Tetris-Style Shelf Using Dovetail Joints

In this instructable I'll show you how to make heavy duty tetris-style shelves from wood.

Step 1: What You Need

Saw for straight cuts.
wood boards
wood glue
dovetail cutting jig
router with dovetail bit
square clamps
paper and pencil:-)

Decide for the size.
Most of the tetris shelves I’ve seen on instructables are small and only for light duty (DVDs). I wanted to have them bigger and for heavier stuff:-)
To make the joints really strong I used half-blind dovetail joints.
I made them 30cm deep with a cube length of 25cm.

Getting the wood:
One of the reasons for the size was the availability of wood. I wanted to make as few cuts as possible to reduce error.
I used 7 pre cut and pre planed boards of pine, 200cm x 30cm.

Step 2: Calculate the Board Length

First I started to sketch everything up on paper, to find out, what different size of board I would need. I distinguish between two types and four length of edges:
The two types of edges are inner edges and outer edges. inner edges are connected to one convex vertice and one concave vertex, outer edges are connected to two concave vertices. The length is the number of squares in the tetrominoe that is covered by the edge.
The square piece has 4 outer edges with length 2
the I piece has 4 outer edges, 2 with length 1 and two with length 4
The Z-piece has 4 outer (2 Length 2, 2 length 1) and 4 inner edges (all length 1).
The T-piece has 4 outer (3 length 1, 1 length 3) and 4 inner edges (all length 1).
The L-Piece has 4 outer (1 length 3, 1 length 2, 1 length 1) and 2 inner edges (1 length 1, 1 length 2).

The length in cm of an inner edge is n*a+delta, the length in cm of an outer edge is n*a-d+delta where n is the number of cubes the edge spans, a is the length in cm of one square-element (25cm in my case), d is the thickness of the board, delta is depth of dovetail joint cut (this depends on the diameter of your router bit, I found this out by trial and error, as had no documentation for my jig).

Step 3: Building the Blocks

I prepared templates from the same boards I used for the shelf itself.
There're 6 length I need
length 1 outer
length 1 inner
length 2 outer
length 2 inner
length 3 outer
length 4 outer

I measured them from my calculated values and cut them with my circular saw.

I built 1 L, 1 T, 1 Z, 1 I and two squares. I calculated the number of all the pieces I needed and cut them by using my templates. If you’ve got a table saw, this step can be done pretty fast! I only had a circular saw at hand, so this step took a bit longer.
After cutting all the pieces group them together by shelf-element and lay them out on the floor. Be careful to not confuse inner and outer pieces!

Start cutting your dovetails:-) Take special care to not confuse with cutting directions, especially for the inner edges!

When everything is cut, you can glue up the elements.
Basically you don’t need any clamps when you glue the dovetail joints together, they should be square and fit pretty strong by design. I neverthelesess used square clamps to ensure precision.

Gluing together is quite easy because of the joints.