a notch cut out for the router bit. Place a shim slightly thicker than the stock under your router fence and close up the fence on the bit. Then place a clear guard over the bit. That way, there will be no cutting edge exposed (which might pose a danger to fingers) when you trim the pieces flush.
Use auxiliary fence for safe routing.
With the fence set up, take a look at each piece before you trim it. Every piece will have at least one corner where the short grain runs diagonally across a point and this is where the majority of your pieces will chip and be ruined. I chipped several pieces until I replaced my old two-cutter flush trim bit with a three-cutter version from Freud, and used a slower feed rate. Once all the tans are trimmed, ease the edges with some sandpaper. You can leave the tans natural or apply a finish. For a solid colour set, apply a coat of milk paint and wax.
If you wish to let the natural beauty of the grain show through, simply give them a coat of wax. I found that there was no way to avoid burning some of the edges as the pieces were trimmed. Any sanding to remove the burn marks would have altered the shape of the piece, so I opted to ‘ebonize’ the edges using a felt tip pen.
This presented a bit of a problem as the wax applied afterwards acted as a solvent for the pigment from the pen. To avoid getting black fingerprints on a light coloured wood, use paper towels to wipe off the wax without cross-contaminating the two areas.
With the tangram complete, clear off your desk, brew yourself a cup of tea and explore some of the many shapes you can make with this simple game that has captivated people for hundreds of years.