Introduction: Modular Coffee Table (Design Reinier De Jong)
At the beginning of the summer holidays, my youngest son had this sudden idea to make a piece of furniture together. We browsed through my inspiration boards on Pinterest, and we both liked a coffeetable designed by Reinier de Jong from Rotterdam. The purpose of building this together was to have some quality time together, but at the same time I took it as an opportunity to pass on some basic woodworking skills onto the 'smartphone generation'.
I asked him to make a few sketches, based on the raw materials I usually use. Then we turned it into a Sketchup model to work out all the details of the construction and derive a detailed part list.
Further we decided to make it an overall size of 70cm x 50cm (instead of the original 80cm x 60cm), so it would also fit in a smaller apartment or studio. Using 5 'layers' of the 70mm Wenge, would result in about 35cm height.
Step 1: Parts
The coffee table is made from 2 kinds of wood :
- 12 mm Birch plywood (we call it 'Multiplex')
- Solid pieces of Wenge used to cover the edges of the plywood. This makes the corners stronger as well.
The partlist (as ms-excel attachment, further below) gives you the overview of all parts. You will need a total of ~3.6 m² of plywood and ~10 running meters of Wenge.
On top of the wood you will need wood glue (I use Bison D3 waterproof) and wood oil (I use Woca, formerly known as TripTrap).
The table is completely glued, no screws or nails are used. This results in a nice minimalistic design, but at the same time there is no 'undo' possible after glueing, so make sure to always double-check correct part numbers, alignment, proper clamping, etc. Having someone else check your work is very helpful here.
Cost estimate :
- Plywood : 90 €
- Plywood cutting : 30 €
- Wenge : 100 €
- Glue, Oil, Sandpaper, Dust mask, etc. 20 €
Total cost : 240 €
Building this table requires at least 3 days, with an estimated 10 hours of effort.
Step 2: Tools
- A (Miter) saw : for cutting the right length of the Wenge strips
- A router, for flush trimming the excess of Wenge and for routing a few grooves.
- An orbital sander : for cleaning all finished surfaces. Using a grit of 80 up to 120
- Clamps : as this whole project is completely glued (no screws, nails) and as all things need to be straight and square, you need quite a bit of clamps. I used 4 of 120 cm, 6 of 80 cm and a bunch of 30 cm clamps.
And of course the usual tools for measurement : a good tape ruler and square rule.
One last note to tools : when assembling this design, it requires accurate right angles, and perfectly parallel sides. The inner piece is 68 mm thick, and it fits in a 70 mm void. If that 70mm is not accurate, the pieces will either not fit or they will be too loose. So when assembling this you need a really 100% flat surface. I decided to assemble it on the kitchen worktop, as it is made from a thick stone.
Step 3: The Plan
We only had some pictures from the web, no real drawings, so we needed to reverse engineer the project. Here are the main design decisions :
The table consists of three parts. To refer to them in an easy way, I call them the Small, the Middle and the Big part.
I've included a Sketchup 3D model, as well as an Excel spreadsheet with all parts listed, their amount, dimensions, etc. The part numbers in excel match the part names in Sketchup. In the Excel partlist, you can adjust overall dimensions, and the sheet will calculate the dimensions of all parts. (double check if you do this)
As the Wenge comes available in 71 mm wide floorboards, and as you always want a little excess to trim flush, I decided to make the thinkness of the pieces 68 mm. This means 2 sheets of 12 mm plywood with a space of 44m between them. (Initially I considered using 18mm plywood, but then the result would be too heavy. 12mm was strong enough, you could even consider 8mm to make a more lightweight design)
As the Small part needs to fit & slide in the Middle part, the inside of that Middle piece needs to be a bit more. I decided to aim for 2 mm extra, making the inside 70 mm. The same for the Middle vs the Big part : 206 mm fitting with 2 mm of play inside 208 mm.
Step 4: Edge Finishing
Then we needed a solution for the edges of the plywood. You can leave them visible, but then everyone knows it's plywood. You could use miter joints, but you need a good table saw to cut them accurately. Furthermore, the layers of the plywood are only like 1mm each, so the edges would be quite fragile...
I decided to use a piece of Wenge to strengthen the edges. When joining two sheets of 12 mm plywood, a groove of 4x4mm is cut with the router, and a piece of 8x8 mm Wenge is glued at the edge. The pictures show how the plywood is assembled and some Wenge is used to finish the edges.
Step 5: The Small Part
It makes good sense to start with the smallest part, the inner one. Building this is straightforward, and having this part ready is helpful in building the next part, as they have to fit together.
The partnumbers (#) refer to the numbering in the partlist, and the name of the parts in Sketchup. There is one picture for each step below. In each picture, the 'new' parts are coloured, whereas the parts from previous steps are grey.
- put one of the plywood pieces (#1) on the workspace, best side down
- glue the spacers (#2)
- glue the other plywood piece (#1) on it, best side up - check with a carpenter square (or a square leftover piece of plywood) that both sheets are perfectly aligned. Put a weight on it. Double check alignment ! Wait until the glue is dry.
- cut 2+2 pieces of Wenge : 2 for the long sides (#3) and 2 for the short sides (#4). Cut them 1 mm longer, as we will flush-trim them with the router. Put a 1 mm stack of paper (eg. some pages of a newspaper or magazine) on the work area. Lay the piece assembled above onto it, it will now be 1 mm above the worktop surface. Glue the Wenge strips. As they are sligthly wider than the core, and as the core is slightly above the worktop, the Wenge should extend a little bit at both sides. As they are also slightly longer than needed, they will also extend a little at the end.
After glue is dry, all the excess can be flush routed.
Now that was a good warming up off all the skills we need for the serious work : accurate glueing and flush routing!
Let's move on...
Step 6: The Middle Part and the Big Part
The Middle and Big part are more complicated. But by now you have at least some experience from building the Small part, so you should be fine to build them now. Again, (#) refers to part numbers in Excel and Sketchup, and each step has one picture.
- Two of the parts (#9 and #10) need to get a 4 mm groove: part #9 along both long edges and one of the short edges. Part #10 along both long edges only. (See also Step 4 - edge finishing)
- Put one of the inner sheets of plywood (#6), best side up, on the worktop.
- Glue the vertical inner pieces (#7 and #8) as show in the picture and ensure the right distance with the spacers (#11). Again double-check all angles (square) and alignments. Tip: you can use some of the plywood to check square angles. When they are machine-cut the corners should be perfectly square. Put pressure on it with either weights or clamps and let it dry.
- Glue the second inner sheet (#6) on top of it, best side down. This step is critical : you need perfect alignment of both inner sheets (#6), and they have to be nicely parallel. Adjust clamps position and tension in order to get 70mm of clearance between the sheets, everywhere...
- Glue 4 spacers (#12) strips on top and bottom
- Glue the bottom sheet (#5), align with front
- Glue the backs - long side (#9) and short side (#10)
- Glue the top (#5)
- Cut the right lenght of Wenge and glue (#13, #14 and #15)
- Cut the right length of 9mmx9mm Wenge and glue in the ribs. (#16, #17 and #18)
Route with the flush routing bit all excess material
The assembly of the big part is identical, but the dimensions are sligthly larger. The clearance inside this piece is 208mm, as the Middle piece is 206mm thick, resulting in a 2mm gap as well.
Step 7: Finishing
- Sand all surfaces with a grit 120 sandpaper
- Remove dust with a moist towel (making it wet will to some extent open the wood pores, but this is ok as it will allow to oil to better penetrate the wood, resulting in a better protection.)
- Let dry
- Apply wood oil, according to instructions