I was moving to a new apartment and found myself in need of a new coffee table. I wanted to make something unique, but not impossible to make with the relatively limited tools at my disposal. Fortunately, I had just signed up for a few months of membership at my local TechShop here in Pittsburgh, so I now had access to a ShopBot CNC router. After a quick google search, I had a couple designs I was interested in mimicking (I don't even try to pretend I have the creativity needed to make something aesthetically pleasing). I eventually settled on the Cross Coffee Table, a discontinued model from Design Within Reach. It was stylish and made only from flat components, allowing me to cut everything from one piece of wood.
Step 1: Gather Materials
Solid wood legs proved to be rather expensive, so I settled upon 3/4" oak veneer plywood. A 4' x 8' board is about $50 at home depot, and you really only need half (4' x 4') if you're careful. In addition you'll want to get some:
- 80, 150, and 220 grit sandpaper
- tack cloth to remove dust from sanding (this step is really important, don't skip it)
- Wood conditioner (this goes on before the stain, and helps the wood accept stain uniformly, which is especially important for plywood).
- Your wood stain of choice. I went with a light oak gel stain that combines the stain and polyurethane steps, reducing the amount of drying time and number of steps.
- Polyurethane (if you don't get a combination stain).
- Wood glue (optional)
Step 2: Prototype
To make sure the parts would look right and fit together correctly, I resized my drawings for a very small scale version and got a friend (who was checked out on the laser cutter) to laser cut the parts for me. Then I tried a slightly larger scale version on the shopbot using some plywood.
It is very important that you accurately measure the thickness of the wood you will be cutting, as the slots at the center of the leg pieces must be exactly as wide as the material's thickness in order to fit snugly together. It is also important to incorporate fillets into the slots. These make sure that the router will cut all the way down to the bottom of the slot (this is an issue with making any sort of rectangular slot using a round cutting tool). If you don't make fillets, then the pieces won't slide together all the way and the four feet of the table won't be flush against the ground.
Step 3: Cut the Wood
Attached are the CAD files I used to draw and cut the table legs on a ShotBot Alpha at TechShop Pittsburgh. You need to import them into VCarve Pro or some other program that can make cutting paths for the shopbot. From there, test cut the file before actually cutting into your wood. Make sure the wood is tacked down in enough places to prevent it from bowing, which can cause the cutting bit to remove too much wood in a given pass, placing undue stress on the bit.
Step 4: Sand and Stain
Give the edges and corners a good rubdown with 80 and 150 grit sandpaper, followed by tack cloth, followed by 220 grit and more tack cloth. I found that the veneer was smooth enough that it only required a quick once-over with the 220. Make sure you get rid of all the dust before applying the wood conditioner (follow the instructions on the can). Let it dry overnight in a well ventilated area, then begin applying the stain. In my case, I used a two-in-one stain and polyurethane (Minwax "gel stain"). I found that this stuff dries very quickly, so you must work fast to apply a nice even coat (watching out for drips). Let each coat dry overnight. I applied two coats total, and used 220 sandpaper to smooth out the first coat after drying. After a very thorough rub down with more tack cloth, I applied the second coat and waited another day.
Step 5: Assemble
Depending on how well you measured the thickness of your wood (I measured in multiple places with calipers and took the lowest value), your pieces will probably fit a little too snugly together. Especially if you're messy like me and allowed some polyurethane to drip into the slots. Sand away like a madman until those suckers just barely fit together. I found that a rubber mallet and some scrap wood did the trick. Lay the scrap wood against one of the legs so you won't leave marks on your nicely finished surface, and gently (or not so gently) tap the two pieces together. I made the decision to rub a thin layer of wood glue into the slots before assembly. I opted for stability rather than the ability to disassemble the table later. With a tight enough fit the glue shouldn't be necessary, but I would guess that the fit will gradually get looser the more you take it apart and put it back together.
Finally, contact your local glass shop to acquire a glass table top. They generally have many standard square sizes available with a variety of edge styles and finishes. For this base, I chose a 3/8" thick, 36" square piece with polished edges and 90 degree corners. Rounded corners would probably also look fine. I also bought some adhesive, clear rubber bumpers to put between the legs and the glass, to keep it from sliding around. The total materials cost came out to about $200, but I still have a 4'x4' chunk of plywood, and enough wood conditioner and stain to redo this project 10 times over, so I would say the real cost was about $140, with $115 of that being for the glass surface.
The .dwg file is attached, but remember to adjust for your particular wood thickness, cutting tool, and any other stuff I may have forgotten. Be safe, and enjoy your new coffee table!
I made it at Techshop! (shameless plug, yes, but it really is an awesome place)