Giant Puzzle / Little Table

You may have seen the Hashtag puzzle, this is a giant hashtag puzzle, that doubles as a little coffee table, or maybe a set of shelves. A little bit of a challenge to make, and assemble but very difficult to disassemble That would be the puzzle part. Great for when you have boring guests to amuse, "Hey I bet you can't pull my table apart, no tools required"

The plywood I made it from was used and water-damaged so there are a few marks and nail holes. I like working with old used wood, but I know its not to everyones taste.

Step 1: Template DXF File

As I'm getting students to make this project I cut out a template from thin plywood on a laser cuter. You could just as easily print the puzzle on paper or mark it out by hand if you are accurate with your measurements The plywood I'm using is 15mm thick, you may have to scale or alter the drawing if you are using a material with a different thickness.

Step 2: Cutting Out and Marking Out the Pieces

Depending On the skill of the students I either cut a strip of plywood, and give to the students or cut into rectangles with the table saw and radial arm saw. Students depending on their age can either cut out with a hand saw, or a machine. I found the Japanese pull saw gives the best results and students find them easier to use than a push-type saw.

The template can then be traced around with a sharp pencil, there and two sides with a hole in the middle and two without. They are two sides different from the other two sides the hole is there just to make it easier to identify which piece goes where

Step 3: Do the Easy Stuff First

I tell the students to do the easy stuff first this gives them a great start, and they get used to using the equipment and they feel like they have made some progress.

Start with drilling some holes two large holes and smaller ones in the corners of the triangular cut-outs so the jigsaw blade can pass through.

It is best to do this on a drill press, drill half way and flip the plywood over, to prevent the chip out on the backside. In the photos you can see I used a hole saw but a spade bit or Forstner bit will work just as well or better. The plywood I'm using is a little water-damaged which has discolored part of it.

Step 4: The Triangle Cut Outs

The next step is a little more challenging cutting out the triangles, I used a Jig saw with a fine-pitch blade, and then filed and sanded the saw cuts. Depending on the maturity of the student they may be able to use a router with a round-over bit to tidy up the edges, or a file and sandpaper will get a similar result but will take a lot more time and persistence.

Step 5: Do the Hard Bit Last

It may be surprising that the hardest part of this project is cutting the slots. Getting the slots straight and the correct size with a jigsaw is quite a challenge and I would recommend that you not use a jigsaw unless you are some sort of jigsaw wizard. A handsaw or maybe a bandsaw are the better options. Once the two lines are cut the waste can be knocked out with a sharp chisel.

Step 6: Sanding and Test Fit

Getting the slots to fit nicely is the most challenging part of this project, You want the slots to fit into the thickness of the material without having to wiggle them or pushing on the parts. If too loose the project won't look any good and will not be much of a puzzle. You want to go for a loose snug fit. I gave the project a quick sand at this stage just knock of any high spots and splinter. Assembling the puzzle is a bit hard to describe, so look at the photos, taking note of where the sides with the holes are. Also, the side without holes have a long slot and a short slot. fit the long slot into the side with the hole, as shown in the first photo before trying to fit all four sides together.

I was a bit annoyed that once I assembled the puzzle I could not get it apart again. Took me a good 40 minutes, Ive always found these puzzles are far more difficult to pull apart than assemble, the large scale made it even more of a pain!

Step 7: Optional Top

Next, cut a small square to fit in the top of the puzzle this will strengthen everything up and make it suitable for a table, or stool. The top was made out of another scrap piece of plywood I had lying around, and the small square was glued to the underside of the tabletop. This makes the top removable so you can use it as a puzzle whenever you want. Just cut out the size that you want and round off the corners, The phots show that I used a roll of tap to trace around.

Step 8: Final Sand and Finish

As the puzzle will be handled a lot It is important to make sure that everything is smooth and free of sharp edges and splinters. so I sanded with 80, 120, 180, 240, then gave the project a clean and coat of timber polyurethane finish. The project was left to dry for 6 hours and then another sand with 400 and another coat of polyurethane.