I recently built myself a CNC router and have been working like crazy over the past two months to produce Christmas gifts for all the family. I decided a tea light holder would be a nice simple weekend project as well as a good utilisation of some of the hardwood offcuts I bought in a mixed selection from a seller on ebay.
Each piece is made from a different type of wood; Ash, Beech, Oak, and Walnut. The offcuts pack I bought contained more wood than this but these woods give a nice contrast and the size of offcuts were favourable for this project, but of course, you can use whatever kind of wood you like. First I'll run through a list of things you will need and then take you through the procedure to produce one puzzle piece; given that they are all identical, this is all you will need to be able to make your own tea light holder.
Wood: As mentioned above, I used Ash, Beech, Oak, and Walnut.
You will need a blank measuring at least 90mm wide and 250mm tall with a thickness no less than 5mm (but a little more is ok). In some cases I had to make my blank from smaller pieces of wood, This was done by gluing pieces together. (More on this later)
Glue: Gorilla brand wood glue is the hero of this story.
Clamps: Super important, I like the ratchet kind.
Router: I used a CNC router for this but it can also be done by hand with a scroll saw or something, I'll talk more about this later.
Sand Paper: Lots of sandpaper, I used 80, 100, 150, 220, 280, and 320 grit. You could use a machine but there is a bit more control in manual sanding.
Wax polish: to finish (Optional)
Step 1: Prep Your Blanks
Each puzzle piece started life as a rectangular piece of wood measuring about 90mm wide, 250mm tall, and about 5mm thick. However, sometimes this was not the case and I had to improvise, for example, I had a strip of Oak wood that was only 50mm wide but was 800mm long, so I cut two strips, 250mm long and glued them together. If the wood is glued together properly and clamped well, it can look and feel like a single solid piece of wood.
Once I gathered and/or glued all my wood blanks I surfaced them on both sides. As each puzzle piece is two layers of the same wood; it is important to make sure the surfaces will come together evenly without gaps. This can be done in a number of ways:
The quickest way is to use a drum sanding machine to sand the surface super flat in a very short time.
You could also use a power planar or belt sander but you have to be careful as it's easy to accidentally create a sloped surface, not to mention a little dangerous as these are powerful tools and the work piece is relatively small.
The final way to plane the surface is to use the router itself. If you're using a CNC router like me, you can simply create a pocket operation over the work piece, pop in a large diameter planing tool and skim off a little wood with each pass until the work is flat. If you're routing by hand then you can also use a planing tool and set the height to just below the surface of the wood and work your way up and down the grain until you have a flat work piece.
Step 2: Cutting
Now you have your blank nice and flat it's ready to go; time to cut the shapes. Each blank will give two shapes which, when glued together, will form a single puzzle piece. The are a number of ways to cut these shapes out. As mentioned earlier, I used a CNC router. For this I simply took the SVG file provided in this instructable and opened it in MakerCAM.com. From here I could generate the tool paths needed and export the g-code. If you're familiar with CNC routers then this procedure should be pretty simple. Outside profile operations for the main outlines and an inside profile operation for the hole.
If you don't have access to a CNC router you can print the provided SVG image on some paper and attach it to your blank and use some other tool for cutting shapes, either a scroll saw or jigsaw or even a manual tool such as a coping saw. SVG files should print to 1:1 scale so there shouldn't be any need to adjust the image, unless of course you wanted to. You will also need to drill a hole for your chosen tool to be able to get into the hole on the top piece.
Step 3: Glue and Sand
Now that we have our shapes, we will glue them together. I use Gorilla brand wood glue, this stuff is just awesome! Spread some around the bottom of the top piece (the one with the hole) and press it to the bottom piece (the one without the hole).
WARNING! : There are two possible permutations in which these parts can be glued together to make a complete puzzle piece! These different permutations will result in differently orientated puzzle pieces! If this is your first piece it doesn't matter too much which you end up with, BUT each piece following this MUST BE THE SAME! If you mess this up you will find that when you come to assemble your puzzle pieces that one or two pieces will be upside down!
A simple way to ensure you are gluing in the correct way is to simply test the piece by attempting to assemble before gluing. Once you're certain you have the correct orientation you can glue and clamp your work.
Once the glue is dry you will need to sand it down. I waited until I had all 4 pieces glued, I then assembled them, secured them to a flat surface and used a belt sander to carefully level all 4 pieces at once. After this I dismantled the puzzle and sanded each piece by hand with 80, 100, 150, 220, 280, and 320 grit paper. Assembling may be a little tight at first but after sanding the pieces fit together really easily. Finally, I finished each piece with some wax polish, applied with a clean rag.
And that's it! Now get some nice tea lights and you're good to go!